Heavy Ion Physics with CMS

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

Documents

Heavy Ion Physics with CMS