LHC Heavy-Ion Program a CMS Perspective Edwin Norbeck University of Iowa for the CMS Collaboration 20 th Winter Workshop on Nuclear Dynamics CMS HI groups: Athens, Auckland, Demokritos, Dubna, Lyon, MIT, Moscow, Rice, Tbilisi, U Ioannina, U Iowa, U Kansas, UC Davis, UI Chicago, UC Riverside,
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LHC Heavy-Ion Program a CMS Perspective Edwin Norbeck University of Iowa for the CMS Collaboration 20 th Winter Workshop on Nuclear Dynamics CMS HI groups:
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LHC Heavy-Ion Program a CMS Perspective
Edwin NorbeckUniversity of Iowa
for the CMS Collaboration
20th Winter Workshop on Nuclear Dynamics
CMS HI groups: Athens, Auckland, Demokritos, Dubna, Lyon, MIT, Moscow, Rice, Tbilisi, U Ioannina, U Iowa,
U Kansas, UC Davis, UI Chicago, UC Riverside,
March 15, 2004 20th Winter Workshop Jamaica E. Norbeck U. of Iowa 2
The experiments
ATLAS: pp experiment, HI proposal in progress
ALICE: dedicated HI experiment
CMS: pp experiment with HI program
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The Physics Landscape: Pb+Pb Collisions SPS->RHIC->LHC
d
Extrapolation of RHIC results favors low values
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Heavy Ion Physics at the LHC
J/ψ
Medium modification at high pT Copious production of high pT
particles
Different “melting” for members of family Large cross section for J/ψ and
family production
Correlations, scattering in medium Large jet cross section, jets
directly identifiable
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CMS as a Detector for Heavy Ion Physics
DAQ and Trigger High rate capability for AA,
pA, pp High Level Trigger capable
of full reconstruction of most HI events in real time
Solenoid with Si Tracker,ECAL and most of HCAL inside
chambers
Fine Grained High Resolution Calorimeter
Hermetic coverage up to ||<5 (||<7 proposed using CASTOR) Zero Degree Calorimeter
(proposed)Tracking from Z0, J/,
Wide rapidity range ||<2.4 σm ~50 MeV at
Silicon Tracker Good efficiency and low fake
rate for pT>1 GeV Excellent momentum
resolution p/p~1% for pT<25 GeV and higher
Fully functional at highest expected multiplicitiesDetailed studies at ~3000-5000 and cross-checks at 7000-8000
HF
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CMS under construction
Hadron Calorimeter
Electromagnetic Calorimeter
Si tracker &Pixels
Magnet &Muon Absorber
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CMS Detector in the Heavy Ion Environment
High Multiplicity of Low pT Hadrons
Occupancies still Reasonable
Large Event Size but Lower Event Rate
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CMS as a Heavy Ion Experiment Excellent detector for high pT probes:
High rates and large cross sections quarkonia (J/ ,) and heavy quarks (bb) high pT jets high energy photons Z0
Correlations jet- jet-Z0
multijets Global event characterization
Energy flow to very forward region Charged particle multiplicity Centrality Azimuthal asymmetry
CMS can use highest luminosities available at LHC both in AA and pA modes
-
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Global Measurements: dNch/d (single event) a la Phobos
Use high granularity pixel detectors Use pulse height measurement of pixel clusters to reduce
background Very low pT reach, pT>26 MeV ! (inner pixel layer at R~45 mm)
EclusterPreliminary
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Azimuthal asymmetry, calorimetersUse highly segmented calorimeters to determine event plane
Simulations of Pb+Pb with b=6 fm
=0.1 rad
Event plane determination
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Quarkonia in CMS
J/ family Yield/month (k events, 50% eff)Nominal luminosity for each ion
species
Pb+Pb, 1 month at L=1027
Pb+Pb Kr+Kr Ar+Ar
L 1027 7×1028 1030
J/ 29 470 2200
´ 0.8 12 57
23 320 1400
´ 12 180 770
´´ 7 100 440
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High Mass Dimuon, Z0 Production
Z0-> can be reconstructed with high efficiency
A probe to study nuclear shadowing
Z0 also proposed as reference for production.
Dimuon continuum dominated by b decays
Heavy quark energy loss
High statistics (1 month):
Channel (M> 10 GeV) Barrel + EndcapEvents
Z+- 1.1 104
BB+-, PT>5 GeV 1.2 105
BJ/ψ+-, PT>5 GeV 1.3 105
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Outside-In
Vertex Reconstruction
z=190 m
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Jet Reconstruction in CMS using Calorimeters
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Charged Particle Jet Studies in CMS
Detailed study of phenomena which are already apparent at RHIC Study the centrality dependence of:
Charged particle spectra starting at pT~1 GeV Possibly lower pT cutoff with reduced B field
Back-to-back correlations a la STAR Azimuthal asymmetry vs. pT
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Performance of the Track Reconstruction: Inside-Out
Match Reconstructed tracks to MC input on a hit by hit basis
(Event sample: dN/dy ~3000 + one 100 GeV Jet/Event)
pT/pT < 1% || < 0.7
The increased local track density in a jet-cone leads to a decrease in reconstruction efficiency of ~5-10%
Can be corrected for since jets will be reconstructed by the calorimetry
Tracking efficiency
Fake tracks
Efficiency
Fakes
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Jet fragmentation
Fragmentation function for 100 GeV Jets embedded in dN/dy ~5000 events.
Longitudinal momentum fraction z along the thrust axis of a jet: pT relative to thrust axis:
High precision tracking out to high momenta will allow for detailed jet shape analysis to study the energy loss mechanism
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L1
HLT
Heavy Ion TriggerMain types of trigger as required by physics: