Experimental Particle Physics at HERA and LHC Scientific Section ...

Experimental Particle Physics at HERA and LHC
Scientific Section
Contents
1 Summary 2
2 Research plan for H1 3
2.1 ep collisions at high energies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Early results from HERA II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.3 Status of HERA and H1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.4 Summary of activities of our own group . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4.1 Operation of the CIP2k system in the H1 experiment . . . . . . . . . . . . . . . 6
2.4.2 Analysis projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4.2.1 Excited quarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4.2.2 Prompt photon analysis in DIS and photoproduction . . . . . . . . . . 8
2.4.2.3 Isolated τ leptons in events with large missing p T . . . . . . . . . . . . 10
2.4.2.4 Search for Lepton Flavor Violation . . . . . . . . . . . . . . . . . . . . . 12
2.5 Research plan for 2005/2006 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.6 Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.7 Relevance of proposed research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.8 Publications and references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.8.1 Articles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.8.2 Articles in print . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.8.3 Conference contributions, presented by group members . . . . . . . . . . . . . . 16
2.8.4 Contributed papers to conferences . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.8.5 Theses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.9 H1 as international collaboration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3 Research plan for LHCb 19
3.1 Status of CP-violation and the physics of B mesons . . . . . . . . . . . . . . . . . . . . . 19
3.1.1 CP violation within the standard model . . . . . . . . . . . . . . . . . . . . . . . 19
3.1.2 Experimental results from B factories . . . . . . . . . . . . . . . . . . . . . . . . 20
3.1.3 CP violation and physics beyond the Standard Model . . . . . . . . . . . . . . . 21
3.1.4 LHCb: A second generation b-physics experiment . . . . . . . . . . . . . . . . . 23
3.2 Status of our own work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.2.1 The Silicon Tracker project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2.2 Silicon sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2.3 Detector modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.2.4 Module Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.2.5 Station mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.2.6 Digital optical readout system for the LHCb Silicon Tracker . . . . . . . . . . . . 31
3.2.7 Detector simulation and track reconstruction software . . . . . . . . . . . . . . . 33
3.2.8 Monte Carlo event production using the computing grid . . . . . . . . . . . . . . 33
3.2.9 The event filter farm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.2.10 Preparation for physics analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2.10.1 Data analysis of rare B s decays at Tevatron . . . . . . . . . . . . . . . 35
3.2.10.2 The process Bs 0 → J/ψη ′ . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2.10.3 B c decays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.3 Research plan for the forthcoming period . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.4 Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.5 Investment plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.6 Publications of the Zürich group on LHCb and B physics . . . . . . . . . . . . . . . . . 42
1

1 Summary
We are submitting a request for continuing support for the participation of Universität Zürich in the
H1 - Collaboration at HERA-II, as well as for the installation and commissioning of a detector to study
CP violation and B meson physics at the LHC.
HERA: During the nine years of successful operation of the HERA storage ring, which ended in the
year 2000, the H1 - detector has studied collisions of 27.4 GeV electrons and positrons with up to 920
GeV protons with a total luminosity of ≈ 200 pb −1 . During this phase (HERA-I) both the H1 - and the
ZEUS - Collaboration have explored the structure of the proton and tested quantum chromodynamics
(QCD) predictions focusing on precise determinations of the neutral and charged electroweak current
cross sections at high momentum transfer leading to parton density functions in pre-HERA inaccessible
domains of Bjorken x and momentum transfer Q 2 , diffractively produced final states, hidden and open
charm and beauty production as well as searches for states outside the Standard Model.
Since the HERA-I luminosity was insufficient to obtain large event samples for electroweak processes at
the highest momentum transfers (Q 2 ≈ MW 2 ) an upgrade program was started in 2000 and completed
in 2001. After solving a series of technical difficulties, which required another longer shutdown in
2003, the luminosity and lepton polarisation has now reached design values and tolerable background
levels in the H1- and the ZEUS-detectors. During the beam period 2004 and 2005 almost 100 pb −1
of polarised electron proton collison data was taken. Present plans call for HERA-II running until
2007, with an expected integrated luminosity of ≈ 500 pb −1 , split between electrons and positrons of
both polarisations each. This will considerably raise the discovery potential of the HERA machine
and detectors for beyond the standard model physics in the largely unexplored mass region above 200
GeV/c 2 and lead to considerably enlarged high Q 2 event samples. First analysis results of HERA-II
data are available.
The Swiss part of the H1-team comprises also ETH-Zürich (Prof. R. Eichler, Dr. C. Grab and group
members) as well as PSI (Dr. S. Egli, Dr. R. Horisberger and group members), with whom traditionally
a close collaboration is cultivated.
LHCb: LHCb is a second generation experiment on b quark physics, which will start data taking
at the beginning of LHC operation in 2007. The goal of the experiment is to perform systematic
measurements of CP violating processes and rare decays in the B meson systems, with unprecedented
precision and in many different decay channels of b quark mesons. Measuring CP violation in numerous
decay modes of B 0 d and B0 s mesons and comparing the results with predictions from the Standard Model,
the experiment will search for new physics.
Our group at Universität Zürich concentrates on the development, construction, operation and data
analysis of the LHCb Silicon Tracker, as well as on the preparation for physics analyses. The Silicon
Tracker is a large-surface, wide-pitch silicon detector that will be used in the online triggering and in
the offline reconstruction of charged-particle trajectories in the LHCb spectrometer. R&D on detector
components for the Silicon Tracker has been completed last year. Mass production of detector elemeents
and mechanical supports has started and is expected to last until the end of 2006.
In addition to our group, the École Polytechnique Fédéral de Lausanne, the University of Santiago de
Compostela (Spain), the Max-Planck-Institut für Kernphysik, Heidelberg (Germany), the Budker Institute
for Nuclear Physics, Novosibirsk (Russia) and the Ukrainian Institute of Science, Kiev (Ukraine)
are members of the LHCb Silicon Tracker group. However, most activities are concentrated in Zürich
and Lausanne.
The LHCb Silicon Tracker project as a whole is coordinated by us (O. Steinkamp and U. Straumann).
It represents a significant Swiss contribution to the LHCb experiment, that is clearly visible and well
recognized in the international particle physics community.
Keywords: Particle physics, ep - collisions at 320 GeV, H1 collaboration at HERA, b quark, B meson,
LHCb, CP violation, CKM matrix, Standard Model, new physics.
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2 Research plan for H1
2.1 ep collisions at high energies
The analysis of the HERA I data (1999/2000 L = 91 pb −1 , pre-1999 L = 50 pb −1 ) lead to 15
publications ([P1]-[P15]) and 23 additional papers contributed to the high-energy physics conferences
of the summer 2005 ([P19]-[P41]). Some papers of the latter group already deal with HERA II data
(2003/2005 up to L = 115 pb −1 ) ([P19]-[P22]). One of our graduate students completed his thesis
([P42]). Two group members have given invited talks at international conferences ([P16]-[P18]).
These publications address the following subjects:
- Neutral and charged electroweak current cross sections, proton structure functions and parton
densities (extensions to low Q 2 and high x using radiative events), now including data from polarized
electron and positron beams [P12,P16,P19,P20,P21]
- Search for states and interactions outside the Standard Model: unexpected event topologies [P1,
P33, P35], gravitinos [P9], leptoquarks and leton flavor violation [P11,P17,P18,P22,P26], charged
Higgs [P24], anomalous lepton pairs [P1,P33], magnetic monopoles [P4], excited fermions [P42];
- Photo- and electroproduction of di- and multijets, including a determination of α s [P5, P14, P23,
P25, P32, P41];
- Photo- and electroproduction of exclusive final states: ρ [P37], J/Ψ [P15] and strange pentaquark
(search) [P40];
- Photo- and electroproduction of open charm and beauty, now dominated by analyses making use of
the central silicon vertex detector built by the Swiss groups: clarifying evidence for an anti-charmed
baryon state [P39], charm [P3,P7,P8,P13,P27,P28,P29,P30,P34], beauty [P6,P7,P8,P13,P27];
- Diffractively produced final states [P32,P34,P36,P37,P38];
- Photon structure [P2] and deeply virtual Compton scattering [P10].
The contributions from HERA-II data taken deal with events containing high transverse momentum
particles (p T > 25 GeV/c) [P33,P35] and the measurement of polarisation dependence of the total
charged current cross section [P19,P20]. We have reported on the latter subject in our annual progress
report [9] and summarize the findings of the former subject in Sec. 2.2). Further reports deal with the
ongoing analyses of group members (Sec. 2.4.2).
2.2 Early results from HERA II
The H1 Collaboration has previously reported the observation of events with energetic isolated electrons
or muons associated with missing transverse momentum [1]. The analysis included the full HERA I
data sample corresponding to an integrated luminosity of 118.4 pb −1 . In the HERA I data, 11 electron
events and 8 muon events were observed compared to a Standard Model (SM) expectation of 11.5±1.5
and 2.9 ± 0.5 respectively. At large hadronic transverse momentum PT
X > 25 GeV, 5 electron events
and 6 muon events were observed compared to a SM expectation of 1.8±0.3 and 1.7±0.3, respectively.
The update of the published analysis includes the new e ± p data sample accumulated at HERA II from
October 2003 to May 2005, corresponding to an integrated luminosity of 92 pb −1 .
Signal events are defined as those that contain a prominent high P T isolated lepton accompanied by
genuine, large missing transverse momentum. The main SM process that may produce events with
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this topology is the production of real W bosons via photoproduction with subsequent leptonic decay:
ep → eW ± (→ l ± ν)X. Additional, smaller contributions arise from the production of W bosons via
the charged current process ep → νW ± (→ l ± ν)X and, contributing only to the electron channel,
the production of Z 0 bosons with subsequent decay to neutrinos ep → eZ 0 (→ ¯νν)X. The main SM
background to events containing isolated electrons arises from neutral current (NC) events, where fake
missing transverse momentum is produced by a fluctuation in the detector response, and from charged
current (CC) events, where a particle in the hadronic final state or a radiated photon is interpreted
as the isolated electron. For events containing an isolated muon the main SM background arises from
lepton pair (LP) events, where one muon escapes detection and mismeasurement causes the apparent
missing transverse momentum, and from CC events where, similarly to the electron channel, a particle
in the hadronic final state is interpreted as the isolated muon.
Electron Muon Combined
H1 preliminary obs./exp. obs./exp. obs./exp.
(Signal fraction) (Signal fraction) (Signal fraction)
1994-2004 e + p Full Sample 19 / 14.6 ± 2.0 (70%) 9 / 3.9 ± 0.6 (84%) 28 / 18.5 ± 2.7 (73%)
158 pb −1 PT X > 25 GeV 9 / 2.3 ± 0.4 (80%) 6 / 2.3 ± 0.4 (84%) 15 / 4.6 ± 0.8 (82%)
1998-2005 e − p Full Sample 6 / 5.8 ± 0.9 (62%) 0 / 1.5 ± 0.5 (76%) 6 / 7.3 ± 1.4 (65%)
53 pb −1 PT X > 25 GeV 2 / 0.9 ± 0.2 (71%) 0 / 0.9 ± 0.2 (73%) 2 / 1.8 ± 0.3 (72%)
1994-2005 e ± p Full Sample 25 / 20.4 ± 2.9 (68%) 9 / 5.4 ± 1.1 (82%) 34 / 25.7 ± 4.0 (71%)
211 pb −1 PT X > 25 GeV 11 / 3.2 ± 0.6 (77%) 6 / 3.2 ± 0.5 (81%) 17 / 6.4 ± 1.1 (79%)
Table 2.1: Summary of H1 results on searches for events with isolated electrons or muons
and missing transverse momentum for e + p data, e − p data and the full HERA data set. The
results are shown for the full selected sample and for the subsample at large PT
X > 25 GeV.
The number of observed events is compared to the SM prediction. The signal component of the
SM expectation is given as a percentage in parentheses. The quoted errors contain statistical
and systematic uncertainties added in quadrature.
The full data sample corresponding to an integrated luminosity of 211 pb −1 now yields 34 events
(for details see Table 2.1) compared to a SM prediction of 25.7 ± 4.0. At large hadronic transverse
momentum PT
X > 25 GeV 17 events are observed compared to a SM prediction of 6.4±1.1. In 9 events
the lepton charge is positive, in 4 events negative and unmeasured in the remaining 4 events. The
probability for the SM expectation to fluctuate to the observed number of events or more in the high
PT
X domain is 0.0012 compared to 0.0015 for the HERA I data alone. The kinematical distribution
shown in Fig. 2.1 does not provide any further clues. The continued increase in luminosity expected
from the HERA II programme in the coming years will hopefully clarify the situation.
The production of multi-leptons at high transverse momenta has been studied, too, for the HERA-II
data. The measurement extends previous analyses [3, 4] and corresponds to integrated luminosities
of 45 pb −1 and 40 pb −1 for e + p and e − p, respectively. The event yields in the di-lepton (ee, µµ and
eµ) and tri-lepton (eee and eµµ) sub-samples are in good agreement with the SM predictions. The
distribution of the scalar sum of transverse momenta of the leptons is studied for the combination of all
di- and tri-lepton sub-samples. For P T > 100 GeV 4 events are observed and 0.81 ± 0.14 are expected.
The general search for new physics involving high P T particle production consists of a comprehensive
and generic search for deviations from the SM prediction using all high P T final state configurations
involving electrons (e), muons (µ), jets (j), photons (γ) or neutrinos (ν). The analysis covers phase
space regions where the SM prediction is sufficiently precise to detect anomalies and does not rely on
assumptions concerning the characteristics of any SM extension. Such a model-independent approach
may discover unexpected manifestations of new physics. Results obtained with HERA I data (L = 115
pb −1 ) have previously been published [P1]. The results from part of the HERA II data sample (L = 55
pb −1 ) are now avalailable, too. As in the HERA I analysis, all final states containing at least two of
the five objects with P T > 20 GeV in the polar angle range 10 ◦ < θ < 140 ◦ are investigated. All
selected events are classified into exclusive event classes according to the number and types of objects
detected in the final state, for example ej, µνj, jjjj. Good agreement with the SM expectation is
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Figure 2.1: The hadronic transverse momentum distribution in the electron and muon channels
combined: data (HERA e ± p, L = 211 pb −1 ) is compared to the SM expectation (open
histogram). The signal component of the SM expectation, dominated by real W production, is
given by the hatched histogram. NData is the total number of data events observed, NSM is
the total SM expectation. The total error on the SM expectation is given by the shaded band.
observed in all event classes, indicating the good understanding of the SM predictions for HERA and
of the H1 detector in the HERA II configuration. The majority of the events observed in the dedicated
multi-lepton and isolated lepton analyses are also selected in this general analysis.
2.3 Status of HERA and H1
HERA-II is operating since end of 2003 and has reached its design instant luminosity during 2004.
Presently routine luminosity production of HERA allows standard data taking at H1. While the first
period of HERA-II running was devoted to positrons, since end of 2004 polarized electrons and protons
are being collided. HERA-II is scheduled to be operational until mid of 2007. We hope to be able to
acquire large ep data sets of all four combinations of lepton charge and helicity until then.
During periods of good operation conditions, HERA produces luminosity fills which last for typically
15 hours and produce 1 pb −1 integrated luminosity. H1 is presently able to use about 70% to 80% of
this beam to produce good data. The losses in H1 are mainly due to restricted HV operation of the
drift chambers at the beginning of the fills, when background conditions are bad. Possible improvement
in operation and in the vacuum quality are being investigated. Figure 2.2 shows a typical two day
operation period of HERA.
Unfortunately in practice there are still a lot of down times on the HERA machine due to all kind of
different technical problems. So far the average availability of the machine in 2005 did not exceed 30%,
as it has been ever since HERA became operational in 1992. Although other colliders do not perform
much better, it is still believed, that things could be improved significantly with a large effort of much
more automated system control of the technical equipment for instance magnet and RF power supplies,
vaccum system etc. Another source of problems originate from damages of various equipment due to
strong synchrotron radation at various places of the machine, which often result in vacuum leaks.
The H1 experiment itself performs very well. About a dozen subdetectors run routinely with high efficiency
and well understood calibration. Regular, mostly automated data quality checks and calibration
data runs are overviewed by the operation crew.
Until the beginning of the winter shutdown in November we expect a total of 100 pb −1 of polarised
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Figure 2.2: Two days of successful HERA operation in early September 2005. Proton and
electron currents are shown in blue and red, respectively. The green curve shows the lifetime
of the electron beam, which tends to improve towards the end of a lumi run. When the electron
current has decayed below a certain threshold, new protons and shortly afterward new electrons
are filled into the collider. The downtime between fillings can be as short as half an hour.
electron proton data being stored by H1 during the year 2005, resulting in about equally large available
data sets of e − p and e + p data.
2.4 Summary of activities of our own group
Members of the research group:
- Dr. Katharina Müller, Dr. Peter Robmann, Prof. Dr. Ulrich Straumann, Prof. Dr. Peter Truöl,
Dr. Stefania Xella Hansen
- Ph.D. students: Linus Lindfeld, Carsten Schmitz, Krzysztof Nowak.
2.4.1 Operation of the CIP2k system in the H1 experiment
The CIP2k multi wire proportional chamber (MWPC) which was developed and built at Universität
Zürich is fully operational for the H1 experiment since more than two years now. As an essential part
of the H1 trigger system, the CIP2k trigger elements successfully reduced the larger background from
HERA II on the first trigger level (L1) as it was anticipated.
By now the CIP2k system became efficient and useful for many trigger combinations. Up to now CIP2k
trigger information was included in 42 out of the total of 83 trigger combinations used in H1. It is
evident, that a successful operation of the CIP2k system has become vital for H1 data taking and the
good system performance is highly recognised by the collaboration.
To cope with this responsibility incumbent on Universität Zürich, Carsten Schmitz, Krzysztof Nowak
and Linus Lindfeld permanently maintain a safe and efficient CIP2k operation for H1.
Shutdown repair: During the H1 maintenance shutdown in August 2004 we had the chance to
gain access the front-end electronics of the CIP2k chamber by removing the SpaCal calorimeter and
disconnecting the beam-pipe. Already before the shutdown the boards of the front-end electronics were
tested according to the procedure described in the last years SNF request and all defect boards could
be repaired or exchanged.
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The high duty cycle of the CIP2k system in the radiative environment leads to reoccuring deficiencies
so that we plan to access the CIP2k chamber once again in this years shutdown in December to repair
or replace a few dead channels.
Developments and maintenance: Although the trigger strategy, data aquisition and principle
operation of the CIP2k system is well established, the experience during continuous data taking has
shown that steady maintenance, and further developments and improvements of the trigger algorithms,
its simulations and the supervision of the system are necessary to meet the requirements of the running
experiment.
For example, all data quality checks were incorporated into the official data quality tools of H1 and
made accessible to all members of the collaboration. The instructions and online help manuals for
shift crews were updated, completed and transported to a self-maintaining wiki system. The PVSS
experiment controlling software (ECS) includes now further analysis features and is easier to use for
non-experts. Sophisticated and detailed Monte Carlo studies were performed to understand CIP2k
trigger decisions for various setups.
As the latest major improvement in the trigger strategy and data aquisition, the CIP2k L1 trigger
elements, track multiplicities and theta information are now sent to the Neural Network Trigger on
level 2 (L2). With this new feature, the efficiency for triggering Charged Current events on L2 is
expected to improve significantly. In addition, the CIP2k system is not only be used as a veto for
background processes, but contribute as a tracker to the analysis of low multiplicity events. Some
software development in this area are planned in near future.
Performance: As was already shown in previous reports, the CIP2k background reduction is efficient
and plays an important role in large parts of the L1 trigger decision. But also the performance as a
tracking device to study low multiplicity events has now become interesting. Figure 2.3 illustrates the
actual CIP2k chamber hit efficiency in each layer as the average in each phi sector over the detector
length in z for good tracks measured by the central trackers. The lower plot on the right shows that for
single track events the CIP2k trigger fills the central parts of the z-vertex histogram with an efficiency
of about 95% in healthy sectors. The depicted deficiencies in certain phi sectors can be deduced from
a combination of the decayed hit effciciencies in the individual layers. These inefficiencies are due to
irrecoverable high voltage degradations by three broken chamber wires as well as some newly broken
front-end electronics channels.
Plans: The successful repair during the last detector access advises us to repair during this year’s
access in December all front-end electronics that became unstable in the radiative environment. Improvements
of the stability are under discussion and being studied at the moment.
With continuous maintenance, watchful performance controlling and steady developments the CIP2k
system will also meet the requirements of the running H1 experiment in the future. As more and
more analyses of HERAII data are now performed, we are prepared for further requests by the H1
collaboration.
2.4.2 Analysis projects
2.4.2.1 Excited quarks
Models of composite quarks were introduced in an attempt to provide an explanation for the family
structure of the known quarks and for their pattern of masses. A natural consequence of these models is
the existence of excited states of quarks. Electron-proton interactions at very high energies provide an
excellent environment to look for excited quarks of the first generation. Jan Becker’s analysis extended
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efficiency
1.2
1
0.8
Layer 0, hit efficiency
efficiency
1.2
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0.8
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efficiency
1.2
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0.6
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0.4
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phi bin
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phi bin
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efficiency
1.2
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efficiency
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efficiency
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0 5 10 15 20 25 30
phi bin
Figure 2.3: The actual CIP2k chamber hit efficiency in each layer as the average in each phi
sector over the detector length in z for good tracks measured by the central trackers. Bottom
right: Single track CIP2k trigger efficiency in 32 phi sectors to reflect the 32 phi segments of
the chamber high voltage.
a previous analysis searching for excited fermions based on early H1 data. He used the 1999/2000 data
sets corresponding to a total luminosity of 63 pb −1 . No signal for an excited quark, decaying into a jet
and a photon was observed. The event selection criteria correspond to an efficiency of 40% to detect a
hypothetical excited quark signal. After these cuts 7 data events remained, which have to be compared
to 8.5 ± 3.0 events expected from standard model background. Mass dependant exclusion limits up to
275 GeV were derived.
Jan Becker’s thesis was accepted by our faculty in June 2005.
2.4.2.2 Prompt photon analysis in DIS and photoproduction
Isolated photons with high transverse momentum in the final state are a direct probe of the dynamics of
the hard subprocess, since they are directly observable without large corrections due to hadronisation
and fragmentation.
The observation and analysis of such photons has become a major focus of the analyses efforts of our
group. While Dr. Katharina Müller was contributing to the analysis of isolated prompt photons in the
photoproduction data in previous years, this activity has been extended to study high energy photons
produced in jets of deep inelastic scattering events. The so called photon fragmentation function
is an important ingredient to study the background to a light Higgs decaying into two photons at
LHC. In future we want to make use of our photon analysis experience by again working on prompt
photoproduction data in the HERA II data sample, including multi jet events, and to compare them
to QCD predictions.
Under the supervision of Dr. Katharina Müller two PhD students (Carsten Schmitz and Krzysztof
Nowak) contribute to this effort. An intense and productive collaboration with the institute of theoretical
physics of our university (Prof. Thomas Gehrmann, Dr. Aude Gehrmann, Eva Poulsen) for the
determination of the photon fragmentation function demonstrates the strong interest in this subject.
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Prompt photons are identified in the H1 liquid argon calorimeter (LAR) by a compact electromagnetic
cluster with no track pointing to it. The transverse energy is restricted to 3 GeV< E γ t < 10 GeV in
the pseudorapidity region −1 < η γ < 0.9. All the prompt photon analyses at HERA so far required
the photon to be isolated to supress background from neutral mesons [5] [7]. The requirement was
that the transverse energy in a cone of radius 1 (η − φ-plane) around the photon candidate is less than
10% of E γ T
. This rejects roughly 25% of the events with a resolved photon and leads to corrections
of the order of 20% from parton to hadron level which complicates the comparison to NLO calculations.
To ease the comparison with NLO calculations the isolation requirement is modified as follows. The
energy fraction z of the photon energy to the energy of the jet which contains the photon has to
be larger than 0.9. This infrared-safe definition of isolation also allows for measurements of photons
closer to jets and gives access to the quark-to-photon fragmentation function, which has not yet been
measured at HERA [8]. Figure2.4 shows the measured energy fraction z of the cluster energy to the
energy of the jet which contains the cluster compared to two monte carlo simulation (DJANGO and
RAPGAP). The excess of data in the highest z bin can be attributed to prompt photon events.
Jets
2500
AllJets, R0 = 1.0
2000
1500
1000
500
0
Data
DJANGO
RAPGAP
PROMPT PHOTONS
0.7 0.8 0.9 1 1.1
z
Figure 2.4: Energy fraction z of the cluster energy to the energy of the jet which contains the
cluster. Black dots are data, the two line histograms correspond to two monte carlo expectations
with no prompt photon production. The excess of data in the highest bin can be attributed to
prompt photon production, the shaded area gives its estimation from PYTHIA.
After selection of isolated photon candidates there is still a large fraction of background from neutral
mesons - mainly π 0 and η - in the event sample.
A new sophisticated method of identifying photons in the H1 detector has been elaborated during the
last year by Carsten Schmitz. It makes use of a set of estimators which fully exploit the different shapes
of photons and neutral mesons both transversly and longitudinally as well as their energy and angular
dependences. Figure2.5 shows the six estimators used for the analysis before any photon identification
or isolation cut. The shaded histogram shows the expected distribution for photons while the black
dots are data and the line histogram the simulated response for the neutral meson mix.
The estimators are combined in a likelihood analysis and a neural net analysis. The cluster shapes are
extracted from the simulation of single particles and fitted to the data. The fit yields the amount of
events with photons and neutral mesons. The fraction of neutral mesons (π 0 , η 0 , K 0 , ρ, Ω, K ⋆ etc)
is taken from monte carlo simulation (RAPGAP). Monte Carlo studies showed that neutral mesons
can well be separated from photons for transverse energies below 10 GeV. Only particles which decay
very asymmetrically are misidentified as photons. The new method of separating photons and neutral
mesons is used to measure the prompt photon cross section in deep inelastic scattering events, a
9

a) b) c)
Clusters
1000
800
600
400
200
DATA
DJANGO
SP Background - 10 Particles (sc. to DATA)
SP Photons (sc. to DATA)
Clusters
500
400
300
200
100
DATA
DJANGO
SP Background - 10 Particles (sc. to DATA)
SP Photons (sc. to DATA)
Clusters
800
700
600
500
400
300
200
100
DATA
DJANGO
SP Background - 10 Particles (sc. to DATA)
SP Photons (sc. to DATA)
0
0 0.5 1
EHotCore/ECluster
0
0 0.5 1
EHottestCell/ECluster
0
0 0.2 0.4
ELayer1/ECluster
Clusters
1800
1600
1400
1200
1000
800
600
400
200
DATA
DJANGO
SP Background - 10 Particles (sc. to DATA)
SP Photons (sc. to DATA)
0
0 10 20 30
Transverse Kurtosis
Clusters
1800
1600
1400
1200
1000
800
600
400
200
DATA
DJANGO
SP Background - 10 Particles (sc. to DATA)
SP Photons (sc. to DATA)
0
0 5 10 15 20 25
Transverse Radius
Clusters
900
800
700
600
500
400
300
200
100
0
DATA
DJANGO
SP Background - 10 Particles (sc. to DATA)
SP Photons (sc. to DATA)
0 0.5 1
d) e) f)
Symmetry
Figure 2.5: Estimators used for the photon meson discrimination before any photon identification
or isolation cut. The different estimators are energy fraction in a) the hot core of the
cluster, b) the hottest cell, c) first layer, d) shows the transverse kurtosis, e) the transverse
radius and f) the symmetry of the cluster. The black dots are data, the shaded histogram shows
the simulated distribution for photons, the red curve gives the background as estimated from 10
neutral mesons and the blue line gives the expectation from DJANGO Monte Carlo.
measurement which was not yet done in H1. Events are selected with a scattered electron in the
SPACAL and a photon candidate with a transverse energy larger than 3 GeV.
The prompt photon cross section in DIS will be measured as a function of Q 2 for Q 2 > 4GeV 2 . This
significantly extends the ZEUS measurement which started at Q 2 = 35GeV 2 [7]. Additionally the data
will be used to determine the photon parton distribution in the photon γ(x, Q 2 ) as proposed in [6].
A new analysis has just started on prompt photons in photoproduction (PhD thesis Krzysztof Nowak).
It will concentrate on the high statistics data of HERA-II and will make use of the sophisticated
photon identification described above. The aim is to measure the double differential prompt photon
cross section with sensitivity to the particle density functions both in the proton and the photon. The
analysis should focus on the analysis of the final state such as cross sections for photon plus multijets.
Furthermore it might be possible to reconstruct the intrinsic transverse momentum < k t > of the event
which was so far not possible with the available statistics.
It is planned to extend the analysis into the forward region of the detector a region which is also
of theoretical interest. This requires detailed investigations of the detector parts involved to get a
profound understanding of the conversion probability for the photon in forward region. The estimators
used for the photon identification need to be optimized to account for the higher energy of the photon
candidate and the better granularity of the calorimeter.
2.4.2.3 Isolated τ leptons in events with large missing p T
Since January 2005 Dr.Xella has been receiving a Marie-Heim-Vögtlin stipendium to restart her scientific
career after her maternity leave. The goal for the first year of this project is to finalize the current
work within the H1 experiment at HERA, and restart her previous activity within the International
10

Linear Collider (ILC) collaboration, in view of contributing to the ECFA/DESY workshop in Vienna
in November 2005.
Concerning the H1 activity, the analysis carried out by Dr.Xella involves the search for events with
isolated τ leptons and large missing transverse momentum. This analysis is of particular interest
to the H1 collaboration because previous searches for events with isolated electrons and muons have
detected a slight discrepancy (at the level of 2 σ) between the number of events observed and the
expected number from Standard Model (SM) processes (mainly Charged Current events and real W
boson production). This detection could be a possible hint for new physics beyond the SM. A possible
candidate for new physics could be single top production, which is extremely small at SM level, hence
not expected to be observable at HERA. This type of events have indeed a large missing momentum
(coming from the neutrinos involved in the process) and a isolated high pt τ lepton, coming from the
decay chain top → bottom W → bottom τ ν τ . The τ lepton final state, currently investigated by Dr.
Xella and collegues at DESY, is expected to have lower efficiency of detection, hence less discovery
potential with respect to the electron and muons final states, nonetheless it should be searched for, for
completeness of analysis, and should observe a cross section for events with isolated leptons compatible
with what observed in the other two channels.
The analysis is to be presented as ready for publication to the H1 collaboration in October 2005, and
a paper to be finalized shortly after this. The current final results show compatibility of the data
observed with the SM expectation, and a cross section upper limit well consistent with isolated leptons
of type electrons and muons. Figure 2.6 presents the most interesting variable, the total transverse
momentum of the hadronic system without the τ candidate. This variable, for high values, should be
mostly discriminating between events with heavy (bottom) quark content (single top) and low or no
flavour quark content (SM W production). As one can see, the observed data all lie at very low values
for this variable, hence no clear hint for new physics is observed.
Concerning the ILC activity, Dr.Xella has been attending a workshop in June 2005 at DESY, concentrating
on recent development in software for reconstruction and analysis within the ILC european
community. Occasionally during this year, when at DESY, she has been attending also meetings held
by and kept contact with the large ILC community at DESY. She is now planning soon to start studies
of light Higgs detection through the τ + τ − decay, which involves carefull understanding of how τ
identification depends on calorimeter and vertex detector design, and hence should provide interesting
input to the on-going detector design efforts.
Events
2
10
10
1
-1
10
-2
10
0 10 20 30 40 50 60 70 80 90 100
Ptx(Tau)
Figure 2.6: p T X of the events selected by the isolated high p T
τ analysis
11

2.4.2.4 Search for Lepton Flavor Violation
The search for lepton flavor violating (LFV) processes mediated by leptoquarks is the thesis project of
Linus Lindfeld.
In ep collisions, a LFV process can induce the appearence of a muon or tau instead of the electron in
the final state. A convenient concept to explain such exotic signatures is the exchange of a leptoquark.
Leptoquarks appear naturally as color triplet scalar and vector bosons in many extensions of the SM
such as Grand Unified Theories [10], Supersymmetry [11], Compositeness [12] and Technicolor [13]
allowing for LFV transitions like e → µ and e → τ.
After presenting the preliminary H1 result of the search for LFV processes in e + p-collisions at the
summer conferences ICHEP’04 (Beijing) and TAU’04 (Nara), the analysis was now extended to cover
also e − p-collisions. Analysing additional 13.5 pb −1 of e − p-data taken in 1998-1999 gives sensitivity to
F = 2 leptoquarks, where the fermion number F = |3B + L| is a combination of the baryon and lepton
number of the inital particles. As in the previously analysed e + p-data, no evidence for lepton flavor
violation could be found in e − p-data.
λ µq
=λ eq
1
-1
10
-2
10
Excluded at 95% C.L.
L
S 0
-
(e u)
R -
S 0
(e u)
R -
S ~ (e d)
L -
F=2 S 1
(e u,d)
-3
10
100 200 300 400 500 600
LQ
M / GeV
0
λ τq
=λ eq
1
-1
10
-2
10
Excluded at 95% C.L.
L
S 0
-
(e u)
R -
S 0
(e u)
R -
S ~ (e d)
L -
F=2 S 1
(e u,d)
-3
10
100 200 300 400 500 600
LQ
M / GeV
0
λ µq
1
R -
S 0
(e u) F=2
350 GeV
λ τq
1
R -
S 0
(e u) F=2
350 GeV
10
-1
250 GeV
10
-1
250 GeV
200 GeV
200 GeV
-2
10
10
-2
-1
10 1
λ eq
-2
10
10
-2
-1
10 1
λ eq
Figure 2.7: Top: Limits on the coupling constant strength λ lq = λ eq at 95% C.L. as a function
of the leptoquark mass for F=2 scalar leptoquarks decaying to a muon-quark pair (left) and
tau-quarks pair (right). Bottom: For three different masses limits at 95% C.L. on λ lq as a
function of λ eq in generic models where the LFV branching ratio BR = λ 2 lq/(λ 2 lq + λ 2 eq) is not
fixed.
Extending the Buchmüller-Rückl-Wyler effective model [14] to LFV processes, limits on the Yukawa
coupling of now all 14 leptoquark types to a muon or tau and a light quark were established. The
statistical analysis was completely revised and performed in analogy to the latest published H1 results
12

of a search for leptoquark bosons [15]. This statistical analysis follows a modified frequentist approach
and combines different search channels including all systematic uncertainties with correlations. Within
this new method, the search for LFV decays of leptoquarks into tau-quark pairs could be extended to
processes with a subsequent muonic decay of the tau lepton. Where this analysis follows that of the
search for LFV decays of leptoquarks into muon-quark pairs and improves the tau selection efficiency
significantly. Figure 2.7 shows limits on the Yukawa coupling of F=2 scalar leptoquarks to muonquark
pairs (left) and tau-quark pairs (right) as a representative example for the interpretation of the
analysis.
This analysis will be finalised for publication in the next months. The H1 collaboration plans to publish
the results as soon as possible in a dedicated paper. Linus Lindfeld plans to hand in his thesis in early
2006.
2.5 Research plan for 2005/2006
The analysis projects of our group desribed in the previous section will be continued.
All group members participate in the data taking, while the more senior people also take run coordination
responsibility during two week periods. Those residing in Hamburg are in addition responsible
for maintenance and data quality monitoring of the detector components built by our group (multiwire
proportional chamber and first level trigger).
The group contributes also to general trigger studies to determine new and more efficient combinations
of our trigger information with other detector systems of H1. For instance presently it is being studied
to extend the triggering of the hadronic energy of the events to smaller p T and higher pseudorapitity η
by feeding track pointing information from the Zürich vertex trigger to the second level neural network
tiggers of H1. Monte Carlo simulation studies are performed to estimate and optimise the physics
reach of such combinations. In addition the FPGA’s (field programmable gate arrays) of our trigger
have to be reprogrammed in order to cope with this and other requirements of the physics working
groups of H1.
With the upgrade activities accomplished and HERA-II data taking ending around 2007 no new hardware
projects are expected.
2.6 Schedule
The HERA collider will be shut down for maintenance and repair of components from November 2005
to January 2006. We will have the opportunity to repair a few dead electronic channels in our system
as well.
Then continous beam and data taking operation is planned until at least to summer 2007, when the
HERA collider will be shut down, in order to build the planned synchrotron radiation facility in the
Petra tunnel. Thereafter we still hope to be able to contribute to analysis projects for some years.
2.7 Relevance of proposed research
Until the start of the LHC, the HERA-collider will be the only operating high-energy complex in
Europe. As an ep collider it is also the unique tool to investigate proton structure and the interactions
and structure of the proton constituents down to dimensions of 10 −18 m. The recent upgrade has
strengthened the potential of this machine and that of the two experiments H1 and Zeus located at
HERA. The equipment built by the Zürich groups is an essential part of the H1-detector, essential for
all channels passing trigger and event selection, as well as for precision tracking. Members of our groups
13

have been spokesman, technical coordinator, trigger coordinator, software coordinators, polarisation
group coordinator, conveners of physics working groups and performed other central management
tasks.
The H1-collaboration has until 2005 published 140 papers, cited on average 57 times, with 20 in the
famous class (between 100 and 500 citations) and 31 in the well-known class (between 50 and 100
citations). Among the famous ones is already the publication which resulted from the thesis of R.
Wallny (Universität Zürich (2001) [16], 244 citations).
As is typical for a basic research instrument direct applications in industry apart from an occasional
patent are not of concern. However, for our graduate students, who are central to this effort, working
within the H1-collaboration has profound educational and professional merits, becoming familiar with
forefront technology which often has to be further developed. Finding employment inside and outside
the research community has never been a problem, some of our former students occupy management
positions in hightec companies or even founded their own.
14

2.8 Publications and talks of the group, and references
2.8.1 Articles
H1-Collaboration, A. Aktas et al., unless otherwise noted.
1. A General Search for New Phenomena in ep Scattering at HERA,
DESY 04 – 140, hep-ex/0408044, Phys. Lett.B602 (2004), 14 - 30.
2. Measurement of Prompt Photon Cross Sections in Photoproduction at HERA,
DESY 04 – 118, hep-ex/0407018, Eur. Phys. J. C38 (2005), 437 - 445.
3. Inclusive Production of D + , D 0 , D s + and D ∗+ Mesons in Deep Inelastic Scattering at HERA,
DESY 04 – 156, hep-ex/0408149, Eur. Phys. J. C38 (2005), 447 - 459.
4. A Direct Search for Magnetic Monopoles Produced in Positron-Proton Collisions at HERA,
DESY 04 – 240, hep-ex/0501039, Eur. Phys. J. C41 (2005), 133 - 141.
5. Measurement of Dijet Cross Sections for Events with a Leading Neutron in ep Interactions at
HERA,
DESY 04 – 247, hep-ex/0501074, Eur. Phys. J. C41 (2005), 273 - 286
6. Measurement of Beauty Production at HERA Using Events with Muons and Jets,
DESY 05 – 004, hep-ex/0502010, Eur. Phys. J. C41 (2005), 453 - 467
7. Measurement of Charm and Beauty Photoproduction at HERA D ∗ µ Correlations,
DESY 05 – 040, hep-ex/05003038, Phys. Lett. B621 (2005), 56 - 71.
8. Measurement of F2 c¯c and F2 b¯b at High Q 2 using the H1 Vertex Detector at HERA
DESY 04 – 209, hep-ex/0411046, Eur. Phys. J. C40 (2005), 349 -359
9. Search for Light Gravitinos in Events with Photons and Missing Transverse Momentum at HERA
DESY 04 – 227, hep-ex/0501030, Phys. Lett. B616 (2005), 31 -42
10. Measurement of Deeply Virtual Compton Scattering at HERA
DESY 05 – 065, hep-ex/0505061, Eur. Phys. J. C45 (2005), 1 - 11
2.8.2 Articles in print
11. Search for Leptoquark Bosons in ep Collisions at HERA
DESY 05 – 087, hep-ex/0506044, submitted to Phys. Lett. B (2005)
12. A Determination of Electroweak Parameters at HERA
DESY 05 – 093, hep-ex/0507080, submitted to Phys. Lett. B (2005)
13. Measurement of F2 cc and F2 bb at low Q 2 using the H1-vertex detector at HERA
DESY 05 – 110, hep-ex/0507081, submitted to Eur. Phys. J. C (2005)
14. Forward Jet-Production in Deep Inelstic Scattering at HERA
DESY 05 – 135, hep-ex/0508055, submitted to Eur. Phys. J. C (2005)
15. Elastic J/ψ-Production at HERA
DESY 05 – 161, to be submitted to Eur. Phys. J. C (2005)
15

2.8.3 Conference contributions, presented by group members
16. Charged and Neutral Current Cross Sections at HERA I and HERA II,
S. Schmitt, Proc. 32 nd Int. Conf. on High Energy Physics (ICHEP2004), Beijing (China),
August 16-22, 2004, ed. H. Chen et al., World Scientific (2005), p.
17. Tau Leptons at HERA, L. Lindfeld, Proc. 8th Int. Workshop on Tau Lepton Physics (Tau 04),
Nara, Japan, September 14 - 17, 2004, Nucl. Phys. Proc. Suppl. 144 (2005), 315 - 322.
18. Searches for Leptoquarks and for Lepton Flavor Violation withe the H1-Experiment,
L. Lindfeld, Proc. 13. Int. Workshop on Deep Inelastic Scattering, Madison, Wisconsin, USA,
April 27 - May 1, 2005, to be published.
2.8.4 Contributed papers to conferences
Contributed papers by the H1-Collaboration to EPS2005/HEP2005: Int. Europhysics Conf. on High
Energy Physics Lisbon (Portugal), July 21-27, 2005 and to LEPTON-PHOTON 2005, XXII. Int.
Symp. on Lepton-Photon Interactions at High-Energy, Uppsala, Sweden, June 30 - July 5, 2005. Only
those papers are listed, which have not yet been submitted to journals.
19. Measurement of the Polarisation Dependence of the Total e + p Charged Current Cross Section
(620,387)
20. Measurement of the Polarisation Dependence of the Total e − p Charged Current Cross Section
(621,388)
21. Measurement of the Inclusive DIS Cross Section at Low Q 2 and High x using Events with Initial
State Radiation (623,389)
22. Search for Events with τ-Leptons in ep Collisions at HERA (624,417)
23. Multi-jet Production in High Q 2 Neutral Current Deeply Inelastic Scattering at HERA and Determination
of α s (625,390)
24. Search for Doubly Charged Higgs Production at HERA (628,418)
25. Inclusive Jet Production in Deep Inelastic Scattering at High Q 2 at HERA (629)
26. Search for Lepton Flavor Violation in ep Collisions at HERA (630,419)
27. Measurement of Charm and Beauty Photoproduction at HERA using Inclusive Lifetime Tagging
(647)
28. Photoproduction of D ∗± Mesons Associated with a Jet at HERA (648,406)
29. The Charm Fragmentation Function in DIS (649,407)
30. The Structure of Charm Jets in DIS (650,408)
31. Study of Jet Shapes in Charm Photoproduction at HERA (651,409)
32. Dijets in Diffractive Photoproduction and Deep-Inelastic Scattering at HERA (634,396)
33. Multi-lepton events at HERA and a Generic Search for New Phenomena at Large Transverse
Momentum (635,420)
34. Diffractive D ∗ Meson Production in DIS at HERA (636,397)
35. Events with an Isolated Lepton and Missing Transverse Momentum at HERA (637,421)
36. Measurement of the Diffractive Cross Section in Charged Current Interactions at HERA (638,398)
37. Diffractive Photoproduction of ρ Mesons with Large Momentum Transfer at HERA (640,399)
38. Multiplicity Structure of Inclusive and Diffractive Deep-inelastic e + p Collisions at HERA (642)
39. Acceptance Corrected Ratios of D ∗ p(3100) and D ∗ Yields and Differential Cross Sections of
D ∗ p(3100) production (643,401)
40. H1 Search for a Narrow Baryonic Resonance Decaying to K 0 s p(¯p) (644,400)
41. Dijets in Photoproduction (680)
16

2.8.5 Theses
42. Excited Fermions,
Jan Becker, Thesis, Universität Zürich (2005)
References
[1] H1-Coll. V. Andreev et al., Phys. Lett. B 561 (2003) 241; hep-ex/0301030.
[2] General search for new phenomena in ep scattering at HERA, H1-Coll. A. Aktas et al., DESY
04-140, hep-ex/0408044, submitted to Phys. Lett. B
[3] H1-Coll. A. Aktas et al., Eur. Phys. J. C31 (2003) 17; hep-ex/0307015.
[4] H1-Coll. V. Aktas et al., Phys. Lett. B583 (2004) 28; hep-ex/0311015.
[5] H1 Collab. C. Adloff et al., A Search for Excited Fermions at HERA,
hep-ex/0407018, Eur. Phys. J. C17 (2000) 567.
[6] A.D. Martin, R.G. Roberts, W.J. Stirling, R.S. Thorne, Parton distributions incorporating QED
contributions,
hep-ph/0411040, Eur. Phys. J. C39 (2005) 155.
[7] ZEUS Collab. S. Chekanow et al., Observation of isolated high-E T photons in deep inelastic scattering,
hep-ex/0402019, Phys. Lett. B595 (2004) 86.
[8] [ALEPH Collaboration] D. Buskulic et al., First measurement of the quark to photon fragmentation
function, Z. Phys. C 69 (1996) 365.
[9] Physik-Institut der Universität Zürich, annual report 2004/5, chapter 3,
available at http://www.physik.unizh.ch/jb/2005/chap03.pdf.
[10] J.C. Pati and A. Salam, Phys. Rev. D 81 (1974) 275;
H. Georgi and S.L. Glashow, Phys. Rev. Lett. 32 (1974) 438;
P. Langacker, Phys. Rep. 72 (1981) 185.
[11] H.P. Nilles, Phys. Rep. 110 (1984) 1;
H.E. Haber and G.L. Kane, Phys. Rep. 117 (1985) 75.
[12] B. Schrempp and F. Schrempp, Phys. Lett. B 153 (1985) 101;
J. Wudka, Phys. Lett. B 167 (1986) 337.
[13] S. Dimopoulos and L. Susskind, Nucl. Phys. B 155 (1979) 237;
S. Dimopoulos, Nucl. Phys. B 168 (1980) 69;
E. Farhi and L. Susskind, Phys. Rev. D 20 (1979) 3404;
E. Farhi and L. Susskind, Phys. Rep. 74 (1981) 277.
[14] W. Buchmüller, R. Rückl and D. Wyler, Phys. Lett. B 191 (1987) 442.
[15] Search for Leptoquark Bosons in ep Collisions at HERA
H1-Coll. A. Aktas et al., DESY 05 – 087, hep-ex/0506044, submitted to Phys. Lett. B (2005)
[16] Deep-Inelastic Inclusive ep Scattering at Low x and a Determination of α s ,
H1-coll., C. Adloff et al., Eur. Phys. J. C21, 33 (2001)
17

2.9 H1 as an international collaboration
The H1-collaboration 1 works at the German research centre DESY (Deutsches Elektronen Synchrotron)
at the HERA electron protron storage ring (Hadron Elektron Ring Anlage), and consists of
the following institutions:
Armenia: Yerevan Physics Institute, Yerevan
Belgium: Inter-University Institute for High Energies ULB-VLB, Brussels
Physics Department, Universitaire Instelling Antwerpen, Wilrijk
Bulgaria Institute for Nuclear Research and Nuclear Energy, Sofia
Czech Republic: Institute of Physics, Academy of Sciences of the Czech Republic, Prague
Institute of Particle and Nuclear Physics, Charles Univ., Prague
France: DSM/DAPNIA, CEA-Saclay, Gif-sur-Yvette
CPPM, CNRS/IN2P3 - Univ Mediterranee, Marseille
LAL, Universite de Paris-Sud, Orsay
Laboratoire Louis Leprince Ringuet, LLR, IN2P3-CNRS, Palaiseau
Universites Paris VI et VII, LPNHE, IN2P3-CNRS, Paris
Germany: I. Physikalisches Institut der RWTH Aachen, Aachen
Exp. Physik 5, Univ. Dortmund, Dortmund
Deutsches Elektronen-Synchrotron, DESY, Hamburg
Institut f. Experimentalphysik, Univ. Hamburg, Hamburg
Max-Planck-Institut f. Kernphysik, Heidelberg
Kirchhoff-Institut für Physik, Univ. Heidelberg, Heidelberg
Physikalisches Institut, Univ. Heidelberg, Heidelberg
Institut f. Exp. u. Angew. Physik, Arbeitsgr. Hochenergiephysik, Kiel
Max-Planck-Institut f. Physik, Werner-Heisenberg-Institut, München
Fachbereich Physik, Bergische Univ., Wuppertal
Deutsches Elektronen-Synchrotron DESY, Zeuthen
Great Britain: School of Physics and Space Research, Univ. of Birmingham, Birmingham
Rutherford Appleton Laboratory, Chilton, Didcot
School of Physics and Chemistry, Lancaster University, Lancaster
Oliver Lodge Laboratory, University of Liverpool, Liverpool
Queen Mary and Westfield College, London
Physics Department, University of Manchester, Manchester
Italy: Dipartimento di Fisica Universita di Roma Tre and INFN Roma 3, Roma
Mexico Cinevestav-Merida, Departamento de Fisica Aplicada, 97310 Mérida, Yucatán;
Cinevestav-Zacateno, Departamento de Fisica, 07360 México, D.F.
Poland: The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Science, Cracow
Russia: Joint Institute of Nuclear Research JINR, Dubna
Institut f. Theoretical and Experimental Physics, ITEP, Moscow
P.N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow
Serbia and Montenegro: Faculty of Natural Sciences and Mathematics, University of Montenegro,
Podgorica
Slovakia: Inst. of Experimental Physics, Slowak Academy of Sciences, Kosice
Sweden: Physics Department, University of Lund, Lund
Switzerland: Paul-Scherrer-Institut, Villigen
Physik-Institut der Univ. Zürich, Zürich
Institut f. Teilchenphysik, ETH Zürich, Zürich
1 Homepage: http://www-h1.desy.de/h1/www/general/home/home.html
18

3 Research plan for LHCb
3.1 Status of CP-violation and the physics of B mesons
Forty years after its discovery in the CP-forbidden decay K 0 L → π+ π − , the study of CP violation has
developed into one of the most important and actively pursued fields of research in both theoretical
and experimental particle physics.
Within the Standard Model of particle physics, CP violation can be generated by a single phase in
the complex 3 × 3 Cabibbo-Kobayashi-Maskawa quark mixing matrix. The existence of CP violating
processes is required in order to generate a matter anti-matter asymmetry as it is observed in the
universe today. An improved understanding of the sources of CP violation therefore provides an
important link between particle physics and cosmology. Published measurements of CP violating
asymmetries in the decays of neutral Kaons and B mesons can be described consistently within the
Standard Model. However, the level of CP violation that is required to explain the observed matter
anti-matter asymmetry in the universe is several orders of magnitude larger than that predicted within
the Standard Model. This clearly hints at the need for additional sources of CP violation and therefore
for physics beyond the Standard Model.
Extentions to the Standard Model are required for reasons of theoretical consistency but, more importantly,
also in order to accomodate experimental evidence from measurements of basic cosmological
parameters. For instance, fluctuations of the microwave background radiation, the power spectrum
of large structures in the universe, the relative primordial abundance of light elements, and distance
measurements of very distant and faint supernovae consistently hint at the fact, that there must be
hitherto unknown dark matter and dark energy in the universe, with average energy densities that are
significantly higher than that of normal “baryonic” matter.
In B meson decays, the smallness of the relevant elements of the Cabibbo-Kobayashi-Maskawa quark
mixing matrix suppresses the standard tree level decay mechanisms, leading to a relatively large lifetime
of the B mesons. This suppression significantly increases the relative importance of processes
involving so called “penguin” or “box” diagrams, such that these become accessible to experimental
measurements at high statistics B experiments. Such diagrams including internal loops represent
a very sensitive system for indirect searches for deviations from the Standard Model and for “new
physics”. The rate of these processes, their CP asymmetry, and in some cases the energy asymmetries
of the decay products, are observables which could be influenced by effects of “new physics”, leading
to deviations of measured values from Standard Model predictions.
LHCb is a second-generation experiment that will perform precision studies of CP violating processes
in a large number of decay modes of B mesons, including very rare decays. The copious production
of all flavors of B mesons at the LHC, together with the unique particle-identification capabilities of
the LHCb detector, enable the experiment to investigate a wide range of decay channels that are not
accessible to existing experiments.
3.1.1 CP violation within the standard model
In the Standard Model, flavour-changing processes between quarks occur solely through charged-current
interactions, with couplings described by a 3 × 3 unitary matrix which is usually referred to as the
Cabibbo-Kobayashi-Maskawa (CKM) matrix [1, 2]:
⎛
V = ⎝ V ⎞
ud V us V ub
V cd V cs V cb
⎠ .
V td V ts V tb
The CKM matrix is fully described by four real parameters, three rotation angles and one complex
phase. It is this complex phase that generates CP violation in the Standard Model. A commonly
19

a) Im V ud V ∗ ub + V cd V ∗ cb + V td V ∗ tb = 0
b) Im V tb V ∗ ub + V ts V ∗ us + V td V ∗
ud = 0
η
η(1−λ 2 /2)
λ |V cb |
∗
(1−λ 2 /2)V ub
α
γ
0
ρ(1−λ 2 /2)
V td
λ |V cb |
β
1
Re
∗
V ub
λ |V cb |
ηλ 2 χ
0
ρ
(1−λ 2 /2+ρλ 2 )
γ−χ
(1−λ 2 /2)V td
λ |V cb |
V ts
|V cb |
Re
Figure 3.8: Two unitarity relations drawn in the complex plane.
used parametrization, introduced by Wolfenstein [3], uses the parameters λ, A, ρ and η.
parametrization, V is approximated as
⎛
1 − λ 2 /2 λ
⎞
Aλ 3 (ρ − iη)
V ≈ ⎝ −λ 1 − λ 2 /2 Aλ 2 ⎠ + δ V ,
Aλ 3 (1 − ρ − iη) −Aλ 2 1
In this
where
⎛
δ V = ⎝
0 0 0
−iA 2 λ 5 η 0 0
Aλ 5 (ρ + iη)/2 Aλ 4 (1/2 − ρ − iη) 0
CP violation occurs if η ≠ 0. The parameter λ is identical to the sine of the Cabibbo angle [1] and has
been measured to be 0.2229 ± 0.0022 in nuclear, Kaon and hyperon decays [4].
Of the nine unitarity relations of the CKM matrix, the following two are the most relevant for B physics:
⎞
⎠ .
V ud V ub ∗ + V cd V cb ∗ + V td V tb
∗
V tb V ub ∗ + V ts V us ∗ + V td V ud
∗
= 0
= 0
Using the parametrisation introduced above, these two relations can be drawn as triangles in the
complex plane as illustrated in Figure 3.8. Although the imaginary part of V cd plays an important role
for CP violation in K 0 K 0 oscillations, its contribution can be neglected in the first triangle. The second
triangle has a particular relevance to the B 0 s meson system. In the Wolfenstein parametrization,
arg V td = −β, arg V ub = −γ, arg V ts = χ + π ,
and all other elements of the CKM matrix are real.
The quantities |V cb | and |V ub | can be determined from various B meson decays generated by tree
diagrams. Furthermore, |V td | and |V ts | can be calculated from the B 0 dB 0 d
and B 0 0
s Bs
oscillation frequencies,
assuming that the oscillations proceed exclusively through the respective Standard Model box
diagrams shown in Figure 3.9. Currently, the B 0 dB 0 d
oscillation frequency is very well measured, but
only a lower limit has been set on the B 0 0
s Bs
oscillation frequency. Combined, all these measurements
determine two sides of the triangle shown in Figure 3.8a and therefore permit to construct the triangle
and extract the parameters A, ρ and η. The UTfit collaboration provides regular updates of Standard
Model analyses in the CKM framework and on derived limits on new physics [5].
3.1.2 Experimental results from B factories
The so-called “B factories” at SLAC (BaBar experiment) and KEK (BELLE experiment) have provided
us with a wealth of interesting data on B 0 d
meson decays. The most important result is certainly the
20

B 0 (B 0 )
s
b
d(s)
W
t c u
t c u
W
d(s)
b
B 0 (B 0 )
s
B 0 (B 0 )
s
b
d(s)
t c u
W
W
t c u
d(s)
b
B 0 (B 0 )
s
Figure 3.9: The Standard Model box diagrams that generate B d ; ¯B d and B s; ¯B s oscillations.
measurement of a CP asymmetry in the decay B 0 d → J/ψK0 S , which in the Standard Model proceeds
through a b→ ccs tree diagram. Under the two assumptions, that the decays are dominated by
the Standard Model processes and that only the Standard Model box diagrams shown in Figure 3.9
contribute to B 0 dB 0 d
oscillations, the time dependent CP asymmetry is related to the angle β of the
unitarity triangle. The latest result from Belle [6], using 386 Million BB events, is:
sin 2β = 0.652 ± 0.039 ± 0.020
This is about 10% lower than the average result from BaBar and Belle quoted a year ago. It also
represents a change of about one standard deviation with respect to the previous result from Belle,
which was based on a 2.5 times smaller number of BB events.
Both BaBar and Belle have reported [6] first results on the determination of the angle γ of the unitarity
triangle, using the Gronau-London-Wyler method which measures direct CP violation by observing
the rates of the processes B ± → DK ± . The process can occur directly through either external or (color
suppressed) internal tree diagrams. The neutral D meson is reconstructed by its decay D → K 0 S π+ π − .
The angle γ is extracted from the difference between the Dalitz analyses of the B + and B − processes.
Both experiments report a more than 2σ significant difference of the two processes and therefore direct
CP violation. The effect is observed also in the D ∗ K and in the DK ∗ final states. The present results
are
B ¯B pairs γ [2σ intervall]
BaBar 227 × 10 6 [12,137] ◦
Belle 275 × 10 6 [22,113] ◦
This determination of γ is believed to be “model independent”, since there are only tree diagrams
involved and these should not be affected by new physics.
Last year, the BaBar and Belle collaborations have also presented first results on the observation of
decays of the type b→ sss and b→ sdd . In the Standard Model, these decays proceed through penguin
diagrams, such as illustrated in Figure 3.10, and their CP asymmetries measure the same sin 2β as
it is measured in b→ ccs . Last year, a two standard deviation discrepancy between the two sin 2β
measurements had been reported.
New results with higher statistics, presented this summer, indicate that the discrepancy seems to have
decreased (see Figure 3.11). All rates except one are now within 1σ of the value of sin 2β measured in
b→ ccs (which itself came down by about 10%, see above). Nevertheless, all measurements involving
b→ s penguins still give consistently smaller values of sin 2β than expected. Since penguin and box
diagram are sensitive to new physics effects, both in rate and in CP-violation phases, such a discrepancy
would be of utmost importance, if it is confirmed by future measurements.
3.1.3 CP violation and physics beyond the Standard Model
With the increasing precision of experimental results, the success of the Standard Model CKM picture
in describing CP violation is impressive. The determination of the parameters of the unitarity triangle
21

Figure 3.10: The standard model penguin diagrams for the decay processes b→ sss and b→ sdd
.
using CP-conserving processes and that using CP-violating processes still give consistent results within
the current errors.
This success of the Standard Model turns into a puzzle if, as a possible solution to the gauge hierarchy
problem, it is considered to be an effective theory that is valid only up to energies not much above
the electroweak scale. This so called “flavour puzzle” admits two classes of possible solutions. Either,
models with flavour symmetry are invoked to explain the hierarchy of quark masses and mixing angles,
or minimal flavour violation models (MFV) are assumed where the only source of flavour violation is
in the Standard Model Yukawa couplings [5].
The most recent fits of Standard Model parameters and limits to new physics effects are presented in
[5]. The results clearly show that [7]
1. New Physics contributions in ∆B = 2 or ∆S = 2 can be up to 50%, but only if the new physics
has the same phase as the Standard Model. Otherwise, new physics can contribute at most 10%
to these processes.
2. In MFV models with low or moderate tan β, rare decays (such as B s → µµ or K 0 L → π0 νν) can
be enhanced only slightly compared to the Standard Model. However, a significant suppression
is also possible.
3. New sources of CP violation in s → d and b → d transitions are strongly constraint and unlikely.
In b → s, however, constraints from unitarity triangle fits are much less stringent and significant
effects due to new physics are well possible.
¿From the same fits, it can be shown that within the present experimental constraints a B 0 s oscillation
frequency with ∆m s > 38ps −1 would be a 5σ discovery of new physics. Also, any deviation from sin 2β
in b → s penguin decays would clearly be very important.
Another approach that is mentioned in [5] as being highly sensitive to effects of new physics, is the search
for an additional mixing phase φ Bs in the B 0 0
s Bs
system through the measurement of CP asymmetries
in the decays B 0 s → J/ψφ and B 0 s → D s K. These channels will be studied in detail with the experiment
LHCb.
There are many other examples of CP-violating decay modes for which the extracted values of the
phases of V td , V ub and V ts are affected differently by new physics. Precision studies of these decay
22

Figure 3.11: sin 2β as determined from time dependant CP violation analysis of some b → s
penguin decays [6]. The first line gives the present world average from tree decay b → c¯cs.
modes will permit a complementary insight into the properties of new physics, compared to direct
searches at ATLAS and CMS. Again, decays of B 0 s mesons play a crucial role. This gives a distinct
advantage to experiments at hadron machines over B factories operating at the Υ(4S) resonance.
Similarly, studies involving B c mesons and b baryons are also exclusive to experiments at hadron
machines.
3.1.4 LHCb: A second generation b-physics experiment
The LHCb experiment has been conceived to exploit the high b quark production cross section at the
LHC in order to study CP violation and other rare phenomena with highest possible precision and in a
wide range of B meson decays. The expected bb production cross section at the LHC is 500 µb, which
at the nominal LHCb luminosity of L = 2 × 10 32 cm −2 s −1 results in a production rate for b quarks
that is three orders of magnitude larger than at present-day e + e − colliders. Taking into account the
more difficult event selection and reconstruction at a hadron collider, detailed studies show that LHCb
will collect approximately the same number of reconstructed B 0 d
events in one year that the B factories
in total will have accumulated by the time when LHC will start producing data. In addition, LHCb
will for the first time permit to collect statistically significant samples of B 0 s and B c events.
Key requirements on the LHCb detector are a high reconstruction efficiency of the order of 95% for the
trajectories of charged particles, good π/K separation capability from a few GeV up to approximately
100 GeV, a very good proper time resolution of approximately 40 fs, and highly selective and efficient
23

triggers not only for decay channels involving leptons in the final state but also for purely hadronic
final states.
Figure 3.12: Side view of the LHCb detector. The LHC pp interaction region is located in the
centre of the LHCb Vertex Locator and defines the origin of the indicated coordinate system.
Since the b quark production at the LHC is strongly peaked towards small angles with respect to the
beam axis, the detector is layed out as a single-arm forward spectrometer. A side view of the detector
is shown in Figure 3.12. The Vertex Locator (VELO) will serve to reconstruct the primary interaction
vertex as well as secondary vertices from decays of neutral B mesons. The 4 Tm dipole magnet and
the four tracking stations (TT and T1-T3) will permit to reconstruct the trajectories and momenta of
charged particles. Two detector technologies are employed in the tracking system: the Silicon Tracker
is a silicon micro-strip detector that covers the entire acceptance of the TT station and the innermost
region of tracking stations T1-T3; the Outer Tracker is a straw drift-tube detector that covers the
outer regions of stations T1-T3. The RICH detectors (RICH1 and RICH2), the electromagnetic and
hadronic calorimeter systems (SPD, PS, ECAL and HCAL) and the five muon stations (M1-M5) will
be used for particle identification.
In the high-rate hadronic environment of the LHC, triggering is one of the major challenges for the
experiment. The LHCb trigger is designed to distinguish events containing B mesons from minimumbias
events through the existence of secondary vertices and the presence of particles with a large
transverse momentum (p T ).
The physics potential of the experiment for a selection of relevant decay channels has been documented
in a Technical Design Report [8].
3.2 Status of our own work
Members of the research group:
- Dr. Johannes Gassner, Dr. Frank Lehner, Dr. Matthew Needham, Stefan Steiner, Dr. Tariel
Sakhelashvili, Dr. Olaf Steinkamp, Prof. Dr. Ulrich Straumann
- Ph.D. students: Ralf Patrick Bernhard, Achim Vollhardt (graduated April 2005), Dmytro Volyanskyy,
Andreas Wenger.
The overall production schedule of the LHCb experiment foresees the completion of the detector by the
end of 2006, in order to be ready for physics data taking at the startup of the LHC, which is scheduled
24

Figure 3.13: Isometric view of the Trigger Tracker.
for 2007. The construction of the dipole magnet of the spectrometer has been finished. The magnet
has been operated up to its nominal currents, and a first measurement of the magnet field map has
been performed.
A significant fraction of the iron for the muon filters is in place. The electromagnetic calorimeter has
been fully assembled and the hadronic calorimeter is presently being installed. The RICH detectors
will follow and the outer and inner tracking stations, the TT station and the Vertex Detector will be
installed during the year 2006.
Our group at Universität Zürich concentrates on the development, construction, operation and data
reconstruction of the LHCb Silicon Tracker. The overall project management for the Silicon Tracker
lies within the responsibility of our group (O. Steinkamp and U. Straumann). In particular, our group
is responsible for the quality assurance of all silicon sensors, for the complete design and construction
of the TT station (Figure 3.13) and for the development and production of a digital optical readout
link for the Silicon Tracker.
The silicon sensors are currently being delivered in several batches by the company HPK. Upon arrival
in Zürich, the sensors are inspected visually, IV and CV curves are measured and relevant geometrical
parameters are verified on a precision metrology machine. The quality of the sensors that have been
so far delivered is excellent.
The production of the TT detector modules (“ladders”) has started. So far, 16 ladders comprising
seven silicon sensors each, have been produced. Based on the experience gained with the first produced
detectors, the construction procedure was improved in some aspects, and a different method of
connecting the bias voltage to the sensors was chosen.
In parallel to these construction activities, we work on software developments for track reconstruction,
databasing and experiment control operation.
We also perform Monte-Carlo simulation studies in preparation for physics analyses. Finally, one of us
contributes to the world-wide Monte Carlo event production effort, using the Swiss prototype of the
LHC computing farm located at the CSCS in Manno.
25

A detailed description of our activities and the status of our work is given in the following sections.
3.2.1 The Silicon Tracker project
The LHCb Silicon Tracker is a large-surface, wide-pitch silicon micro-strip detector that will be used
in the online triggering and in the offline reconstruction of charged-particle trajectories in the LHCb
spectrometer. The Silicon Tracker project consists of two sub-projects: The Trigger Tracker (TT) is
a 160 cm wide and 130 cm high tracking station located in between RICH1 and the dipole magnet of
the experiment. The Inner Tracker covers a cross-shaped, 120 cm wide and 40 cm high, region around
the beam pipe in tracking stations T1-T3 located downstream of the dipole magnet and in front of
RICH2. The total active surface of these silicon strip detector amounts to about 12 m 2 .
Our group has taken the full responsibility for the design and the production of the TT station. The
design and production of the Inner Tracker are with EPFL and University of Santiago de Compostela.
Front-end electronics are provided by the MPI Heidelberg, and power supply distributions for the readout
electronics and for the silicon detector bias are designed by University of Santiago de Compostela.
Finally, our group is responsible for the procurement and quality assessment of silicon sensors for both
detector parts and for the optical readout link for the detector.
3.2.2 Silicon sensors
The design of the silicon sensors for the Inner Tracker has been described in earlier reports [9]. Two
types of silicon sensors of different thickness but otherwise identical design will be employed. Extensive
tests of prototypes using particle beams at CERN and an infra-red laser setup in our laboratory have
been performed last year. The results are documented in [14] and show that sensors of 320 µm and
410 µm in thickness are expected to give sufficiently high signals for the single-sensor ladders and twosensor
long ladders employed in the Inner Tracker. The sensors for the IT detectors were ordered at
HPK Hamamatsu in fall 2004.
A pre-series of 60 sensors was delivered in January 2005, tested extensively in our laboratory and
successfully qualified. The results from these tests are documented in [11]. After releasing the series
production in April 2005, about 440 sensors have been delivered up to now and are presently undergoing
our quality assurance program. All sensors tested so far exhibit an excellent quality, with leakage
currents well below 1 µA at 500 V. We expect the remaining 80 sensors for the IT detector project to
be delivered by October 2005.
The design of the silicon ladders for the TT station will be described in the next section. The use
of long readout strips and Kapton interconnect cables makes it necessary to employ silicon sensors of
500 µm in thickness in order to obtain sufficiently high signal-to-noise ratios for full particle detection
efficiency and robust operation of the detector. A detailed study of possible detector layouts initiated
by Johannes Gassner has shown [15] that silicon sensors of the so-called OB2 type can be employed
here. These sensors were developed by the CMS collaboration and will be used in the outer barrel
of their silicon tracker. The CMS collaboration has very kindly allowed us to use their mask design
for the production of our sensors. Extensive measurements using an infra-red laser setup [16] and a
test-beam [17] have been carried out by our group and have demonstrated that, using these sensors,
an acceptable performance can be achieved for the long ladders foreseen for the TT station.
The use of CMS sensors has several advantages for us. Most importantly, we profit from the extensive
R&D studies that have been carried out by CMS. Moreover, HPK Hamamatsu agreed to deliver the
sensors to us for the same price that they apply for CMS. The contract with HPK Hamamatsu for a
total of 1000 sensors was placed in February 2005 and about 200 sensors have already been delivered
and tested. The remaining 800 sensors will be delivered to us by December 2005.
26

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ü@§’ü©ðâüm©¤¯ì¦ò^ì$’ò^ó7©þ¬¯ì¦ý𩥎aüÌ^ñû©§4dëd©)û§'üâ¯û
P¦¥¨§ 25@ FK;O?3;=

Figure 3.15: Basic detector unit for the TT station, consisting of seven sensors. Three sensors
are bonded together and their signals fed through the Kapton cable (blue) to the upper hybrid
(on the left side). The remaining four sensors are bonded together and connected to the lower
readout hybrid.
stability of the half-ladders will be provided by 1.0 mm wide and 5.5 mm high carbon fibre rails that
run along the long edges of the module.
Two detector modules will be joined together end-to-end in order to cover the full height of the
TT station. The mechanical connection between the two modules is achieved by gluing an additional
1 mm thick carbon fibre strip against the side-rails.
The Kapton interconnect cables were developed by Johannes Gassner, in close collaboration with the
company Dyconex in Bassersdorf (ZH). At the sensor end, they will be glued onto a thin G-10 support
plate that in turn will be glued onto the sensor. At the hybrid end, the cable will be glued onto
a pitch adaptor that connects to the hybrid. The cables consist of an approximately 100 µm thick
Kapton substrate that carries 512 copper traces on one side and a copper ground mesh on the other
side. In order to minimize the influence of the cable on the detector noise, it is mandatory to keep the
capacitance of the readout lines on the cable as small as possible. A beam test of a prototype ladder
consisting of three CMS-OB2 sensors and a 50 cm long prototype interconnect cable was carried out at
CERN in July 2004. Results from this beam test show that the expected signal to noise ratio is indeed
obtained (see Figure 3.16). The Kapton interconnect cables are presently produced at Dyconex and
will be delivered in October 2005.
In order to remove the heat generated by the front-end readout chips, the stack of hybrids will be
mounted onto an aluminium cooling balcony that also serves to assure the accurate positioning of the
ladder on a cooling plate that is integrated into the station frame described below. Cooling balconies
as well as cooling plates are already being produced in the mechanical workshop at our institute.
The assembly of the detector modules, including wire bonding, is presently carried out in our workshop.
An assembly room held in a dust-free environment has been set up for this purpose. A Delvotec
6400 automatic bonding machine and a pull tester have been purchased, funded by Universität Zürich.
Johannes Gassner, Tariel Shakelashvili and Peter Soland (presently all employed by Universität Zürich)
have been, or are being, trained to perform the wire bonding of the ladders.
Under the production management of Frank Lehner, a pilot production of several TT half-modules was
successfully launched in spring 2005. During this time a proof of principle of the module assembly could
be achieved and production steps were further refined. In the meantime, the production phase has
started and six TT half modules in the final design have already been produced. Our assembly schedule
28

Figure 3.16: Result from the test beam experiment in summer 2004, for a ladder consisting of
three CMS sensors and a 50 cm long Kapton signal cable. The measured signal to noise ratio
is shown as a function of the position of the particle between two strips. The parameter V fs
refers to the programmable pulse shape in our preamplifier (Beetle) chip; the standard value
has been used here.
foresees a continuous ramp up to full production speed until December 2005 and the production of all
148 half-modules by May 2005.
3.2.4 Module Testing
After production, all modules are tested in a “burn-in” stand set up by M. Needham together with
A. Vollhardt, D.Volyanskyy and A.Wenger. The tests permit to characterize the performance of the
modules and to locate potential problems. Since data is read out using the electronics chain that
will be used in the final experiment, the test-stand also acts as a full system test. Four TT modules
can be tested at a time in a custom-built box (Fig. 3.17). Each burn-in lasts around two days and
involves several temperature cycles between room temperature and 0 ◦ C. The test stand is equipped
with a laser system that allows to generate signals in the silicon bulk. LabView interfaces have been
developed to allow an automatic operation of the system. This allows, for example, module currents
and the temperature inside the box to be monitored and logged without the presence of an operator.
The behavior of the first produced modules as a function of time has been investigated over several
temperature cycles. Fig. 3.18 shows the stability of the current drawn by one of the ladders during the
time it was tested in the burn-in test stand.
The commissioning of the readout system and the development of related analysis software are ongoing.
Noise and pedestal data have been taken and are of good quality (Fig. 3.19). The Laser system will be
commissioned in the coming weeks. This will allow studies of pulse shapes and of the charge collection
as an function of bias voltage to be made.
3.2.5 Station mechanics
At the radiation level expected for the inner-most region of the Trigger Tracker [18], the silicon sensors
have to be operated at a temperature below 5 ◦ C in order to reduce radiation-damage induced leakage
currents to an acceptable level [19]. The operating temperature was chosen such that no significant
29

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ò¥’ð£8÷uñðâîý©â¯¥©R¯©©¡ðûÿ§¡ è§û ì§
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añû ¯ûÿ§¡ 2&U¤uûÿ§$e¯@üÕ¥Ž'/\@'§…¯ì’¥¤!
3.5e-07
3e-07
current
T
RH
30
25
Current (A)
2.5e-07
2e-07
1.5e-07
1e-07
5e-08
20
15
10
5
RH (%); T (C)
0
0
0 500 1000 1500 2000 2500 3000 3500
Time (min)
Figure 3.18: Sensor current as a function of time as measured in the burn-in test stand.
The three curves show (from top to bottom) temperature (right scale), current (left scale) and
relative humidity (right scale).
.û¦ ’ð A €£C’ðð'§äüâ^ñ¥û¦ÿûÿ/¢$¯'üâ¤þö©ð€ü'§ü©ðä¡€ & &1€ëÕì7üâ@§üâ©ð)¦ñü
deterioration of the signal-to-noise performance of the detector due to shot noise is expected to occur
over the full foreseen lifetime of the LHCb experiment.
ñ¤7¥ûÿ@§Ýò@©§©ûÿû©§ü
The mechanical design of the TT station has been developed by Stefan Steiner. The station comprises
four detection layers, where detector modules are installed vertically in the two outermost layers and
rotated under stereo angles of ±5 ◦ in the other two. As illustrated in Figure 3.13, all detector modules
are housed in a common light-tight and thermally insulating housing, that also provides electrical
insulation to the environment. Each module is mounted at both its ends onto one of two C-shaped
stainless-steel support frames. Since these support frames are located outside the acceptance of the
experiment, no special care has to be taken with regard to the radiation length of the selected materials.
Ladders within a detection layer are pairwise staggered in order to allow for a small overlap of the
sensitive surfaces of adjacent ladders and avoid acceptance gaps in between the ladders.
The two support frames are mounted onto precision rails that are fixed to a common support structure.
30

Figure 3.19: Raw and common mode noise corrected noise for TT4, 4 sensor sector.
The construction allows the two detector halves to be retracted from the beam pipe for detector
maintenance and during bake-out of the beam pipe. The frames include a cooling plate through which
liquid C 6 F 14 at -15 ◦ C will be circulated as cooling agent in order to remove the heat generated by the
front-end readout hybrids. Additional cooling ribs are integrated into the side walls of the support
frame in order to keep the ambient temperature inside the box at the desired value of 0 ◦ C. The detector
box will be continuously flushed with dry nitrogen in order to avoid condensation on the cold surfaces.
Thermal insulation to the environment is provided by 4 cm thick sheets of non-flammable polyetherimide
foam. In order to provide electrical insulation, these sheets are clad on both sides with 25 µm
thin aluminium foils and stiftened by 25 µm Kevlar tape. In the region around the beam pipe, the
thickness of the thermally insulating layer is reduced to approximately 3 mm in order to allow for the
silicon ladders to approach the beam pipe as close as possible.
The technical drawings for the station mechanics have been finalized by Stefan Steiner and details of
the mechanical interfaces to the LHCb support structures have been clarified. The box will be built
and fully assembled in our institute’s workshop during the next few months, and will be installed at
CERN in spring 2006.
3.2.6 Digital optical readout system for the LHCb Silicon Tracker
The digital optical readout system can be separated into a transmitting part close to the detector and
a receiving part in the counting house. The two are connected by optical fibers of up to 120 m in
length (see Figure 3.20). While the receiving part is not subjected to ionizing radiation and therefore
consists of common LHCb hardware, the expected radiation level close to the detector requiered the
development and qualification of a radiation-tolerant transmitting part.
So-called Service Boxes are located close to the detector but outside of the acceptance of the experiment.
A Service Box holds up to 16 Digitizer Boards and a single Control Card, which is designed at the
University of Santiago de Compostela. On each digitizer board, the analog data from one front-end
readout hybrid are received, digitized and encoded for subsequent transmission as optical signals via
fiber. All boards in a given Service Box are connected to each other via a custom designed backplane,
which holds linear voltage regulators in addition to the control signal distribution network.
As the readout hybrids for the Trigger Tracker and the Inner Tracker differ in the number of readout
chips they carry, two different versions of the digitizer board have been designed. A pre-production
of 17 boards of the TT version was produced in late 2004 and has been tested thoroughly. Some
minor errors were discovered and implemented in the IT version of the digitizer board, together with
additional circuit improvements that were proposed to improve the performance of some components
31

Figure 3.20: Schematic view of the digital optical readout system.
developed by the CERN micro-electronics group. A second pre-production (see Figure 3.21), consisting
of 10 boards, has been received in September 2005. Initial testing of these boards has indicated that
they are fully functional and that no further modifications will be required. An extensive test program
will be carried out before the design will be released for the mass production of ca. 350-400 boards for
each version.
In June 2005, as system-scale irradiation test of a digitizer board mounted onto a Service Box backplane
was performed at the Paul-Scherrer-Institute. The assembly was irradiated up to radiation levels of
four times the expected level at the foreseen location in the experiment. No failure or performance
degradation was observed.
The mechanical workshop of Universität Zürich has produced four prototype Service Boxes with 8
board slots each (see Figure 3.22). One of these was delivered, together with four digitizer boards,
to the EPF Lausanne where it is used in an IT module production test-stand. The remaining three
Service Boxes are used in the TT module production test-stand in Zürich.
A readout crate with common LHCb readout components (two TELL1 boards, a readout supervisor
and a small TTC network) has been set up to simulate the foreseen hardware environment of the
experiment as closely as possible. The TTC signal distribution was successfully integrated into the
DAQ of our teststand. Level-0 triggers and a master LHCclock signal could be sent to the Service Box
prototypes via optical fibers.
The CERN PVSS software environment has been installed and commissioned to permit controlling the
common LHCb Readout Supervisor.
The synchronous readout of up to 12 Beetle chips on three readout hybrids was demonstrated. The
hardware needed for a full upgrade to 64 Beetles on 16 hybrids is in place but needs still to be
commissioned to provide the full production test system.
32

Figure 3.21: Digitizer board for the Inner Tracker. The serialised analog signals from three
detector hybrids enter from the left. The 12 squared chips (8 on the bottom, 4 on the top)
are the ADC’s, one for each of the four outputs of every beetle. The connectors for the light
guides are clearly visible in red. The three larger squared chips close to the latter are the GOL
serialisers. The connector on the right delivers power, timing and ECS control both for these
cards and the hybrids connected to this card.
To inject signals into the silicon strip detectors of TT half-modules under test in the burn-in stand,
a fast (4ns) high power (30mW) laser pulse generator has been custom-developed by A.Vollhardt and
M.Suter (student). Its integration into the running DAQ is in progress.
For the next weeks, further integration work on the teststand readout system will be performed in
parallel to work on the final design of the Service Box backplane and the Service Box mechanics. After
a final verification of the performance of the Digitizer Boards, the designs are foreseen to be submitted
for production in late 2005. The turn-around time of about ten weeks will be used to set up a procedure
to test the boards as soon as they return from the assembly company.
The system will be installed and commissioned at CERN during the summer of 2006.
3.2.7 Detector simulation and track reconstruction software
Our group is also active in studies of the expected performance of the LHCb tracking system, in
preparation for the first data taking. Work is being undertaken by D. Volyanskyy and A. Wenger to
provide a detailed XML description of the TT station geometry that will be used in the LHCb Monte
Carlo and reconstruction programs (see Figure 3.23). Further work is required to tune parameters of
the detector simulation to fully reproduce results obtained in test-beams. In addition, M. Needham
is working on the definition of a new (and final) raw data format and the corresponding decoding
software. Compared to the previous definition of the data format, the new format reduces the raw
data size by about 25 %.
The group also actively pursues studies of track pattern recognition and fitting. M. Needham has
developed a fast and efficient algorithm for finding track seeds in the Inner Tracker [20]. This algorithm
is now being extended to include the Outer Tracker. A. Wenger has recently started to work on studies
to explore how the masses of the J/ψ and other resonances can be used to tune dE/dx corrections in
the track fit and understand the effect of the magnetic field, using real data.
3.2.8 Monte Carlo event production using the computing grid
One of our group members, Roland Bernet, acts as the Swiss representative in the LHCb national
computing committee and the LHCb representative in the Swiss national group for the LHC computing
33

Figure 3.22: Fully operational service box, used to read out the signals from the ladders in the
burn-in test stand (only partly visible on the right side). The analog signal input cables are
black. The timing signals are delivered optically (thin red cable) to the controller card on the
left side of the crate.
grid project. The latter is a subcomittee of the CHIPP and covers the experiments ATLAS and CMS
as well as LHCb.
Roland Bernet also acts as production manager of the LHCb Monte Carlo simulation, using the DIRAC
software developed by the LHCb collaboration. DIRAC (Distributed Infrastructure with Remote Agent
Control) has been developed to facilitate large scale simulation and user analysis tasks spread across
both grid and non-grid computing resources. It consists of a small set of distributed stateless Core
Services, which are centrally managed, and Agents which are managed by each computing site. DIRAC
utilizes concepts from existing distributed computing models to provide a lightweight, robust, and
flexible system. It uses parts of the LCG software. Roland Bernet also contributes significantly to the
debugging and comissioning of this software.
In the near future, we will concentrate on establishing an analysis infrastructure for LHCb, LHCb
Switzerland and LHCb Zürich, which is easy to use and hides as many of the daily GRID software
problems as possible. This includes implementing the knowledge of the Monte Carlo production team
into the analysis framework.
A Tier-2 center in the Swiss computing center CSCS in Manno is being set up. Roland acts as the
contact person of the LHCb collaboration to the CSCS and plays also a major role in running the
system and producing the required Monte Carlo samples for LHCb. In the last 12 months, about
1.8 Mio events have been produced in Zürich and Manno, using a total of more than 70’000 CPU
hours.
3.2.9 The event filter farm
The event filter farm is running the software trigger, which processes events accepted by the hardware
trigger Level-0. The nominal accept-rate of L0 is 1 MHz. The total processing power for this task
34

Figure 3.23: Layout of a stereo-layer in the TT detector XML.
has been estimated [21] to be approximately 1600 CPUs of the 2007 type (using ”Moore’s Law” for
extrapolation of CPU power from present days). This large installation has the typical size of a ”Tier-1”
center on the Grid.
The event filter farm is at the center of the data taking and online event selection and is thus very
important for all measurements, that will be done with LHCb. Our group is presently not directly
involved in the development of this farm, but the basic physics and technical concepts of Level-0 and
Level-1 triggering originate from the ideas of U. Straumann, when he acted as the trigger coordinator
until 1998. Since we ask the FORCE pool for funding to support this farm, we include here a short
discussion of how it will be constructed.
The farm barrack houses 50 racks, each of which can contain up to 44 standard 1 U servers, which
are equipped with 2 CPUs each. The farm can therefore consist of up to 2200 boxes or 4400 CPUs.
A special system, based on a horizontal airflow and water cooling, has been devised for the cooling of
these PCs.
The current trend in PC technology is to reduce the clock-frequency of the processors, but to increase
the number of processing units (”cores”) on the individual chips. This help to keep the power consumption
of individual nodes under control. Nevertheless, we have measured power consumptions of
up to 400 W when running the CPU at its full capacity. For this reason, and to increase reliability,
the computers in the event filter farm will be operated without harddisks. They will be booted and
operated via a dedicated Ethernet local area network.
A special control and monitoring system has been put in place, which integrates the supervision
and power management of all farm-PCs into the experiment wide Experiment Control System (using
PVSS). Many issues concerning the farm installation, such as cabling, booting, powering, control and
monitoring have been successfully tested in a “Real Time Trigger Challenge” that took place in 2005.
Currently, we are preparing the racks in the LHCb pit, a task which is foreseen to be finished by the
end of this year. The PCs themselves will be installed as late as possible to profit from continuously
falling prices.
3.2.10 Preparation for physics analyses
3.2.10.1 Data analysis of rare B s decays at Tevatron
The pp collider Tevatron at FERMILAB operates at a center of mass energy of about 2 TeV. Therefore,
the production rate of B mesons is significantly smaller than at the LHC, which will operate at a center
of mass energy of 14 TeV. Nevertheless, a sizeable number of B 0 s mesons has already been produced
35

at the Tevatron. The detection and analysis of their decays represents an excellent preparation for the
analysis of the data that will be produced by LHCb in future. As explained in section 3.1.3, the B 0 s
system is ideally suited for searches for new physics and possible solutions to the “flavour puzzle”.
Two members of our group (F. Lehner, R. Bernhard) have joined the D0 collaboration some time ago to
work on the silicon microstrip detector as well as on the analysis of B 0 s meson decays. The committee for
funding young reserach talents at Universität Zürich supports this activity with a significant financial
contribution.
Ralf Bernhard, as a PhD student under the supervision of Frank Lehner, has worked on the analysis
of the rare decay B 0 s → µµ. In his thesis (to be defended in October 2005) he presents searches for
rare B 0 s decays at √ s = 1.96 TeV, using a data sample of 300 pb − 1 integrated luminosity. The rare
decays B 0 s → µµ and B 0 s → µµφ are Flavour Changing Neutral Current decays, which are forbidden
at tree level in the Standard Model. However, they can proceed at very low rate through higher order
processes. The low rates predicted within the Standard Model place the observation of these decay
modes outside the reach of current studies, but several extensions to the Standard Model predict a
substantial enhancement of the branching fraction.
In the search for the decay B 0 s → µµ, four candidate events were observed (see Fig. 3.24), whilst a
background of 4.3±1.2 events was expected. In the absence of an apparent signal, a limit on the
)
2
Events/5 (MeV/c
1.8 2 Signal region
1.6
1.4
Sideband 1 Sideband 2
1.2
0.8 1
0.6
0.4
0.2
0
4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2
+
Invariant mass (µ
-
2
µ ) [GeV/c ]
Figure 3.24: The mass distribution after opening the box for the data sample. Four events
were found in the ±2σ region.
branching fraction B(B 0 s → µµ) was set. The resulting limit including all statistical and systematic
uncertainties at a 95% (90%) CL is
B(B 0 s → µµ) ≤ 3.7 × 10 −7 (3.0 × 10 −7 ).
In a combination with results from the CDF experiment the currently most stringent limits on the decay
modes B 0 s → µµ and B 0 d → µµ were obtained, excluding branching ratios of B(B0 s → µµ) > 1.5 · 10 −7
and B(B 0 d → µµ) > 4.0 · 10−8 at 95% CL.
Next, a search for the decay B 0 s → µµφ was performed. No candidate event was observed in the signal
region, whilst a background interpolation from signal side-bands predicted 1.6±0.4 events. Finding
no evidence for a signal, an upper limit on the branching fraction was set. Including the statistical
and systematic uncertainties, and using the central value of the world average branching ratio of
B 0 s → J/ψφ, the limit using a frequentist approach is:
B(B 0 s → µµφ) < 4.1 (3.2) × 10 −6
at 95% (90%) CL respectively.
magnitude.
This improves the best published limit from CDF by one order of
36

In addition to these searches for rare decays, also the decay mode B 0 s → ψ(2S)φ has been studied. An
observation with a significance of 5.99σ based on counting statistics has been obtained.
Finally, a first measurement of the ratio of the relative branching ratios
B(B 0 s → ψ(2S)φ)
B(B 0 s → J/ψφ)
and a measurement of the relative branching
B(B ± → ψ(2S)K ± )
B(B ± → J/ψK ± )
= 0.58 ± 0.24(stat) ± 0.09(sys)
= 0.60 ± 0.07(stat) ± 0.07(sys)
have been presented in this thesis. The obtained result for the B ± meson decay agrees well with previous
measurements and the result of the first measurement of the relative branching ratio of B 0 s → ψ(2S)φ
to B 0 s → J/ψφ agrees well with the expected value.
3.2.10.2 The process B 0 s → J/ψη ′
The B 0 s → J/ψη ′ decay can be used to measure the angle χ of the CKM unitarity triangle. The
angle can be extracted by a time dependent analysis of the CP asymmetry. Taking into account that
the angle χ can be predicted precisely and is expected to be very small in the Standard Model, this
measurement has a large discovery potential for new physics. Dmytro Volyanskyy is performing a
physics simulation study of the reconstruction of this decay channel with the LHCb detector. The
following goals have been achieved so far:
• An optimisation of selection cuts has been performed, using an “iterative method”. For the
chosen cuts, a background-to-signal ratio of less than 1.03 at 90% CL has been estimated. The
corresponding total efficiency and annual signal yield have been estimated to be 0.25% and 5.3k,
respectively.
• Invariant-mass, primary-vertex (PV) and secondary-vertex (SV) resolutions have been estimated
and are quoted in Table 3.2. The invariant mass distribution for the B 0 s is shown in Fig. 3.25.
Mass resolution, MeV σ(B s ) : 28.1 ± 0.9 σ(J/ψ) : 10.7 ± 0.3 σ(η ′ ) : 12.0 ± 0.4
PV resolution, µm σ x = 8.2 ± 0.3 σ y = 7.9 ± 0.3 σ z = 39.5 ± 1.6
SV resolution, µm σ x = 14.3 ± 0.5 σ y = 13.0 ± 0.4 σ z = 185 ± 8
Table 3.2: The mass, primary and secondary vertex resolutions for the B 0 s → J/ψη ′ .
• A proper time resolution of (34.8 ± 1.2) fs has been found. With this resolution, a precise
measurement of the time-dependent CP asymmetry in this decay mode should be possible.
• Specific background studies have been carried out to test the performance of the selection cuts
in suppressing events from b hadron decays with similar event topologies to that of the signal
decay.
• Using the trigger simulation of the L0 and L1 trigger decisions, a total trigger efficiency of 90.7%
has been estimated for reconstructed events from this decay.
• The momentum resolution and the reconstruction efficiency for tracks of charged particles from
the decay have been investigated as a function of momentum and direction.
During the next year, the study has to be continued to:
37

Figure 3.25: The invariant mass of B 0 s → J/ψη ′ , reconstructed using the decay modes J/ψ →
µ + µ − and η ′ → ρ 0 (π + π − )γ.
• Re-optimize the selection cuts using a ”Random Grid Search” method.
• Process more background Monte-Carlo events and obtain a more precise estimate of the backgroundto-signal
ratio.
• Perform a study of the sensitivity to the CP-violating parameters.
3.2.10.3 B c decays
It is expected that a large number of B c mesons will be produced at the LHC. Andreas Wenger has
performed a feasibility study in which he explored possibilities to make use of B c decays in LHCb. For
example, the angle γ pf the unitarity triangle could in principle be extracted in a model-independent
way using the strategy of reference triangles in decays to pairs of heavy hadrons [23, 22]. In addition,
some rare decays of the B c are considered to be promising for searches for new physics [25, 24]. However,
the study showed quickly that the expected rate of reconstructed events is too low and that it will not
be possible to perform sensitive measurements in a reasonable time.
The decay B c → J/ψ(µµ)π was looked at more closely. In this channel, the mass and the lifetime
of the B c meson should be measurable precisely. In order to understand the expected accuracy of
the measurement, correlations between the reconstructed mass and various kinematic variables were
studied.
38

3.3 Research plan for the forthcoming period
The entire TT station will be completely produced, assembled and tested in Zürich under the responsibility
of our group. Mass production of the ladders has started and will last until summer 2006.
The empty station should be installed at CERN in spring 2006. The ladders will be installed and
comissioned later, separately in small badges.
The readout link production is ongoing and expected to be finished until early 2006. Installation and
Comissioning of the whole detector system will happen in the second half of 2006.
In addition we will continue the physics analysis studies, in order to gain a better understanding of
the performance of the LHCb experiment and to be well prepared for the data analysis.
3.4 Manpower
We ask for support for the following persons:
1. Dr. Johannes Gassner joined our group as PostDoc in summer 2003, then employed by
Universität Zürich. He developed the Kapton interconnect cables used in the inner readout
sectors of the TT detector modules. He now works on the ladder commissioning and testing,
in particular he is acting as a “module doctor” whose task it is to understand and solve the
problems that occur on individual modules during the production. In close collaboration with
Stefan Steiner, Frank Lehner and Tariel Sakhelasvhili he also participates in the actual production
of the silicon ladders.
2. Dr. Jeroen van Tilburg will work as a PostDoc in our group and will be responsible for all
software aspects, including database, burn-in stand data analysis and silicon track reconstruction
in LHCb. He will also have to support us in the operation of the burn-in stand, as well as in the
comissioning of the ST system after installation at CERN.
3. Dmytro Volyanskyy is a student from our collaborating group in Kiev. He has worked as a
Ph.D. student in our group since November 2003 and concentrates on the quality assurance (burnin
station) for the TT module production. Complementing this technical work, he contributes to
the preparation of a physics analysis project within LHCb, looking at the detector performance
for the decay channel B 0 s → J/ψη’.
4. Andreas Wenger is a Ph.D. student working on the production, quality assurance and commissioning
of the Silicon Tracker detectors in LHCb. He studied the possibilities of LHCb to do
measurements of B c meson decay channels and contributes to the description of material distribution
and dE/dx features in the LHCb simulation program, as well as to alignment studies.
5. Stefan Steiner has worked as engineer in the physics institute of our university for many years,
employed by the SNF. His responsibilities include the selection of construction materials, the
development of detailed mechanical designs and the production of technical drawings, as well
as contributions to the actual mechanical construction and installation of the detectors of all
three particle physics groups at our institute (Truöl, Amsler, Straumann). He is also responsible
for the institute’s mechanical CAD system, CATIA, maintaining the system and training other
members of the institute in its use.
For the LHCb project, Stefan Steiner designed all mechanical parts of the detector modules and
the detector station.
In addition, Tariel Shakelashvili and Peter Soland, members of our institute, contribute to the ladder
production work. The physics students will continue to work on the sensor QA as required. Later
on, they could also participate in the burn-in measurements, if this turns out to be necessary. For all
mechanical work, we have the workshop of our institutes with its five technicians at our disposal at
least part time. Frank Lehner acts as the main TT production manager, while Olaf Steinkamp and
Ueli Straumann coordinate the silicon tracking project as a whole.
39

3.5 Investment plans
The overall Silicon Tracker project cost amounts to 5870 kCHF, of which Switzerland is supposed
to contribute 2508 kCHF. The remainder is shared between the other collaborators of the Silicon
Tracker group, namely MPI Heidelberg (Germany), University of Santiago de Compostela (Spain) and
Ukrainian Academy of Sciences Kiev (Ukraine). Most of this investment has been spent already.
As stated in the Memorandum of Understanding (MoU) [27], the total Swiss investment for the construction
of LHCb is expected to be 7.90 MCHF. This represents approximately 10.5% of the current
estimate for the total cost, 75.2 MCHF [28], which is essentially unchanged compared to that agreed
in the MoU. A fraction of about 28% of the total investments (which is fixed to be 2.25 MCHF for
Switzerland) is allocated to “common projects”, which will mainly contribute to the cost of the magnet,
CPU farm used for event filtering and reconstruction, and other large sub-systems or general infrastructure
of the experiment [27]. The remainder of the Swiss investment, 5.65 MCHF, is allocated to
the following specific sub-detector projects [27]: VErtex LOcator (VELO), Silicon Tracker, Trigger (i.e.
DAQ and CPU farm) and Data Handling (i.e. computing infrastructure, including the experimental
control system ECS).
Together, the two groups at EPFL and at the University of Zurich are aiming at fulfilling the Swiss
commitment for the LHCb construction cost. It was foreseen that the Lausanne and Zurich contributions
should roughly be 3/4 and 1/4 of the total Swiss investment. The exact share may be revised next
year, to adapt to the funding pattern imposed by our funding sources, including SNSF and FORCE. In
the mean time, the Lausanne and Zurich groups have planned to invest, by the end of 2006, 5.8 MCHF
and 1.9 MCHF respectively. This will cover most of the MoU cost, with the exception of 0.2 MCHF
which is left for investment in 2007.
The investment shares in the four different sub-detector items, as well as the needs for 2006, are given
in Table 3.3 for both Lausanne and Zurich. Lausanne and Zurich will devote an equal fraction of their
sub-detector investments to the common projects, determined such as to match the expected total
Swiss contribution. The corresponding needs for the common projects until the end of 2006 are given
in Table 3.4.
At the end of 2005, our projected investments will already have been funded for a total of 1.5 MCHF,
of which 0.3 MCHF have been allocated to the common projects and 1.2 MCHF to our specific subdetector
projects (see Table 3.3 for details). This includes contributions from Universität Zürich and
previous contributions from SNSF-FORCE. The currently missing investment funds until 2006 therefore
amount to 0.4 MCHF, In Lausanne, the total missing investment until 2006 is 1.1 MCHF. Altogether,
Switzerland still needs to invest 1.7 MCHF to meet the MoU expectation.
In addition to these investments for the detector construction, funds are needed for the Maintenance
and Operation (M&O). The general M&O costs, so-called “category A” costs, are determined on a
yearly basis at the level of the whole collaboration, and are covered by each country in proportion
to its number of PhD physicists and engineers. The Swiss share is currently 4.72%. Our expected
needs for the general M&O (cat. A) until 2009 are given in the first part of Table 3.5, based on the
current LHCb budget forecasts [29]. Starting in 2006, running costs for the sub-detectors under our
responsibility (ST, VELO) will have to be covered on top of these general M&O costs: these are called
“category B” costs, and the second part of Table 3.5 indicates the current best estimates.
Table 3.6 summarizes the needs for 2006 and 2007, both for Lausanne and Zurich. We ask FORCE to
cover in 2006 our planned contribution to the common projects, our share of the M&O cost (categories
A and B), and 0.5 MCHF to be invested in our sub-detectors. During this period, the remaining
investment and construction costs, about 0.2 MCHF, is expected to be covered by EPFL.
40

Already funded Needed Target by Fraction of
in years ≤2005 in 2006 end 2006 MoU target
Lausanne contributions
VELO 1988 154 2142 38%
Silicon Tracker (ST) 1193 82 1275 23%
Trigger + Data Handling (DAH) 327 423 750 13%
Sum of above 3508 659 4167 74%
Zurich contributions
Silicon Tracker (ST) 1205 28 1233 22%
Data handling (DAH) 0 126 126 2%
Sum of above 1205 154 1359 24%
Total Lausanne & Zurich 4713 813 5526 98%
Table 3.3: Swiss needs for the construction of the specific sub-detectors, in kCHF. The first
column of numbers includes projections until the end of 2005.
Already funded Needed Target by Fraction of
in years ≤2005 in 2006 end 2006 MoU target
Lausanne 1221 438 1659 74%
Zurich 298 243 541 24%
Total 1519 681 2200 98%
Table 3.4: Swiss needs, in kCHF, for the common projects.
Already funded Needed Needed Needed Needed
in years ≤2005 in 2006 in 2007 in 2008 in 2009
General Maintenance & Operation (M&O, category A)
Lausanne 93 39 67 65 65
Zurich 43 30 52 51 51
Total 136 69 120 116 116
Subdetector-specific Maintenance & Operation (M&O, category B)
Lausanne 0 49 133 145 158
Zurich 0 50 52 55 58
Total 0 99 185 200 216
Table 3.5: Swiss needs, in kCHF, for the Maintenance & Operation (M&O). The numbers
for category A are based on LHCb’s official budget forecast [29], while those for category B are
today’s best estimates assuming the VELO part is paid by Lausanne and the ST part is shared
equally between Lausanne and Zurich.
Lausanne Zurich Lausanne + Zurich
Year 2006 Year 2006 Year 2007
VELO, ST, Trigger, DAH 659 154 124
Common projects 438 243 50
M&O cat. A and B 88 80 305
Total needed 1185 477 479
Covered by EPFL 200
2006 request to SNSF 108
2006 request to FORCE 985 369
Table 3.6: Summary of the needs of the LHCb groups in Lausanne and Zurich for 2006 and
2007, and requests to FORCE for 2006, in kCHF. The sum of the first two lines of numbers
is equal to 1.7 MCHF and represents the investment still needed after 2005 to fulfill the MoU
commitment.
41

3.6 Publications of the Zürich group on LHCb and B physics
Articles
(1.4.2004 to 30.9.2005)
- A Combination of CDF and DØ Limits on the Branching Ratio of B 0 s → µ + µ − Decays.
R. Bernhard et al.: preprint hep-ex/0508058, August 2005
- A Search for the Flavor-Changing Neutral Current Decay B 0 s → µ + µ −
in p¯p Collisions at √ s = 1.96 TeV
V. M. Abazov et al, Phys. Rev. Lett. 94, 071802 (2005);
hep-ex/0410039; FERMILAB-Pub-04-215-E.
- The LHCb Silicon Tracker
B. Adeva et al, Nucl. Instr. and Meth. A546, (2005) 76-80
- Silicon Strip Detectors for the LHCb Experiment
O. Steinkamp, Nucl. Instr. and Meth. A541, (2005) 83-88
- Design of the LHCb Silicon Tracker
M. Agari and O. Steinkamp, Nucl. Instr. and Meth. A535, (2004) 352-356
- The LHCb Silicon Tracker
M. Needham, Nucl. Instr. and Meth. A530, (2004) 23-27
- LHCb Silicon Tracker Infrastructure
Y. Ermoline, Nucl. Instr. and Meth. A518, (2004) 309-312
PhD thesis
- An Optical Readout System for the LHCb Silicon Tracker
Achim Vollhardt, Dissertation, Physik-Institut, Universität Zürich, 2005
- Search for Rare Decays of the B 0 s Meson with the DØexperiment
Ralf Bernhard, Dissertation, Physik-Insitut, Universität Zürich, 2005
Conference contributions and invited talks
- Status of LHCb activities
O. Steinkamp, CHIPP plenary meeting, PSI, 28. Sept. 2005
- Hybrid Design, Status and Procurement for the LHCb Silicon Tracker
F. Lehner, Talk given at the 11th Workshop on Electronics for LHC and Future Experiments
LECC’05, September 12-16, 2005, Heidelberg, Germany, LHCb note: LHCb 2005-061
- Production of the LHCb Silicon Tracker Readout Electronics
A. Vollhardt, Talk at 11th Workshop on Electronics for LHC and future Experiments 12- 16 September
2005, Heidelberg, Germany, LHCb note: LHCb 2005-064
- Sensores de silicio para el Silicon Tracker del experimento LHCb
C. Lois, talk at the XXX Reunion Bienal de la Real Sociedad Espaola de Fisica, Ourense (Spain),
September 12-16, 2005.
- Status and expected performance of the LHCb tracking system
M. Needham, Talk presented at the 10 th International Conference on B physics at Hadron machines,
Assisi, June 20 th - 24 th 2005
42

- Sensor probing and radiation studies for the LHCb Silicon Tracker
C. Lois, talk at the 10th European Symposium on Semiconductor Detectors, Wildbad Kreuth,
Germany, June 12-16, 2005, LHCb Note: LHCb 2005-033 (conference proceedings submitted to
Nucl. Instr. and Meth. A)
- A radiation tolerant fiber-optic readout system for the LHCb Silicon Tracker
A. Vollhardt, Poster at 10th European Symposium on Semiconductor Detectors Wildbad Kreuth,
Germany, 12. Juni 2005, LHCb Note: LHCb 2005-032 (conference proceedings submitted to Nucl.
Instr. and Meth. A)
- Rare B decays at hadron colliders
F. Lehner, Talk given at the 20th International Workshop Weak Interactions and Neutrinos 2005
WIN’05, June 6-11, 2005, Delphi, Greece.
- Heavy Flavor Rare Decays at DØ
R Bernhard, Frontiers in Contemporary Physics III, 23-28 May 2005, Nashville, USA
- Search for rare flavor-changing and penguin decays of the B 0 s meson with the DØ detector
R Bernhard, APS Spring Meeting in Tampa, April 16-49, 2005.
- Status and prospects of the LHCb experiment
U. Straumann, Seminar given at Geneva University, 13. April 2005
- Search for rare B decays at the Tevatron with the D0 detector
R. Bernhard, invited talk to the Particle Physics Seminar, Indiana University 27.09.2004
- LHCb Silicon Tracker electronics: from R&D to Preproduction
Achim Vollhardt, 10th Workshop on Electronics for LHC and future Experiments, 13. - 17. September
2004, Boston, USA
- Search for rare B decays at the Tevatron
Ralf Bernhard, DPF 2004, UC Riverside, California, USA, Aug. 26 - 31, 2004
- Search for the rare decay B s → µµ with the D0 detector at the Tevatron
Ralf Bernhard, poster session, XXXII SLAC Summer Institute, Aug. 2 - 13, 2004
- Silicon Strip Detectors for the LHCb Experiment
O.Steinkamp, 5th International Symposium on the Development and Application of Semiconductor
Tracking Detectors, Hiroshima, June 14-17, 2004
- Search for flavor-violating decay B s → µµ
Ralf Bernhard, APS Spring Meeting in Denver, May 1-4, 2004
- Sensitivity analysis of the rare decay B s → µµ with the D0 detector
Ralf Bernhard, 2004 PHENOMENOLOGY SYMPOSIUM University of Wisconsin-Madison, April
26-28, 2004
Collaboration notes and technical reports
LHCb notes can be accessed through the CERN document server on http://cdsweb.cern.ch/
- Search for the Flavor-Changing Neutral Current Decay B s → µµ in pp collisions at √ s = 1.96 TeV
with the D0 Detector
D0 collaboration, D0 conference note 4514, 2. August 2004,
http://www-d0.fnal.gov/Run2Physics/WWW/results/B/B06/B06.pdf
43

- Observation of the Decay B 0 s → ψ(2S) φ and a Measurement of B(B 0 s → ψ(2S) φ)/B(B 0 s → J/ψ φ)
with the DØ detector
R. Bernhard and F. Lehner, DØ note 4869, July 2005.
- Search for the Rare Decay B 0 s → µ + µ − φ with the DØ Detector
R. Bernhard and F. Lehner, DØ note 4862, June 2005.
- Pre-Series Sensor Qualification for the Inner Tracker of LHCb
G.Baumann et al., LHCb-2005-037
- Sensitivity analysis for the rare decay B 0 s → µ + µ − φ with the DØ detector
R. Bernhard and F. Lehner, DØ note 4732, February 2005.
- Update of the upper limit for the rare decay B 0 s → µ + mu − with the DØ detector
R. Bernhard and F. Lehner, DØ note 4733, February 2005.
- Noise Considerations for the Beetle Amplifier Used With Long Silicon Strip Detectors
S. Köstner and U. Straumann, LHCb-2005-029
- Material Budget Calculation for the LHCb TT Station
M.Needham and A.Wenger, LHCb-2005-020
- Mechanical and Thermal Characterisation of a TT Half-Module Prototype
F.Lehner, C.Lois, M.Pangilinan and M.Siegler, LHCb-2005-007
- Updated Occupancies for the LHCb Silicon Tracker
M.Needham, LHCb-2005-006
- Laboratory Measurements on Irradiated Prototypes Ladders for the LHCb Inner Tracker
C.Lois et al., LHCb-2004-112
- The Mechanical Design of the LHCb Silicon Trigger Tracker
J.Gassner, F.Lehner and S.Steiner, LHCb-2004-110
- The Production, Assembly and Testing of the LHCb Silicon Trigger Tracker
F.Lehner et al., LHCb-2004-109
- Quality Assurance of 100 CMS2-OB2 Sensors
G.Baumann et al., LHCb-2004-105
- Measurements on Irradiated Silicon Sensor Prototypes for the Inner Tracker of LHCb
F.Lehner et al., LHCb-2004-104
- Measurements of a Prototype Ladder for the TT Station in a 120 GeV/c π - Beam
M.Agari et al., LHCb-2004-103
- Measurements of Prototype Ladders for the TT Station With a Laser
J.Gassner et al., LHCb-2004-102
- Grounding, Shielding and Power Distribution for the LHCb Silicon Tracking
C.Bauer et al., LHCb-2004-101
- The Silicon Tracker of the LHCb Experiment
Proceedings IEEE2004, Rome, Oct 17-19, 2004 S.Köstner et al., LHCb-2004-097
- The LHCb Silicon Tracker
H.Voss et al., LHCb-2004-077
- Tsa: Fast and Efficient Reconstruction for the Inner Tracker
M.Needham, LHCb-2004-075
44

- Prototype IF14-1 for an Optical 12-Input Receiver Board for the LHCb TELL1 Board
G.Haefeli, U.Uwer, A.Vollhardt and D.Wiedner, LHCb-2004-072
- Expected Particle Fluences and Performance of the LHCb Trigger Tracker
M.Siegler et al., LHCb-2004-070
- Silicon Strip Detectors for the LHCb Experiment
O.Steinkamp, Proceedings STD5, Hiroshima, Jun 14-17, 2004, LHCb-2004-054
- The LHCb Silicon Tracker Project
J.Blouw et al., LHCb-2004-051
- Raw Data Format and Readout Partitioning for the Silicon Tracker
M.Needham, O.Steinkamp, U.Straumann and A.Vollhardt, LHCb-2004-044
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46