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Scientific Report 2007-2009
Particle physics
The Physics Department of Sapienza University is involved in both ATLAS and CMS. A significant
fraction of the precision chambers of the ATLAS muon spectrometer (namely the external
part of the ATLAS apparatus aiming to detect and reconstruct the muons coming from the collisions)
have been assembled and tested in the Rome Physics Department [P1, P2]. Moreover
the logic of the muon trigger system, together with the electronics to realize it and the software
to operate it has been also partly prepared in Rome [P3]. The CMS Rome group has
been strongly involved in the project and realization of the electromagnetic calorimeter. This
is a very large detector based on PbWO 4 crystals aiming to identify and measure high energy
photons and electrons with excellent energy resolution [P6]. Both ATLAS and CMS groups
are now participating to data taking at CERN and to data analysis. In particular the ATLAS
group is involved in the Higgs search through its decay in four muons, in the study of Standard
Model processes like W and Z production and in the search for a class of the so called
“exotic” processes [P4]. The CMS Rome group is also involved in the search for the Higgs boson
decaying in a pair of photons, and in supersymmetric particles decaying also in photons and
electrons [P5]. Both searches are based on the performance of the electromagnetic calorimeter.
Two other groups from the Rome
Physics Department are involved in the
LHC experiments dedicated to more
specific items: LHCb and ALICE.
LHCb is designed to study flavour
physics by detecting rare decays of the
B mesons copiously produced in pp collisions
[P7]. ALICE aims to study possible
phase transitions in quantum fields
at very high energy densities, the so
called quark gluon plasma state of matter.
This study is possible by exploiting
the extremely large energy densities in
high energy interactions of heavy ions,
in particular Pb-Pb collisions [P8]. Both
Rome groups have participated in the
detector realization and commissioning.
Another group of the Department has
given an important contribution to the
realization of the physics program of
ZEUS, an experiment now completed at
DESY. This experiment has studied in
great detail the structure of the proton
in electron-proton collisions at the highest
energies ever reached [p22].
In all the activities presented here, a
key ingredient is the computing power.
For this reason we have set-up in Rome
a computer center, a so-called Tier2
[F3]. The INFN Roma Tier2 centre is
Figure 2: Top: one of the first 7 TeV collisions observed by CMS.
Bottom: the first event with two overlapping p-p collisions observed
by ATLAS. .
a shared facility among the ATLAS, CMS and VIRGO experiments. All the hosted resources are
fully integrated with the worldwide Grid Computing Infrastructure and participate to the INFN
and LCG/EGEE grids. At present a total of 1300 logical CPU cores and 500 TByte of storage
space are available. The ATLAS, CMS and VIRGO Tier2 sites have a very important role in their
respective experiments, for what concerns the Monte Carlo production and the user analysis. Each
Sapienza Università di Roma 103 Dipartimento di Fisica