Considering the Haystack: the pp Inelastic Cross ... - Physics Division
Considering the Haystack: the pp Inelastic Cross ... - Physics Division Considering the Haystack: the pp Inelastic Cross ... - Physics Division
Considering the Haystack: the pp Inelastic Cross Section at √s = 7 TeV with ATLAS Lauren Tompkins University of Chicago
- Page 2 and 3: The present • April 15th 2012, 25
- Page 4 and 5: Outline • Soft Physics at the Ene
- Page 6 and 7: LHC: The Energy Frontier ATLAS LBL
- Page 8 and 9: Theoretical Picture Minijet & multi
- Page 10 and 11: Outline • Soft Physics at the Ene
- Page 13 and 14: ATLAS Minimum Bias Trigger Scintill
- Page 15 and 16: ATLAS LBL RPM 05/22/2012 Forward Ca
- Page 17 and 18: Classifying pp Interactions Elastic
- Page 19 and 20: Diffractive Dissociation Double Dis
- Page 21 and 22: Monte Carlo Models of Particle Prod
- Page 23 and 24: The Measurement At least two MBTS h
- Page 25 and 26: Backgrounds (NBG) & Trigger (εtrig
- Page 27 and 28: Modeling Detector Response • Eval
- Page 29 and 30: Modeling Detector Response • Eval
- Page 31 and 32: Modeling Detector Material • Mate
- Page 33 and 34: Modeling Detector Material • Mate
- Page 35 and 36: Single-Sided Event Sample: NSS ev M
- Page 37 and 38: εsel and fξ
- Page 39 and 40: Summary of Systematic Uncertainties
- Page 41 and 42: Outline • Soft Physics at the Ene
- Page 43 and 44: Beam Separation Scans • Proposed
- Page 45 and 46: Luminosity Uncertainties • Calibr
- Page 47 and 48: Results • Calculate cross-section
- Page 49 and 50: Spring 2011 [mb] inel 100 80 60 40
- Page 51 and 52: 1 [mb] The Visible Cross Section X
<strong>Considering</strong> <strong>the</strong> <strong>Haystack</strong>: <strong>the</strong><br />
<strong>pp</strong> <strong>Inelastic</strong> <strong>Cross</strong> Section<br />
at<br />
√s = 7 TeV with ATLAS<br />
Lauren Tompkins<br />
University of Chicago
The present<br />
• April 15th 2012, 25 reconstructed vertices, Z➛
Revisiting <strong>the</strong> Past<br />
LBL RPM<br />
05/22/2012<br />
3
Outline<br />
• Soft <strong>Physics</strong> at <strong>the</strong> Energy Frontier<br />
• Overview of ATLAS and Relevant Subdetectors<br />
• Discussion of Diffractive Processes and Monte Carlo Models<br />
• The <strong>Inelastic</strong> <strong>pp</strong> <strong>Cross</strong>-Section Measurement<br />
• An Aside on Luminosity Measurements<br />
• Results<br />
• Connection to Cosmic Rays<br />
• Conclusions<br />
LBL RPM<br />
05/22/2012<br />
4
LHC: The Energy Frontier<br />
ATLAS<br />
LBL RPM<br />
05/22/2012<br />
• <strong>pp</strong> collider at √s = 7 TeV<br />
• Design lumi: 10 34 s -1 cm -2<br />
• Interaction rate: ~100 MHz<br />
• 2010 stats:<br />
• Initial lumi: 10 27 s -1 cm -2<br />
• Peak lumi: 10 32 s -1 cm -2<br />
• Interaction rate: ~1 MHz<br />
• Promises to shed light on<br />
<strong>the</strong> origins of electroweak<br />
symmetry breaking<br />
5
LHC: The Energy Frontier<br />
ATLAS<br />
LBL RPM<br />
05/22/2012<br />
<strong>Haystack</strong><br />
• <strong>pp</strong> collider at √s = 7 TeV<br />
• Design lumi: 10 34 s -1 cm -2<br />
• Interaction rate: ~100 MHz<br />
• 2010 stats:<br />
• Initial lumi: 10 27 s -1 cm -2<br />
• Peak lumi: 10 32 s -1 cm -2<br />
• Interaction rate: ~1 MHz<br />
• Promises to shed light on<br />
<strong>the</strong> origins of electroweak<br />
symmetry breaking<br />
Needle<br />
5
Why Measure <strong>the</strong> <strong>pp</strong> cross section?<br />
• High center-of-mass (s), low momentum transfer interactions<br />
are complex phenomena which QCD is currently unable to<br />
address<br />
• One of <strong>the</strong> most challenging open problems in strong interactions<br />
• Many basic unknowns:<br />
• What is <strong>the</strong> dependence of <strong>the</strong> interaction rate on s?<br />
• What is <strong>the</strong> division between color exchanging and color neutral<br />
interactions?<br />
• Start-up of LHC allows access to a<br />
new energy range to test models<br />
• Practically, measurement is useful<br />
for pile-up predictions for LHC<br />
high luminosity & energy running.<br />
LBL RPM<br />
05/22/2012<br />
6
Theoretical Picture<br />
Minijet &<br />
multi-parton<br />
interactions<br />
Soft Gluon<br />
Resummation<br />
AdS/CFT<br />
Correspondence<br />
Froissart-<br />
Martin Bound<br />
σtot,inel(s) ≤ ln 2 (s)<br />
LBL RPM<br />
05/22/2012<br />
Analytic<br />
Amplitudes<br />
Factorized Eikonal-<br />
Pomeron exchange<br />
Reggeon Field<br />
Theory<br />
7
The Total and Elastic <strong>Cross</strong> Sections<br />
• Total proton cross section<br />
is typically measured 2<br />
ways:<br />
• Forward elastic cross section at<br />
colliders (Optical Theorem)<br />
• Cosmic ray air showers<br />
• Specialized experiments/<br />
detectors exists at LHC<br />
for <strong>the</strong>se measurements<br />
• Totem<br />
• Alfa<br />
• Well-defined, direct measurements of σinel is an<br />
important complement to <strong>the</strong>se measurements<br />
[mb]<br />
tot<br />
<br />
LBL RPM<br />
05/22/2012<br />
160 <strong>pp</strong> Data<br />
<strong>pp</strong><br />
Data<br />
140<br />
120<br />
100<br />
80<br />
60<br />
40<br />
10<br />
ISR<br />
Data prior to 2011<br />
2<br />
10<br />
UA5<br />
Tevatron<br />
3<br />
10<br />
Cosmic Ray<br />
Data<br />
LHC<br />
4<br />
10<br />
s [GeV]<br />
8
Outline<br />
• Soft <strong>Physics</strong> at <strong>the</strong> Energy Frontier<br />
• Overview of ATLAS and Relevant Subdetectors<br />
• Discussion of Diffractive Processes and Monte Carlo Models<br />
• The <strong>Inelastic</strong> <strong>pp</strong> <strong>Cross</strong>-Section Measurement<br />
• An Aside on Luminosity Measurements<br />
• Results<br />
• Connection to Cosmic Rays<br />
• Conclusions<br />
LBL RPM<br />
05/22/2012<br />
9
ATLAS<br />
LBL RPM<br />
05/22/2012<br />
10
ATLAS<br />
Minimum Bias Trigger Scintillators:<br />
★2cm thick polystyrene scintillators read out by PMTs<br />
★Mounted on endcap calorimeter cryostat face plates (Z = 3.6 m)<br />
★Cover 2.09
ATLAS<br />
Inner Tracking Detector:<br />
★Silicon and transition radiation technologies<br />
★Coverage up to|η|< 2.5<br />
★Tracking for charged particle with pT > 100 MeV<br />
LBL RPM<br />
05/22/2012<br />
10
ATLAS<br />
LBL RPM<br />
05/22/2012<br />
Forward Calorimeters<br />
Inner Tracking Detector:<br />
★Liquid Argon and Co<strong>pp</strong>er/Steel absorbers<br />
★Coverage up to|η|< 4.9<br />
★Silicon and transition radiation technologies<br />
★Coverage up to|η|< 2.5<br />
★Tracking for charged particle with pT > 100 MeV<br />
10
Outline<br />
• Soft <strong>Physics</strong> at <strong>the</strong> Energy Frontier<br />
• Overview of ATLAS and Relevant Subdetectors<br />
• Discussion of Diffractive Processes and Monte Carlo Models<br />
• The <strong>Inelastic</strong> <strong>pp</strong> <strong>Cross</strong>-Section Measurement<br />
• An Aside on Luminosity Measurements<br />
• Results<br />
• Connection to Cosmic Rays<br />
• Conclusions<br />
LBL RPM<br />
05/22/2012<br />
11
Classifying <strong>pp</strong> Interactions<br />
Elastic<br />
Single Dissociation<br />
Central Diffraction<br />
• Elastic interactions: p+p→p+p (20% of σtot)<br />
• <strong>Inelastic</strong>: p+p→ something new (80% of σtot)<br />
• Predictions at 7 TeV vary between 65mb & 100mb for σinel<br />
• Color neutral processes make up 30% of σinel but are poorly<br />
understood<br />
LBL RPM<br />
05/22/2012<br />
Double Dissociation<br />
Non-diffractive Dissociation<br />
12
Single Dissociation<br />
Example of SD event<br />
No particles with<br />
-4.9
Diffractive Dissociation<br />
Double Dissociation<br />
}<br />
}<br />
X<br />
Y<br />
Single Dissociation<br />
• Color singlet exchange leads to<br />
rapidity gaps<br />
• Mass of dissociation product<br />
describes systems:<br />
= M 2 X /s<br />
• ξ relates to (pseudo)rapidity gap<br />
start, <strong>the</strong>refore detector acceptance:<br />
⌘min / log<br />
M 2<br />
X<br />
s<br />
LBL RPM<br />
05/22/2012<br />
} X<br />
Rapidity<br />
gap start<br />
14
Diffractive Models<br />
• Total detector acceptance<br />
depends on MX<br />
distribution near ξ cut<br />
• But we can’t measure MX!<br />
• Use a variety of models to assess<br />
dependence on MX distribution<br />
Measurement<br />
(MX > 15.7 GeV)<br />
arXiv:1005.3894<br />
LBL RPM<br />
05/22/2012<br />
• Consider many models for<br />
<strong>the</strong> diffractive mass<br />
distribution<br />
• Generators: Pythia, Phojet<br />
• 2 different fragmentation<br />
schemes (Pythia 6 vs Pythia 8)<br />
• Flat<br />
• Multiple variations of power law<br />
• Default model is<br />
Donnachie and Landshoff<br />
with ε = 0.085, α’= 0.25<br />
GeV -2 :<br />
d⇤SD<br />
/<br />
dM 2<br />
⇣ s<br />
M<br />
(t) =⇥ + 0 (t)<br />
⌘ 2 (t) 1 ✓<br />
1+<br />
◆ 2 M<br />
s<br />
15
Monte Carlo Models of Particle Production<br />
• Pythia 6: String<br />
fragmentation to produce<br />
particles for given MX<br />
• Pythia 8: Perturbative<br />
particle production using<br />
pomeron PDFs for MX ><br />
10 GeV<br />
• Default MC for this measurement<br />
• Multiple models for differential<br />
diffractive spectrum<br />
• Phojet: Dual Parton<br />
Model with cutoff to<br />
separate hard and soft<br />
diffractive processes<br />
LBL RPM<br />
05/22/2012<br />
16
Outline<br />
• Soft <strong>Physics</strong> at <strong>the</strong> Energy Frontier<br />
• Overview of ATLAS and Relevant Subdetectors<br />
• Discussion of Diffractive Processes and Monte Carlo Models<br />
• The <strong>Inelastic</strong> <strong>pp</strong> <strong>Cross</strong>-Section Measurement<br />
• An Aside on Luminosity Measurements<br />
• Results<br />
• Connection to Cosmic Rays<br />
• Conclusions<br />
LBL RPM<br />
05/22/2012<br />
17
The Measurement<br />
At least two MBTS hits Background and trigger<br />
efficiency measured in Data<br />
⇥( > 5 ⇥ 10 6 )=<br />
Limit measurement<br />
to detector<br />
acceptance<br />
(MX > 15.7 GeV)<br />
Dataset:1.2M events<br />
(2nd day of 7 TeV Stable LHC Beams)<br />
(N NBG)<br />
trig⇥ R Ldt ⇥ 1 f
Backgrounds (NBG) & Trigger (εtrig)<br />
• Beam gas and beam halo:<br />
• Measure with unpaired bunches :<br />
0.13% of total event sample<br />
• “Afterglow”: cavern radiation<br />
produced after a collision<br />
• Out-of-time afterglow measured by<br />
unpaired bunches<br />
• In-time afterglow measured from<br />
fractions of late hits in MBTS (0.4%)<br />
• Take 100% uncertainty on<br />
backgrounds:0.42%<br />
• Trigger is single MBTS trigger hit:<br />
• Measured with respect to offline<br />
selection to be 99.98% with an<br />
uncertainty of 0.09%<br />
LBL RPM<br />
05/22/2012<br />
19
Backgrounds (NBG) & Trigger (εtrig)<br />
• Beam gas and beam halo:<br />
• Measure with unpaired bunches :<br />
0.13% of total event sample<br />
• “Afterglow”: cavern radiation<br />
produced after a collision<br />
• Out-of-time afterglow measured by<br />
unpaired bunches<br />
• In-time afterglow measured from<br />
fractions of late hits in MBTS (0.4%)<br />
• Take 100% uncertainty on<br />
backgrounds:0.42%<br />
• Trigger is single MBTS trigger hit:<br />
• Measured with respect to offline<br />
selection to be 99.98% with an<br />
uncertainty of 0.09%<br />
LBL RPM<br />
05/22/2012<br />
Rate /Hz<br />
Rate /Hz<br />
10<br />
1<br />
0.48<br />
0.47<br />
0.46<br />
0.45<br />
0.44<br />
0.43<br />
0.42<br />
0.41<br />
0.4<br />
0.39<br />
0.38<br />
Afterglow<br />
ATLAS Preliminary<br />
Data 2010<br />
MBTS_C Triggers<br />
Unpaired<br />
bunches!<br />
0 500 1000 1500 2000 2500 3000 3500<br />
ATLAS Preliminary<br />
Data 2010<br />
Bunch Id<br />
MBTS_C Triggers<br />
800 1000 1200 1400 1600 1800 2000<br />
Bunch Id<br />
19
Backgrounds (NBG) & Trigger (εtrig)<br />
• Beam gas and beam halo:<br />
• Measure with unpaired bunches :<br />
0.13% of total event sample<br />
• “Afterglow”: cavern radiation<br />
produced after a collision<br />
• Out-of-time afterglow measured by<br />
unpaired bunches<br />
• In-time afterglow measured from<br />
fractions of late hits in MBTS (0.4%)<br />
• Take 100% uncertainty on<br />
backgrounds:0.42%<br />
• Trigger is single MBTS trigger hit:<br />
• Measured with respect to offline<br />
selection to be 99.98% with an<br />
uncertainty of 0.09%<br />
LBL RPM<br />
05/22/2012<br />
Rate /Hz<br />
Rate /Hz<br />
3<br />
10<br />
10<br />
2<br />
10<br />
1<br />
10<br />
0.48<br />
0.47<br />
0.46 10<br />
0.45<br />
0.44<br />
10<br />
0.43<br />
0.42<br />
0.41 10<br />
0.4<br />
Afterglow<br />
ATLAS Preliminary<br />
Paired<br />
Unpaired (Beam 1)<br />
MBTS_C Unpaired Triggers(Beam<br />
2)<br />
Data 2010<br />
Unpaired<br />
bunches!<br />
-100 0 -80 500-601000 -40 -20 1500 02000 20 2500 40 60 3000 80 3500 100<br />
3<br />
2<br />
CERN-THESIS-2011-046<br />
Ncounter<br />
Ncounters<br />
= 1<br />
CERN-THESIS-2011-046<br />
= 2<br />
Counter Time Bunch [ns] Id<br />
ATLAS Preliminary<br />
Paired<br />
Unpaired (Beam 1)<br />
MBTS_C Unpaired Triggers(Beam<br />
2)<br />
Data 2010<br />
0.39<br />
1<br />
0.38<br />
-100800 -80 -60 1000-401200 -20 1400 0 20 1600 40 601800 80 100 2000<br />
Counter Time Bunch [ns] Id<br />
19
Modeling Detector Response<br />
• Evaluated agreement of data and<br />
MC for MBTS counter response<br />
• Inner Counters: use calorimeters as tag<br />
• Outer Counters: use tracks as tag<br />
• Use track or calorimeter cell to tag<br />
counter, define efficiency as<br />
fraction of tagged counters with Q<br />
over threshold.<br />
• Correct for extrapolation error (track)<br />
and neutral component (calo)<br />
• Adjust MC threshold to match observed<br />
efficiency in data<br />
• Systematic taken as MC threshold<br />
which reproduces efficiency in<br />
“worst” data counter<br />
• Done separately for +/- (η) sides and<br />
Inner, Outer counters<br />
LBL RPM<br />
05/22/2012<br />
20
Modeling Detector Response<br />
• Evaluated agreement of data and<br />
MC for MBTS counter response<br />
• Inner Counters: use calorimeters as tag<br />
• Outer Counters: use tracks as tag<br />
• Use track or calorimeter cell to tag<br />
counter, define efficiency as<br />
fraction of tagged counters with Q<br />
over threshold.<br />
• Correct for extrapolation error (track)<br />
and neutral component (calo)<br />
• Adjust MC threshold to match observed<br />
efficiency in data<br />
• Systematic taken as MC threshold<br />
which reproduces efficiency in<br />
“worst” data counter<br />
• Done separately for +/- (η) sides and<br />
Inner, Outer counters<br />
LBL RPM<br />
05/22/2012<br />
Fraction of Tagged Counters<br />
0.03 Data 2010<br />
Pythia 6<br />
0.025<br />
Pythia 8<br />
Phojet<br />
0.02<br />
Pythia 6 + Ad. Material<br />
0.015<br />
0.01<br />
0.005<br />
0<br />
s = 7 TeV<br />
ATLAS Preliminary<br />
Track tagged counters<br />
0 1 2 3 4<br />
MBTS Counter Charge [pC]<br />
20
Modeling Detector Response<br />
• Evaluated agreement of data and<br />
MC for MBTS counter response<br />
• Inner Counters: use calorimeters as tag<br />
• Outer Counters: use tracks as tag<br />
• Use track or calorimeter cell to tag<br />
counter, define efficiency as<br />
fraction of tagged counters with Q<br />
over threshold.<br />
• Correct for extrapolation error (track)<br />
and neutral component (calo)<br />
• Adjust MC threshold to match observed<br />
efficiency in data<br />
• Systematic taken as MC threshold<br />
which reproduces efficiency in<br />
“worst” data counter<br />
• Done separately for +/- (η) sides and<br />
Inner, Outer counters<br />
LBL RPM<br />
05/22/2012<br />
Fraction of Tagged Counters<br />
0.03 Data 2010<br />
Pythia 6<br />
0.025<br />
Pythia 8<br />
Phojet<br />
0.02<br />
Pythia 6 + Ad. Material<br />
0.015<br />
0.01<br />
0.005<br />
0<br />
s = 7 TeV<br />
ATLAS Preliminary<br />
Track tagged counters<br />
0 1 2 3 4<br />
MBTS Counter Charge [pC]<br />
20
Modeling Detector Response<br />
• Evaluated agreement of data and<br />
MC for MBTS counter response<br />
• Inner Counters: use calorimeters as tag<br />
• Outer Counters: use tracks as tag<br />
• Use track or calorimeter cell to tag<br />
counter, define efficiency as<br />
fraction of tagged counters with Q<br />
over threshold.<br />
• Correct for extrapolation error (track)<br />
and neutral component (calo)<br />
• Adjust MC threshold to match observed<br />
efficiency in data<br />
• Systematic taken as MC threshold<br />
which reproduces efficiency in<br />
“worst” data counter<br />
• Done separately for +/- (η) sides and<br />
Inner, Outer counters<br />
LBL RPM<br />
05/22/2012<br />
Fraction of Tagged Counters<br />
0.03 Data 2010<br />
Pythia 6<br />
0.025<br />
Pythia 8<br />
Phojet<br />
0.02<br />
Pythia 6 + Ad. Material<br />
0.015<br />
0.01<br />
0.005<br />
Uncertainty on σ: 0.1%<br />
0<br />
s = 7 TeV<br />
ATLAS Preliminary<br />
Track tagged counters<br />
0 1 2 3 4<br />
MBTS Counter Charge [pC]<br />
20
Modeling Detector Material<br />
• Material increases efficiency/<br />
acceptance by increasing rate of<br />
conversions.<br />
• MBTS only “sees” charged particles<br />
• Exploit calorimeter’s sensitivity to<br />
neutral particles<br />
• Plot fraction of tagged counters seen as<br />
noise by <strong>the</strong> MBTS<br />
• Used a Pythia 6 sample reconstructed<br />
20% extra material in <strong>the</strong> pixel<br />
services to estimate material effects<br />
• Used twice difference (same as Pythia 6 -<br />
Data) as <strong>the</strong> systematic<br />
LBL RPM<br />
05/22/2012<br />
Fraction of Tagged Counters<br />
0.05<br />
0.04<br />
0.03<br />
0.02<br />
0.01<br />
0<br />
Data 2010<br />
Pythia 6<br />
Pythia 8<br />
Phojet<br />
Pythia 6 + Ad. Material<br />
ATLAS Preliminary<br />
FCAL tagged counters s = 7 TeV<br />
0 1 2 3 4<br />
Zero<br />
fraction<br />
MBTS Counter Charge [pC]<br />
Signal<br />
21
Modeling Detector Material<br />
• Material increases efficiency/<br />
acceptance by increasing rate of<br />
conversions.<br />
• MBTS only “sees” charged particles<br />
• Exploit calorimeter’s sensitivity to<br />
neutral particles<br />
• Plot fraction of tagged counters seen as<br />
noise by <strong>the</strong> MBTS<br />
• Used a Pythia 6 sample reconstructed<br />
20% extra material in <strong>the</strong> pixel<br />
services to estimate material effects<br />
• Used twice difference (same as Pythia 6 -<br />
Data) as <strong>the</strong> systematic<br />
Fraction of Tagged Counters<br />
zero<br />
f<br />
0.05<br />
0.04<br />
0.03<br />
0.02<br />
0.01<br />
0<br />
0.12<br />
0.1<br />
0.08<br />
0.06<br />
0.04<br />
0.02<br />
0 1 2 3 4<br />
Zero<br />
fraction<br />
s = 7 TeV<br />
ATLAS Preliminary<br />
Data 2010<br />
Pythia 6<br />
Pythia 8<br />
Phojet<br />
Pythia 6 + Ad. Material<br />
Data 2010<br />
Pythia 6<br />
Pythia 8<br />
Phojet<br />
Pythia 6 + Ad. Material<br />
ATLAS Preliminary<br />
FCAL tagged counters s = 7 TeV<br />
MBTS Counter Charge [pC]<br />
Signal<br />
FCAL tagged counters<br />
LBL RPM<br />
0<br />
0 1 2 3 4 5 6 7<br />
05/22/2012 MBTS Counter Number<br />
21
Modeling Detector Material<br />
• Material increases efficiency/<br />
acceptance by increasing rate of<br />
conversions.<br />
• MBTS only “sees” charged particles<br />
• Exploit calorimeter’s sensitivity to<br />
neutral particles<br />
• Plot fraction of tagged counters seen as<br />
noise by <strong>the</strong> MBTS<br />
• Used a Pythia 6 sample reconstructed<br />
20% extra material in <strong>the</strong> pixel<br />
services to estimate material effects<br />
• Used twice difference (same as Pythia 6 -<br />
Data) as <strong>the</strong> systematic<br />
Uncertainty on σ: 0.2%<br />
Fraction of Tagged Counters<br />
zero<br />
f<br />
0.05<br />
0.04<br />
0.03<br />
0.02<br />
0.01<br />
0<br />
0.12<br />
0.1<br />
0.08<br />
0.06<br />
0.04<br />
0.02<br />
0 1 2 3 4<br />
Zero<br />
fraction<br />
s = 7 TeV<br />
ATLAS Preliminary<br />
Data 2010<br />
Pythia 6<br />
Pythia 8<br />
Phojet<br />
Pythia 6 + Ad. Material<br />
Data 2010<br />
Pythia 6<br />
Pythia 8<br />
Phojet<br />
Pythia 6 + Ad. Material<br />
ATLAS Preliminary<br />
FCAL tagged counters s = 7 TeV<br />
MBTS Counter Charge [pC]<br />
Signal<br />
FCAL tagged counters<br />
LBL RPM<br />
0<br />
0 1 2 3 4 5 6 7<br />
05/22/2012 MBTS Counter Number<br />
21
Inclusive Event Sample: N<br />
ev<br />
MBTS<br />
counter<br />
dN<br />
• Used for cross-section<br />
measurement<br />
dN<br />
1<br />
Nev<br />
• Models span data for<br />
most of multiplicity<br />
range<br />
• Low Ncounter region most<br />
important for<br />
measurement<br />
0.2<br />
0.18<br />
0.16<br />
0.14<br />
0.12<br />
0.1<br />
0.08<br />
0.06<br />
0.04<br />
0.02<br />
0<br />
Inclusive<br />
s=<br />
7 TeV<br />
errors = stat ⊕ response<br />
⊕ material<br />
LBL RPM<br />
05/22/2012<br />
Data 2010<br />
Schuler-Sjostrand Pythia 6<br />
Schuler-Sjostrand Pythia 8<br />
Bruni and Ingelman<br />
DL =<br />
0.085, ’<br />
= 0.25 GeV<br />
DL =<br />
0.06, ’<br />
= 0.25 GeV<br />
-2<br />
DL =<br />
0.10, ’<br />
= 0.25 GeV<br />
Phojet<br />
5 10 15 20 25 30<br />
-2<br />
-2<br />
ATLAS<br />
MBTS<br />
Ncounter<br />
22
Single-Sided Event Sample: NSS<br />
ev<br />
MBTS<br />
counter<br />
dN<br />
dN<br />
ev<br />
1<br />
N<br />
• Sample of events with<br />
hits on one side of<br />
MBTS<br />
• Diffraction-dominated<br />
• Models give reasonable<br />
spread of uncertainty in<br />
diffractive contribution<br />
• Used to constrain<br />
contribution of<br />
diffractive events to<br />
inclusive event sample<br />
0.2<br />
0.18<br />
0.16<br />
0.14<br />
0.12<br />
0.1<br />
0.08<br />
0.06<br />
0.04<br />
0.02<br />
0<br />
Inclusive Single-sided<br />
s = 7 TeV<br />
2 5 4 106 15 8 1020 12 25 14 3016<br />
LBL RPM<br />
05/22/2012<br />
errors = stat ⊕ response<br />
⊕ material<br />
Data 2010<br />
Schuler-Sjostrand Pythia 6<br />
Schuler-Sjostrand Pythia 8<br />
Bruni and Ingelman<br />
DL <br />
= 0.085, <br />
’ = 0.25 GeV<br />
DL <br />
= 0.06, <br />
’ = 0.25 GeV<br />
DL <br />
= 0.10, <br />
’ = 0.25 GeV<br />
Phojet<br />
-2<br />
-2<br />
-2<br />
ATLAS<br />
N<br />
MBTS<br />
counter<br />
23
Relative Diffractive Contribution<br />
• Fractional contribution of<br />
diffractive process (fD) varies<br />
significantly between<br />
generators<br />
• Model dependent quantity<br />
• Constrain fD for each model<br />
by finding value which<br />
produces same ratio of<br />
single-sided to inclusive<br />
event sample (Rss) as data<br />
• Default model yields<br />
fD = 26.9 +2.5 -1.0 %<br />
ss<br />
R<br />
Rss(fD) = NSS<br />
0.16<br />
0.14<br />
0.12<br />
0.1<br />
0.08<br />
0.06<br />
0.04<br />
LBL RPM<br />
05/22/2012<br />
Ninc<br />
= ADSSfD + AND SS<br />
0.18 Data 2010<br />
Schuler-Sjostrand Pythia 6<br />
AD incfD + AND inc<br />
Schuler-Sjostrand Pythia 8<br />
Bruni and Ingelman<br />
DL = 0.085, ’<br />
= 0.25 GeV<br />
DL = 0.06, ’<br />
= 0.25 GeV<br />
-2<br />
DL = 0.10, ’<br />
= 0.25 GeV<br />
Phojet<br />
-2<br />
-2<br />
(1 fD)<br />
(1 fD)<br />
ATLAS<br />
s=<br />
7 TeV<br />
0.1 0.15 0.2 0.25 0.3 0.35 0.4<br />
fD<br />
24
εsel and fξ
MC Uncertainties on εsel and fξ
Summary of Systematic Uncertainties<br />
• Trigger: Difference between<br />
measurement with 2<br />
independent triggers<br />
• MBTS Response: Vary thresholds<br />
over full range of data<br />
efficiencies<br />
• Material: 40% uncertainty on<br />
material in |η|> 2.5.<br />
• Relative Diffractive<br />
Contribution: Vary fD within<br />
uncertainties<br />
•<br />
• Background: 100% uncertainty<br />
• MC Multiplicity: Difference<br />
between Pythia 8 and Pythia 6<br />
• ξ Distribution: largest difference<br />
between default and alternative<br />
models<br />
LBL RPM<br />
05/22/2012<br />
Source Uncertainty (%)<br />
Trigger E ciency 0.1<br />
MBTS Response 0.1<br />
Material 0.2<br />
fD<br />
0.3<br />
Beam Background 0.4<br />
MC Multiplicity 0.4<br />
distribution 0.4<br />
Luminosity 3.4<br />
Total 3.5<br />
27
Summary of Systematic Uncertainties<br />
• Trigger: Difference between<br />
measurement with 2<br />
independent triggers<br />
• MBTS Response: Vary thresholds<br />
over full range of data<br />
efficiencies<br />
• Material: 40% uncertainty on<br />
material in |η|> 2.5.<br />
• Relative Diffractive<br />
Contribution: Vary fD within<br />
uncertainties<br />
•<br />
• Background: 100% uncertainty<br />
• MC Multiplicity: Difference<br />
between Pythia 8 and Pythia 6<br />
• ξ Distribution: largest difference<br />
between default and alternative<br />
models<br />
LBL RPM<br />
05/22/2012<br />
Source Uncertainty (%)<br />
Trigger E ciency 0.1<br />
MBTS Response 0.1<br />
Material 0.2<br />
fD<br />
0.3<br />
Beam Background 0.4<br />
MC Multiplicity 0.4<br />
distribution 0.4<br />
Luminosity 3.4<br />
Total 3.5<br />
!!<br />
27
Outline<br />
• Soft <strong>Physics</strong> at <strong>the</strong> Energy Frontier<br />
• Overview of ATLAS and Relevant Subdetectors<br />
• Discussion of Diffractive Processes and Monte Carlo Models<br />
• The <strong>Inelastic</strong> <strong>pp</strong> <strong>Cross</strong>-Section Measurement<br />
• An Aside on Luminosity Measurements<br />
• Results<br />
• Connection to Cosmic Rays<br />
• Conclusions<br />
LBL RPM<br />
05/22/2012<br />
28
Luminosity Basics<br />
• Luminosity is a measure of <strong>the</strong> beam collision intensity:<br />
depends on Np/bunch, Nbunches, crossing frequency, &<br />
beam size.<br />
• Can be determined 2 ways:<br />
• Using a <strong>the</strong>oretically well known cross section and event counting:<br />
• From accelerator parameters:<br />
L· = Nev<br />
L = nbfrI1I2<br />
2⇡⌃x⌃y<br />
LBL RPM<br />
05/22/2012<br />
L = N1N2f<br />
Aeff<br />
((<br />
⌃x =( 2 1x + 2 2x) 1/2<br />
29
Beam Separation Scans<br />
• Proposed in 1968 by Simon van<br />
der Meer as a means of<br />
measuring beam sizes at <strong>the</strong> ISR.<br />
• Principle:<br />
• Measure <strong>the</strong> beam widths by scanning<br />
interaction rate as a function of beam<br />
separation<br />
• Can simultaneously measure visible crosssection,<br />
σvis<br />
• Then use σvis as calibration constant for<br />
future luminosity determination<br />
dN<br />
dt<br />
= nbfrI1I2<br />
2 x y<br />
vis<br />
LBL RPM<br />
05/22/2012<br />
Specific Rate R_sp [Hz]<br />
Data−fit<br />
<br />
1600<br />
1400<br />
1200<br />
1000<br />
800<br />
600<br />
400<br />
200<br />
0<br />
Peak Rate ~ L inst σvis<br />
ChPart = (58.4 ± 0.4) µ m<br />
ATLAS<br />
x<br />
Σx<br />
−2<br />
−4<br />
−300 −200 −100 0 100 200 300<br />
x<br />
[ µ m]<br />
024<br />
30
ATLAS Luminosity Detectors<br />
Track and Primary Vertex<br />
Event Counting<br />
BCM<br />
LUCID<br />
MBTS<br />
LBL RPM<br />
05/22/2012<br />
WLS fibers<br />
4+4 / 4+4<br />
16 Plastic<br />
Scintillators<br />
TAS<br />
EMEC<br />
HEC<br />
(front)<br />
HEC<br />
(back)<br />
FCal 1 FCal 2 FCal 3<br />
plug<br />
(EM) (Had) (Had)<br />
shielding<br />
Moderator shielding<br />
FCAL<br />
Pump<br />
ZDC<br />
140 m<br />
LAr Calorimeter<br />
237 m<br />
ZDC<br />
ALFA<br />
Primary Luminosity<br />
Measurement<br />
31
Luminosity Uncertainties<br />
• Calibration determined from 5 different scans in 2010<br />
• O(10) different methods/detectors used!<br />
• Uncertainty is dominated by knowledge of bunch charge (I1I2)<br />
• Already surpassed precision expected for beam scans!<br />
Scan Number I II–III IV–V<br />
Fill Number 1059 1089 1386<br />
Bunch charge product 5.6% 4.4% 3.1% Partially correlated<br />
Beam centering 2% 2% 0.04% Uncorrelated<br />
Emittance growth and<br />
o<strong>the</strong>r non-reproducibility 3% 3% 0.5% Uncorrelated<br />
Beam-position jitter – – 0.3% Uncorrelated<br />
Length scale calibration 2% 2% 0.3% Partially Correlated<br />
Absolute ID length scale 0.3% 0.3% 0.3% Correlated<br />
Fit model 1% 1% 0.2% Partially Correlated<br />
Transverse correlations 3% 2% 0.9% Partially Correlated<br />
µ dependence 2% 2% 0.5% Correlated<br />
Total 7.8% 6.8% 3.4%<br />
LBL RPM<br />
05/22/2012<br />
ATLAS-CONF-2011-011<br />
arXiv:1101.2185v1<br />
32
Outline<br />
• Soft <strong>Physics</strong> at <strong>the</strong> Energy Frontier<br />
• Overview of ATLAS and Relevant Subdetectors<br />
• Discussion of Diffractive Processes and Monte Carlo Models<br />
• The <strong>Inelastic</strong> <strong>pp</strong> <strong>Cross</strong>-Section Measurement<br />
• An Aside on Luminosity Measurements<br />
• Results<br />
• Connection to Cosmic Rays<br />
• Conclusions<br />
LBL RPM<br />
05/22/2012<br />
33
Results<br />
• Calculate cross-section using:<br />
• εsel = 98.8%,<br />
• εtrig = 99.8%,<br />
• fξ 5 ⇥ 10 6 )[mb]<br />
ATLAS Data 2010 60.33 ± 2.10(exp.)<br />
Schuler and Sjöstrand 66.4<br />
Phojet 74.2<br />
Ryskin et al. 51.8 56.2<br />
• Data are lower than MC generator predictions, higher than<br />
analytic calculation from Ryskin et. al.<br />
LBL RPM<br />
05/22/2012<br />
34
Extrapolating to σinel<br />
• To compare with previous measurements extrapolate<br />
using DL model (+15%)<br />
• O<strong>the</strong>r models range from 5 to 25%<br />
extrapolations<br />
• Take +/- 10% as extrapolation<br />
uncertainty<br />
⇥( >m 2 p/s) [mb]<br />
ATLAS Data 2010 69.4 ± 2.4(exp.) ± 6.9(extr.)<br />
Schuler and Sjöstrand 71.5<br />
Phojet 77.3<br />
Block and Halzen 69<br />
Ryskin et al. 65.2 67.1<br />
Gotsman et al. 68<br />
Achilli et al. 60 75<br />
LBL RPM<br />
05/22/2012<br />
Extrapolation<br />
• Data agree with most<br />
analytic calculations,<br />
lower than Phojet<br />
35
Spring 2011<br />
[mb]<br />
inel<br />
<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
1 10<br />
Data 2010 s = 7 TeV: > 5 x 10<br />
Schuler and Sjostrand:<br />
> 5 x 10<br />
PHOJET (Engel et al.): > 5 x 10<br />
Data 2010 s = 7 TeV: extrap. to > m<br />
Uncertainty (incl. extrapolation)<br />
Schuler and Sjostrand<br />
Block and Halzen 2011<br />
Achilli et al. (arXiv:1102.1949)<br />
<strong>pp</strong> Data<br />
<strong>pp</strong><br />
Data<br />
2<br />
Theoretical predictions and data are shown for > m /s unless specified o<strong>the</strong>rwise<br />
ATLAS data extrapolated using Pythia implementation of Donnachie-Landshoff model<br />
with = 0.085 for d/d<br />
10<br />
2<br />
LBL RPM<br />
05/22/2012<br />
p<br />
-6<br />
-6<br />
10<br />
-6<br />
3<br />
2<br />
p<br />
/s<br />
ATLAS<br />
4<br />
10<br />
s [GeV]<br />
• Presented <strong>the</strong> first measurement of inelastic cross-section<br />
• Data are lower than MC predictions, extrapolated value agrees with most<br />
analytic models<br />
36
Fall 2011<br />
• ALICE & CMS measured inelastic cross-section in<br />
limited phase space<br />
• Widely varying techniques with good agreement<br />
• TOTEM used 90m β* run to measure σtot, σinel and σel<br />
• Very precise measurement not subject to extrapolation uncertainties<br />
LBL RPM<br />
05/22/2012<br />
EPL 96 (2011) 21002<br />
37
1<br />
[mb]<br />
The Visible <strong>Cross</strong> Section<br />
X<br />
<br />
d<br />
d<br />
d<br />
X<br />
<br />
Cut<br />
75<br />
70<br />
65<br />
60<br />
55<br />
50<br />
45<br />
40<br />
10<br />
-8<br />
-7<br />
10<br />
-6<br />
10<br />
-1<br />
ATLAS<br />
s = 7 TeV<br />
ATLAS L = 7.1 µ b<br />
-1<br />
ATLAS L = 20 µ b<br />
-1<br />
TOTEM L = 1.7 µ b<br />
PYTHIA 6 ATLAS AMBT2B PYTHIA 8 4C<br />
PHOJET RMK<br />
-5<br />
10<br />
arXiv:1201.2808<br />
-4<br />
10<br />
10<br />
<br />
-3<br />
Cut<br />
LBL RPM<br />
05/22/2012<br />
• Atlas also measured<br />
cross section as a<br />
function of rapidity<br />
gap (ξ)<br />
• Comparison with<br />
with TOTEM shows<br />
models don’t predict<br />
correct dependence<br />
• Important for pile-up<br />
modeling!<br />
38
Outline<br />
• Soft <strong>Physics</strong> at <strong>the</strong> Energy Frontier<br />
• Overview of ATLAS and Relevant Subdetectors<br />
• Discussion of Diffractive Processes and Monte Carlo Models<br />
• The <strong>Inelastic</strong> <strong>pp</strong> <strong>Cross</strong>-Section Measurement<br />
• An Aside on Luminosity Measurements<br />
• Results<br />
• Connection to Cosmic Rays<br />
• Conclusions<br />
LBL RPM<br />
05/22/2012<br />
39
Connection to Cosmic Rays<br />
Blümer, Engel, Hörandel, arXiv:0904.0725<br />
LBL RPM<br />
05/22/2012<br />
• Shower MC used to<br />
determine primary<br />
CR energy up to<br />
GZK cut off<br />
• Big extrapolation!<br />
• LHC data useful to<br />
for:<br />
• Better p-air cross-section<br />
• Better shower modeling<br />
40
Constraining CR Models<br />
http://indico.cern.ch/getFile.py/access?contribId=21&sessionId=0&resId=0&materialId=slides&confId=140054<br />
LBL RPM<br />
05/22/2012<br />
41
Outline<br />
• Soft <strong>Physics</strong> at <strong>the</strong> Energy Frontier<br />
• Overview of ATLAS and Relevant Subdetectors<br />
• Discussion of Diffractive Processes and Monte Carlo Models<br />
• The <strong>Inelastic</strong> <strong>pp</strong> <strong>Cross</strong>-Section Measurement<br />
• An Aside on Luminosity Measurements<br />
• Results<br />
• Connection to Cosmic Rays<br />
• Conclusions<br />
LBL RPM<br />
05/22/2012<br />
42
Conclusions<br />
• Have made <strong>the</strong> first measurement of <strong>the</strong> proton-proton<br />
inelastic cross section at 7 TeV<br />
• Measurement made possible by <strong>the</strong> efficiency & simplicity of <strong>the</strong> MBTS<br />
detector and strength of <strong>the</strong> ATLAS detector to validate results<br />
• Current results are consistent with Froissart-Martin<br />
bound and agree with most analytic calculations<br />
• Already have generated interest in <strong>the</strong> Soft QCD/LHC<br />
community<br />
• Theory: collaborated with several <strong>the</strong>orists to obtain predictions at 7 TeV<br />
• Experiment: results from ALICE & CMS consistent with us, complimentary<br />
to TOTEM results<br />
• Extrapolation uncertainty on measurement will decrease<br />
as diffractive component is better understood<br />
LBL RPM<br />
05/22/2012<br />
43
References<br />
References<br />
[1] M. M. Block and F. Halzen, arXiv:1102.3163.<br />
[2] M. Ryskin, A. Martin, V. Khoze, arXiv:1102.2844, submitted to Eur. Phys.<br />
J. C.; private communication.<br />
[3] A. Achilli et al., CERN-PH-TH/2011-018, arXiv:1102.1949, submitted to<br />
JHEP.<br />
[4] R. Engel, Z. Phys. C 66 (1995) 203-214; R. Engel, J. Ranft, Phys. Rev.<br />
D 54 (1996) 4244-4262.<br />
[5] G. Schuler and T. Sjöstrand, Phys. Rev. D 49 (1994) 2257-2267.<br />
[6] P. Bruni and G. Ingelman, Phys. Lett. B311 (1993) 317.<br />
[7] A. Donnachie and P. V. Landsho , Nucl. Phys. B244 (1984) 322.<br />
[8] E. L. Berger et al., Nucl. Phys. B286 (1987) 704.<br />
[9] K. Streng, CERN-TH.4949 (1988)<br />
[10] E. Gotsman, E. Levin, U. Maor, J. S. Miller, Eur. Phys. J. C57 (2008)<br />
689-709; E. Gotsman, E. Levin, U. Maor, arXiv:1010.5323.<br />
LBL RPM<br />
05/22/2012<br />
44
Additional Slides
Why Measure <strong>the</strong> <strong>pp</strong> cross-<br />
“It used to be <strong>the</strong> case that when a new accelerator was initiated<br />
one of <strong>the</strong> first and most important experiments to be performed<br />
was <strong>the</strong> measurement of <strong>the</strong> total p-p cross section. Nowadays,<br />
this experiment is regarded with little interest, even though <strong>the</strong><br />
explanation of Regge behavior remains an interesting, unsolved<br />
and complicated problem for QCD.”<br />
-David Gross, 1998, 25th Anniversary of <strong>the</strong><br />
discovery of Asymptotic Freedom<br />
LBL RPM<br />
05/22/2012<br />
46
Creating a diffraction enhanced<br />
• Diffractive processes make<br />
MC tuning difficult<br />
• To study kinematics look at<br />
tracks in <strong>the</strong> single-sided<br />
event sample<br />
ATLAS-CONF-2010-048<br />
LBL RPM<br />
05/22/2012<br />
๏ For ICHEP used tracks<br />
with pT > 500 MeV<br />
๏ No detector corrections<br />
47
trk<br />
d N<br />
d<br />
Rapidity Gaps<br />
ev<br />
N 1<br />
Ratio(MC/Data)<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
1.2<br />
1.1<br />
1<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
ATLAS Preliminary<br />
s = 7 TeV<br />
Data<br />
Phojet<br />
Pythia8<br />
Pythia6<br />
Not corrected for detector effects<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5<br />
<br />
LBL RPM<br />
05/22/2012<br />
Δη<br />
MBTS MBTS<br />
• Δη = |ηMBTS - ηtrk| is sensitive to<br />
gap structure<br />
• Phojet shows best agreement<br />
• Favors dominantly SD contributions<br />
• Pythia 6 worst overall<br />
agreement, Pythia 8 favors high<br />
Δη<br />
48
trk<br />
d N<br />
d<br />
Rapidity Gaps<br />
ev<br />
N 1<br />
Ratio(MC/Data)<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
1.2<br />
1.1<br />
1<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
ATLAS Preliminary<br />
s = 7 TeV<br />
Data<br />
Phojet<br />
Pythia8<br />
Pythia6<br />
Not corrected for detector effects<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5<br />
<br />
LBL RPM<br />
05/22/2012<br />
Δη<br />
trk<br />
d N<br />
d<br />
1<br />
Nev<br />
MBTS MBTS<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
ATLAS Data<br />
Preliminary<br />
s = 7 TeV<br />
Phojet<br />
SD<br />
DD<br />
ND<br />
MC Sum<br />
Not corrected for detector effects<br />
0<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5<br />
• Δη = |ηMBTS - ηtrk| is sensitive to<br />
gap structure<br />
• Phojet shows best agreement<br />
• Favors dominantly SD contributions<br />
• Pythia 6 worst overall<br />
agreement, Pythia 8 favors high<br />
Δη<br />
ND<br />
SD<br />
DD<br />
<br />
48
trk<br />
d N<br />
d<br />
Rapidity Gaps<br />
ev<br />
N 1<br />
Ratio(MC/Data)<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
1.2<br />
1.1<br />
1<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
ATLAS Preliminary<br />
s = 7 TeV<br />
Data<br />
Phojet<br />
Pythia8<br />
Pythia6<br />
Not corrected for detector effects<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5<br />
<br />
LBL RPM<br />
05/22/2012<br />
Δη<br />
trk<br />
d N<br />
d<br />
1<br />
Nev<br />
MBTS MBTS<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
ATLAS Data<br />
Preliminary<br />
s = 7 TeV<br />
Phojet<br />
SD<br />
DD<br />
ND<br />
MC Sum<br />
Not corrected for detector effects<br />
0<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5<br />
• Δη = |ηMBTS - ηtrk| is sensitive to<br />
gap structure<br />
• Phojet shows best agreement<br />
• Favors dominantly SD contributions<br />
• Pythia 6 worst overall<br />
agreement, Pythia 8 favors high<br />
Δη<br />
ND<br />
SD<br />
DD<br />
<br />
48
trk<br />
d N<br />
d<br />
Rapidity Gaps<br />
ev<br />
N 1<br />
Ratio(MC/Data)<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
1.2<br />
1.1<br />
1<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
ATLAS Preliminary<br />
s = 7 TeV<br />
Data<br />
Phojet<br />
Pythia8<br />
Pythia6<br />
Not corrected for detector effects<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5<br />
<br />
LBL RPM<br />
05/22/2012<br />
Δη<br />
trk<br />
d N<br />
d<br />
1<br />
Nev<br />
MBTS MBTS<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
ATLAS Data<br />
Preliminary<br />
s = 7 TeV<br />
Phojet<br />
SD<br />
DD<br />
ND<br />
MC Sum<br />
Not corrected for detector effects<br />
0<br />
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5<br />
• Δη = |ηMBTS - ηtrk| is sensitive to<br />
gap structure<br />
• Phojet shows best agreement<br />
• Favors dominantly SD contributions<br />
• Pythia 6 worst overall<br />
agreement, Pythia 8 favors high<br />
Δη<br />
ND<br />
SD<br />
DD<br />
<br />
48
]<br />
-2<br />
[GeV<br />
trk<br />
N<br />
d p<br />
2<br />
d<br />
Ratio(MC/Data)<br />
pT Spectrum<br />
T<br />
<br />
d<br />
2 p<br />
1<br />
T<br />
ev<br />
N 1<br />
10<br />
10<br />
1<br />
-1<br />
-2<br />
-3<br />
10<br />
-4<br />
10<br />
-5<br />
10<br />
-6<br />
10<br />
1.5<br />
1<br />
0.5<br />
ATLAS Preliminary<br />
s = 7 TeV<br />
Not corrected for detector effects<br />
Data<br />
Phojet<br />
Pythia 8<br />
Pythia 6<br />
1 2 3 4 5 6<br />
p<br />
T<br />
[GeV]<br />
• Phojet shows best agreement<br />
over full pT range<br />
• Pythia 8 overestimates at low pT<br />
• Pythia 6 underestimates for most pT<br />
• Pythia 6 diffractive component<br />
very soft<br />
LBL RPM<br />
05/22/2012<br />
• Agrees fairly well in high pT tail where<br />
ND component dominates<br />
49
]<br />
-2<br />
[GeV<br />
trk<br />
N<br />
d p<br />
2<br />
d<br />
Ratio(MC/Data)<br />
pT Spectrum<br />
T<br />
<br />
d<br />
2 p<br />
1<br />
T<br />
ev<br />
N 1<br />
10<br />
10<br />
1<br />
-1<br />
-2<br />
-3<br />
10<br />
-4<br />
10<br />
-5<br />
10<br />
-6<br />
10<br />
1.5<br />
1<br />
0.5<br />
ATLAS Preliminary<br />
s = 7 TeV<br />
Not corrected for detector effects<br />
Data<br />
Phojet<br />
Pythia 8<br />
Pythia 6<br />
1 2 3 4 5 6<br />
p<br />
T<br />
[GeV]<br />
LBL RPM<br />
05/22/2012<br />
]<br />
-2<br />
[GeV<br />
trk<br />
n<br />
2<br />
d<br />
p<br />
d<br />
<br />
d<br />
2 p<br />
1<br />
T<br />
T<br />
ev<br />
N 1<br />
10<br />
10<br />
10<br />
1<br />
-1<br />
-2<br />
-3<br />
10<br />
-4<br />
10<br />
-5<br />
10<br />
-6<br />
10<br />
Preliminary<br />
s = 7 TeV<br />
Pythia 6<br />
ATLAS Data<br />
Pythia 6<br />
Not corrected for detector effects<br />
MC Sum<br />
ND<br />
SD<br />
DD<br />
SD ND<br />
DD<br />
1 2 3 4 5 6<br />
p<br />
T<br />
[GeV]<br />
• Phojet shows best agreement<br />
over full pT range<br />
• Pythia 8 overestimates at low pT<br />
• Pythia 6 underestimates for most pT<br />
• Pythia 6 diffractive component<br />
very soft<br />
• Agrees fairly well in high pT tail where<br />
ND component dominates<br />
49
]<br />
-2<br />
[GeV<br />
trk<br />
N<br />
d p<br />
2<br />
d<br />
Ratio(MC/Data)<br />
pT Spectrum<br />
T<br />
<br />
d<br />
2 p<br />
1<br />
T<br />
ev<br />
N 1<br />
10<br />
10<br />
1<br />
-1<br />
-2<br />
-3<br />
10<br />
-4<br />
10<br />
-5<br />
10<br />
-6<br />
10<br />
1.5<br />
1<br />
0.5<br />
ATLAS Preliminary<br />
s = 7 TeV<br />
Not corrected for detector effects<br />
Data<br />
Phojet<br />
Pythia 8<br />
Pythia 6<br />
1 2 3 4 5 6<br />
p<br />
T<br />
[GeV]<br />
LBL RPM<br />
05/22/2012<br />
]<br />
-2<br />
[GeV<br />
trk<br />
n<br />
2<br />
d<br />
p<br />
d<br />
<br />
d<br />
2 p<br />
1<br />
T<br />
T<br />
ev<br />
N 1<br />
10<br />
10<br />
10<br />
1<br />
-1<br />
-2<br />
-3<br />
10<br />
-4<br />
10<br />
-5<br />
10<br />
-6<br />
10<br />
Preliminary<br />
s = 7 TeV<br />
Pythia 6<br />
ATLAS Data<br />
Pythia 6<br />
Not corrected for detector effects<br />
MC Sum<br />
ND<br />
SD<br />
DD<br />
SD ND<br />
DD<br />
1 2 3 4 5 6<br />
p<br />
T<br />
[GeV]<br />
• Phojet shows best agreement<br />
over full pT range<br />
• Pythia 8 overestimates at low pT<br />
• Pythia 6 underestimates for most pT<br />
• Pythia 6 diffractive component<br />
very soft<br />
• Agrees fairly well in high pT tail where<br />
ND component dominates<br />
49
]<br />
-2<br />
[GeV<br />
trk<br />
N<br />
d p<br />
2<br />
d<br />
Ratio(MC/Data)<br />
pT Spectrum<br />
T<br />
<br />
d<br />
2 p<br />
1<br />
T<br />
ev<br />
N 1<br />
10<br />
10<br />
1<br />
-1<br />
-2<br />
-3<br />
10<br />
-4<br />
10<br />
-5<br />
10<br />
-6<br />
10<br />
1.5<br />
1<br />
0.5<br />
ATLAS Preliminary<br />
s = 7 TeV<br />
Not corrected for detector effects<br />
Data<br />
Phojet<br />
Pythia 8<br />
Pythia 6<br />
1 2 3 4 5 6<br />
p<br />
T<br />
[GeV]<br />
LBL RPM<br />
05/22/2012<br />
]<br />
-2<br />
[GeV<br />
trk<br />
n<br />
2<br />
d<br />
p<br />
d<br />
<br />
d<br />
2 p<br />
1<br />
T<br />
T<br />
ev<br />
N 1<br />
10<br />
10<br />
10<br />
1<br />
-1<br />
-2<br />
-3<br />
10<br />
-4<br />
10<br />
-5<br />
10<br />
-6<br />
10<br />
Preliminary<br />
s = 7 TeV<br />
Pythia 6<br />
ATLAS Data<br />
Pythia 6<br />
Not corrected for detector effects<br />
MC Sum<br />
ND<br />
SD<br />
DD<br />
SD ND<br />
DD<br />
1 2 3 4 5 6<br />
p<br />
T<br />
[GeV]<br />
• Phojet shows best agreement<br />
over full pT range<br />
• Pythia 8 overestimates at low pT<br />
• Pythia 6 underestimates for most pT<br />
• Pythia 6 diffractive component<br />
very soft<br />
• Agrees fairly well in high pT tail where<br />
ND component dominates<br />
49
Luminosity Stability over 2010<br />
• Variations of 0.5% or less between different<br />
luminosity determinations over full 2010 run.<br />
LBL RPM<br />
05/22/2012<br />
50