Observables in heavy-ion collisions at CMS

Haidong Liu

2009-10-21

outline

• The CMS detector

• Review of the ‘golden’ observables

• Other interesting observables for me

• LHC schedule (latest version)

CMS detectors

– Silicon pixel detector– Silicon microstrip tracker– Electromagnetic Calorimeter– Hadronic Calorimeter– Superconducting Solenoid– Muon detectors

• Drift Tubes (barrel)• Cathode Strip Chambers (endcaps)• Resistive Plate Chambers (barrel+endcap

s)

– CASTOR Calorimeter (forward)– Zero Degree Calorimeter (forward) (Jet with cone size R=0.5)

Low pT PID spectra for Pb+Pb @ 5.5 TeV

Event plane resolutionb=9fm of Pb+Pb collisions --the expected resolution is 0.37 rad with ECAL

NA49 Phys. Rev. C 68 034903 PHOBOS nucl-ex/0610037PHOBOS Nucl. Phys. A 774 523–26 STAR AIP Conf. Proc. 870 691–4Voloshin S A and Poskanzer A M Phys. Lett. B 474 27–32Kolb P F, Sollfrank J and Heinz U W ,Phys. Rev. C 62 054909Teaney D, Lauret J and Shuryak E V nucl-th/0110037

Φsimu-Φreco

J. Phys. G: Nucl. Part. Phys. 34 (2007) 2307-2455

high pT charged particle spectra

Expected reach (0.5 nb-1): pT~ 300 GeV/c (inclusive hadrons)

Jet

Jet ET reco resolution Jet ET distributions for 1 month data

Expected quarkonia signalsin one month data (di-muon) Assuming no quarkonia suppression

Solid line: Both μ |η|<2.4 dashed line: Both μ |η|<0.8

Acceptance

J. Phys. G: Nucl. Part. Phys. 34 (2007) 2307-2455

Stat. errors of Y’/Y ratios(a

rbitr

ary

)

Curves are calculations for different initial conditions and different assumption of Tdiss

Z0 μμ signal

1 month data: ~11000 (Z μμ)

J. Phys. G: Nucl. Part. Phys. 34 (2007) 2307-2455

Tagged Jet

An ideal way to measure parton energy loss in the medium

Other interesting observables

• Open charm & bottom– DK+π

– DK+μ+νμ (K μ correlations)

– B+J/psi K+ (BR~0.001)– B0J/psi K0 (BR~0.001)– X-section and flow are both very interesting

• Z boson reconstruction– Ze+e- (BR 3.4%)– ZJets

For B and D reconstruction

pion efficiencies in pp and PbPb collisions

Ks in ppPixel+tracker

1. Low pt track efficiency is not bad2. Ks can be reconstructed nicely3. dEdx can help on PID

DK+e+νe (K e correlations at STAR)

3<pT(e)<6 GeV/c 3<pT(e)<6 GeV/c

Φ<36 degree

PYthia simulation at 200 GeV

DK+e+νe (K e correlations at STAR)

Run5 & Run6 pp data

Z boson reconstruction

• Ze+e- (BR 3.4%)– Large energy electrons (>50 GeV) identificatio

n should be easy

• ZJets– Huge background– Depends on the study of the jet reco algorithm

LHC schedule

• Preparing for mid-November start of beam operations– A few weeks for first collisions from then– First 7 TeV collisions in week before Christmas

break

• Initial operations at 7 TeV (3.5+3.5)– “Energy scan” (0.9, 7, 8-10TeV)

• Pb+Pb run still scheduled at the end of p+p run– Now foreseen to start Nov 1 2010

Thank you

CMS detectors

– Silicon pixel detector– Silicon microstrip tracker– Electromagnetic Calorimeter– Hadronic Calorimeter– Superconducting Solenoid– Muon detectors

• Drift Tubes (barrel)• Cathode Strip Chambers (endcaps)• Resistive Plate Chambers (barrel+en

dcaps)

– CASTOR Calorimeter– Zero Degree Calorimeter

pp@14TeV L~1034cm-2s-1 PbPb@5.5TeV L~1027cm-2s-1

(Jet with cone R=0.5)

Photon tagged jets

Isolated photon+

away side jet

CMS NOTE HIN-07-002

Unquenched FF Quenched FF

models used in this analysisPYQUEN: selected QCD channels w/ jet quenchingPYTHIA: selected QCD channels w/o jet quenchingHYDJET: underlying corresponding Pb+Pb events

Ratio of quenchedand unquenched FF

Detailed quantitative studies of medium-induced parton energy-loss possible.