heavy ion physics with cms
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Russell Betts Quark Matter 2006
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Heavy Ion Physics with CMSHeavy Ion Physics with CMS
Russell Betts
for theCMS Collaboration
Heavy Ion Physics Institutions
Athens, Auckland, Budapest, CERN, Chongbuk, Colorado, Cukurova, Iowa, Kansas, Korea,
Los Alamos, Lyon, Maryland, Minnesota, MIT, Moscow, Mumbai, Rice, Seoul, Vanderbilt,
UC Davis, UI Chicago, Yonsei, Zagreb
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Heavy Ion Physics at the LHCHeavy Ion Physics at the LHC
•Enormous increase in yields of hard probes
Is the created matter the same as at RHIC?
Yes – Possibility for detailed study of QCD matter discovered at RHIC
No – A new challenge for models
•LHC Energy = 30 RHIC Energy
•Gluon Saturation – even at =0
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CMS Heavy Ion Physics ProgramCMS Heavy Ion Physics Program
• Comprehensive program with emphasis on hard probes• Program follows increasing luminosity• Pb+Pb for the first few years, expect other ions and p+Pb later
Soft Physics and Global Event Characterization Centrality and good Event Selection – Scaling with Npart, Ncoll
Charged Particle Multiplicity – Initial State Gluon Densities Azimuthal Asymmetry (Flow) – Equation of State Spectra + Correlations – Sources, Radial Flow, dE/dx and Quenching
High pT Probes High pT Particles and studies of Jet Fragmentation – Energy Loss and
Modification of Fragmentation Functions. Flavor and Geometry Dependence. Quarkonia (J/, ) and Heavy Quarks – Suppression and Recombination High Energy Photons, Z0, Jet-, Jet-Z0, Multijet Events – Calibrated Measure
of dE/dx
Forward Physics Limiting Fragmentation – Saturation, Color Glass Condensate Ultra Peripheral Collisions – PDF in New Regions of x and Q2
Exotica -
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CASTORCASTOR
T2T2
Collar Collar shieldingshielding
Forward DetectorsForward Detectors
(5.2 < < 6.5)
TOTEMTOTEM
ZDCZDC
(5.3 < < 6.7)
(z = 140 m)
BeamsBeams
EMEM
HADHAD
The CMS DetectorThe CMS Detector
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4T Field
Particle Detection in CMSParticle Detection in CMS
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Detector SpecificationsDetector Specifications
CalorimetryECAL
~80,000 PbWO4 Crystals with APD Readout
HCALBarrel and Endcap (Cu+Scint)Forward Calorimeter (Fe+Quartz)
Zero Degree CalorimeterEM & Hadronic SectionsLuminosity Monitor
Silicon TrackerPixel Detector
Three Pixel (150*100 m2) Layers with Energy Readout. Low Occupancy
Strip DetectorTen Barrel LayersTwelve Endcap Layers
Muon SystemBarrel
Drift ChambersEndcap
Cathode StripsMuon Trigger
Resistive Plate Chambers
Forward DetectorsCASTOR - CalorimeterTOTEM - T2 Tracker
DAQ/TriggerL0,L1 Hardware TriggerHigh Level Trigger
Event Builder and SwitchFilter Farm (~1500 Servers)
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The Real CMSThe Real CMS
HF into the Collision Hall
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Kinematics and AcceptanceKinematics and Acceptance
HCAL (Barrel+Endcap+Forward)
Large Range of Hermetic Coverage
Silicon and Tracker
ECAL
HCAL
CASTOR
ZDC Neutrals
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Heavy Ion Event in CMSHeavy Ion Event in CMS
Pb+Pb event display: Produced in full software framework (simulation, data structures, visualization)
Pb+Pb event (dN/dy = 3500) with -
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Minimum Bias TriggerMinimum Bias Trigger
R Hollis, A Iordanova
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Event SelectionEvent Selection
Energy in HF
Zero Degree Calorimeter
Centrality (Impact Parameter) Determination is needed for Physics Analysis
ET [
GeV
]
Pb+Pb
HF
Correlate ZDC Signal with other Detectors
M Murray - Poster
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CMS TriggerCMS Trigger
HLT provides - Centrality, Event Plane, Vertex Position, dN/dET, Ejet, Muon Tracks…
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Physics Enhancement with Physics Enhancement with Strawman Trigger TableStrawman Trigger Table
G Roland – Parallel Talk
Statistical Significance – 1 Year Production Rates in Pb+Pb
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Global PhysicsGlobal Physics
Event by Event dn/d and dE/dHit Counting and Tracklets in Pixels a la
PHOBOS (Pulse Height in Pixels)
Energy - 5.2 (HF) 6.5 (CASTOR)
C Smith
ch
Extrapolation from RHICC Smith
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Elliptical FlowElliptical Flow
Reaction Plane
= 0.12 rad
S Petrushanko
Will Hydro hold at LHC?
Krofcheck - Poster
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High pHigh pTT Suppression/Tracking Suppression/Tracking
I. Vitev and M. Gyulassy, Phys.Rev.Lett. 89 (2002)
Momentum Resolution
• Efficiency
o Fake Rate
Track-Pointing ResolutionEfficiency/Fake-rate
Inclusive pT Spectra vs Collision Centrality
– Determine Nuclear Modification Factors RAA
– Yield plus High Level Trigger will allow Measurement out to 200 GeV.
C. Roland
250
200
150
100
50
(
m)
pT [GeV/c) pT [GeV/c) pT [GeV/c)
Res
olu
tio
n (
%)
(%
)
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Jet Fragmentation and CorrelationsJet Fragmentation and Correlations
• Fragmentation function for 100GeV jets embedded in dN/dy ~5000 events.
• Jet-jet correlations
C Roland
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Tracking Performance at Low pTracking Performance at Low pTT
Pixel Tracking All Tracker Fitting
Low pT Tracking Using Three Pixel Layers
PID with dE/dx and Topology (V0)
Efficiency
Fake Rate
Sikler - Poster
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Jet ReconstructionJet Reconstruction
PILE-UP SUBTRACTION ALGORITHMPILE-UP SUBTRACTION ALGORITHM1. Subtract average pileup2. Find jets with iterative cone algorithm3. Recalculate pileup outside the cone4. Recalculate jet energy
Measured Jet Energy Efficiency, Purity Jet Energy Resolution
Vardanyan
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Jet Quenching Jet Quenching
High level trigger on high ET jets will extend
physics reach.
e.g RAA to 200 GeV
Statistical Significance – 1 Year
C Roland, Veres - Poster
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Quarkonia (Quarkonia (J/ ))
J/ Acceptance
Kodolova, Bedjidian
SPS
Suppression ?
Regeneration ?
RHICLHC
Energy Density
= 35 MeV/c2
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Quarkonia (Quarkonia ())
Acceptance
Kodolova, Bedjidian
C Loizides
Thy. – Gunion and Vogt
’/
= 54 MeV/c2’
’’
Statistical Reach
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High Mass Di MuonsHigh Mass Di Muons
• Z0 reconstructed with
high efficiency by design• Dimuon continuum dominated
by b decays• High statistics
Kvatadze
Balance Energies of */Z0 and Jet
Mironov - Poster
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Forward PhysicsForward Physics
• Quarkonia photoproduction• Uses ZDC to trigger on
forward emitted neutrons• Measurement -> +-, e+e-
in the central detector• Probes nuclear PDF in
unexplored (x,Q2) range
D’Enterria - Parallel Talk
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SummarySummary
CMS is a Superb and Versatile Detector for Heavy Ion Physics
Excellent performance in high pT(ET) region and for pairs – by design
•Jet Physics•Quarkonia•Z0
Surprising ability for global/soft physics•Global Variables (Nch, ET) over wide range of •Event by event physics – flow etc etc
Unique forward physics capabilities - coverage
Sophisticated trigger will extend physics reach and allow us to focus on key physics issues
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Muons Wide rapidity range || < 2.4 σm~ 50 MeV at
ECAL Barrel
1.48 x= 0.0175 x 0.0175 Resolution: 0.027/E 0.0055
Endcap Preshower 1.652.6
HCAL Barrel+Endcap
x0.087 x 0.087 Resolution: 1.16/E 0.05
Extra – CMS DetectorExtra – CMS Detector
Silicon Tracker Pixel Detector
3 barrel layers and 2 forward layers on each side
100x150 m pixel size Low occupancy: 2% for pixel L1
@ dN/d = 5000
Strip Detector 10 barrel layers of single- and
double-sided silicon, 9 forwardlayers on each side
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Extra – Trigger TableExtra – Trigger Table
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