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Heavy Ion Physics with the CMS detector

Heavy Ion Physics with the CMS detector. Olga Kodolova, INP MSU. for Collaboration.

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Heavy Ion Physics with the CMS detector

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  1. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Heavy Ion Physics with the CMS detector Olga Kodolova, INP MSU for Collaboration

  2. The temperature and energy density in A-A interactions may be high enough to get the super-dense QCD state in the quasi-macroscopic volumes - QGP (in comparing with hadrons scale) Quark-Gluon Plasma (QGP) Freeze-out and hadronic state Heating and density increase:QGP formation Initial state Pre-equilibrium state hadronization «Hard» tests(pT, M>>ΛQCD=200 МэВ) • High-pt particle spactra and its angular • correlations • Jets • Onia • Heavy quarks flow «Soft» tests (pT~ΛQCD=200 МэВ) • Low pt particle spectra and particles • correlations • Flow effects • Thermal photons and dileptons • Strangeness flow IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009

  3. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009

  4. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Overview From RHIC to LHC CMS detector QCD matter in the soft sector dNch/dh low pTp/K/p spectra Eliptic flow QCD matter in the hard sector high-pT hadrons, jets, photon-jet Qqbar suppression Y-l+l- photoproduction Note: For most of measurements in AA we will need the reference measurements in pp (see talk of Klaus Rabbertz “QCD Physics potential in CMS) High and low pt tracking Muon reconstruction Jet reconstruction Photon reconstruction Event plane Event centrality

  5. Some evidences from RHIC Deflection from Hydro – Viscosity? Local equilibrium in Freeze-out stage? Calor Glass Condensate? Strong interaction of Dense matter with High pt hadrons sQGP at RHIC? LHC-? Same J/y suppression at SPS and RHIC More suppression in forward LHC--? Suppression vs regeneration? And many other questions to LHC IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009

  6. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 From RHIC (200 GeV/n-n) to LHC (5500 GeV/n-n) Low x LHC RHIC SPS • Initial state fully in the saturated CGC regime • Initial energy density ~5 times higher • Lifetime of a quark-gluon plasma much longer • Large rates of hard probes over a broad kinematical range • Plenty of heavy quarks (b,c) • Weakly interacting probes become available (Z0, W) High pT

  7. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 CMS detector 5.3 << 6.7 TOTEM CASTOR ZDC Large Range of Hermetic Coverage: Tracker, muons  ECAL +HCAL  Forward HCAL  CASTOR  ZDC 8.3< 8.3 < 5.2 << 6.6

  8. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 CMS detector for heavy ion physics Strongest magnetic field: 4 T, 2 T (return yoke) Silicon tracker: Momentum resolution is ~2% for tracks with pT <100 GeV Good efficiency and low fake rate for pT>1 GeV/c low occupancy of pixel detectors – 1-2% with PbPb central events Good separation of Onia families High level trigger capable of full reconstruction of most of HI events in real time Excellent possibility for hard probes triggering Coil HCAL ECAL Tracker Fine grained high resolution calorimeter with hermetic coverage up to |h|<5 (|h|<7 proposed with CASTOR) ZDC accepted |h|>8.3 Jet finder coverage up to | h|<5 and photons coverage up to | h|<3 Muon stations with: precise measurement of position (momentum) fast response at LVL1 trigger

  9. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Bulk (“hydro”) measurements in AA collisions

  10. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Charged particle multiplicity ~ gluon density Pixels hits count HIJING default settings CGC prediction First measurement at LHC Simple measurements via hits count in pixels accomplished with dE/dx cut or tracklets with vertex constraints 11 cm Endcap pixels Barrel pixels Beam Final AA multiplicity ~ gluon density

  11. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Soft hadron spectra (CMS) ~ medium equation of state Single hadron (p+-, K+-, p ) pT spectra in pT~0.2-2 GeV/c PID via dE/dx (Gaussian unfolding) |h|<1 Collective radial flow, hadron ratios, thermalization time, medium equation of state constraints

  12. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Eliptic flow: medium viscosity z Reaction plane y x Elliptic Flow: v2 Initial spatial anisotropy y  x - defines R, (direction of the impact parameter) Final momentum anisotropy py px dN/d( - R ) = N0 (1 + 2v1cos (- R) + 2v2cos (2(- R)) + ... ) LHC

  13. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Eliptic flow Two methods: 1. Using reaction plane determination with Calorimeters and tracker 2. Cumulant analysis: using two and multi particle correlations cos(2(f1-f2)) = v22 Event plane resolution with ECAL: 0.37 radian V2 with tracker Azimuthal ET distribution in different calorimeter layers

  14. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Hard probes of QCD matter: Qaurkonia and heavy quarks Jets and high-pT hadrons

  15. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Hard probes triggering for HI in CMS CMS trigger system is designed for 1034 (pp events) with 40 MHz bunch crossing rate. Two levels system: Level 1 and High Level Trigger pp 40 MHz DAQ/HLT 100 KHz Offline 150 Hz Level 1 1/400 DAQ/HLT 1/600 150 Hz, 1.5 MB 100 KHz, 1MB PbPb: Luminosity(cm-2s-1): 1027 Event rate (KHz): 8 Event size after L1(MB): 2.5 (Minbias) 10 (Central) Pb-Pb 8 KHz DAQ/HLT 8 KHz Offline 10—100 Hz 1/1 1/80-1/800

  16. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Jet finder in CMS for HI • Iterative cone (R>=0.5) with background subtraction: • mean value is determined on an • event-by-event basis: • calculate average energy and dispersion in • tower (in eta rings) for each event • subtract average energy and dispersion • from each tower • find jets with a jet finder algorithm (any) • using the new tower energies • recalculate average energy and dispersion • using towers free of jets • recalculate jet energies • Done, but can do more iterations CMS Iterative cone (R>=0.5) with background subtraction ETrec vs ETgen dNch/dh = 5000 Space resolution is less then the size of calorimeter tower

  17. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 High-pt tracking 3 pixel layers in barrel, 2 pixel layers in endcap Silicon layers: 10 in barrel 11 in endcap Resolution: barrel – 1% endcap 2-2.5% Efficiency ~ 70 %, fake rate ~ 1%

  18. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 High-pt hadron spectra different centrality bins for 0.5 nb-1 jet trigger data Jet energy loss model in HYDJET Nuclear modification function reach for 0.5 nb-1

  19. Photon reconstruction Efficiency = 60% Fake = 3.5% S/B=4.5 Photon reconstruction with Island Algorithm Photon ID using Multi-Variate Analysis with 21 variables grouped into 3 sets: ECAL cluster shape and ECAL/HCAL/Tracker isolation cuts Performance: IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009

  20. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Fragmentation function measurements FF(x) FF(z) g+jet events are used UE background subtracted using R=0.5 cone transverse to jet direction Functions are relative to photon energy RFF(x) Integrated luminosity 0.5 nb-1

  21. Dissociation of quarkonia: hot QCD thermometer Suppression: RHIC comparable to SPS Regeneration compensate screening J/ not screened at RHIC (TD~2Tc) LHC: recombination or suppression  Large Cross-section: 20×RHIC  melts only at LHC: TD~4 TC Less amount of bb(bar) pairs: less regeneration Much cleaner probe than J/ Suppression of B’onium States c Suppression of C'onium states Suppression of B'onium states y' • J/ • Quarkonia: J/y (BR:5.9%), Y (BR:2.5%) • Background: combinatorial due- to decays from p/K, b-,c- production IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009

  22. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 J/y measurements • “low” multiplicity • dNch/dη|h=0 = 2500 • “high” multiplicity • dNch/dη|h=0 = 5000 Excellent mass resolution: J/= 35 MeV/c2,both muons with ||<2.4 CMS Signal/Background: ~5(1) for J/y in ||<0.8(||<2.4) Expected rate (per month, 106s, 0.5 nb-1): J/y ~ 180 kevents Expected rate (per month,106s, 0.5 nb-1): J/y ~ 180 kevents both muons with ||<2.4

  23. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Upsilon measurements • “high” multiplicity • dNch/dη|h=0 = 5000 • Luminosity • 0.5 nb-1 Excellent mass resolution: Y= 54 MeV/c2||<0.8, Y= 90 MeV/c2||<2.4 CMS mass resolution, 54 MeV Signal/Background: 1 (0.1) for Y in ||<0.8(||<2.4) ||<2.4 CMS mass resolution, 90 MeV CMS ||<2.4 Y ~ 25 kevents, Y' ~ 7 kevents, Y'' ~ 4 kevents

  24. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Ultra-peripheral collisions • At LHC the accelerated Pb nucleus can produce strong electromagnetic field • due to the coherent action of the Z = 82 proton charges • Equivalent photon flux Emax ~ 80 GeV • Pb: cm Emax ≈ 1. TeV/n (~3×e+p HERA) • : cm Emax≈160 GeV (~LEP) • Measure the gluon distribution function in the nucleus (Pb) • low background • simpler initial state • Pb→ photo-production in CMS • Unexplored (x,Q2) regime: • Pin down amount of low-x suppression in the Pb nuclear PDF (compared to the proton PDF) dAu eA

  25. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Summary The excellent capabilities of CMS give the unique possibility of measuring both soft and hard probes of the dense medium state: Multiplicity soft and hard spectra of charged particles photons Jets Quarkonia some other probes that are not covered by presentation: Dihadron and dijet correlations HBT Heavy Ion Physics program at LHC starts with the FIRST pp data Post-Summary – next Slide

  26. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Post-Summary Heavy ion physics starts with pp runs ! Taking into account the first AA run first pp data are extremely important for success in first AA run 200 pb-1 Take pp measurements as reference to AA run B-PAG Crucial quarkonia measurements pt-eta spectra primary and secondary J/y production Multiplicity, charged particle spectra (low and high), important input for MC heavy ion models. Jet fragmentation, jet shape, jet spectra as input for RAA measurements. QCD-PAG EWK-PAG Z-production: important input for MC heavy ion models

  27. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 First Pb-Pb data – NEXT YEAR! First AA run next year ->2 Note from Chamonix meeting: Early Pb Beam will have lower energy. 10TeV pp corresponds to 4 TeV in Pb+Pb • First Heavy Ion run is scheduled for 2010 • Running at nominal PbPb conditions expected in 2012 • Main tasks for the next half an year is to prepare HLT/DAQ • and to identify the first AA run papers.

  28. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 First A-A run Pb+Pb Coll. Energy Max.Coll. Rate Ave. Coll. rate Pile up CPU/Event Year-1 ~ 4 TeV ~150Hz ~100Hz 1 ~60s Nominal 5.5 TeV ~8kHz ~3kHz 1 ~2s • The low interaction rate in year-1 should allow us to write all min bias events to mass storage • Deploy full HI HLT to tag events and to test efficiencies and functionality • Fully functional HLT needed at nominal luminosity • We need to estimate carefully what analyses can be done with statistics of • 8-80 mlns of events: 1-10 μb–1 • Note: nominal run is 0.5 nb-1

  29. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Backup slides

  30. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 CMS detector for heavy ions Silicon Tracker (Pixels and Strip) Electromagnetic Calorimeter (PbWO4) Central hadron Calorimeter (plastic + brass absorber) Forward calorimeter (Quartz-fiber and ferum) Muon Chambers (Drift tubes in barrel, Cathod strip chambers in endcap, RPC) CASTOR Zero-degree calorimeter + TOTEM 4 T magnetic field (solenoid), 2 T return yoke momentum resolution < 2% for pT<100 GeV Fast DAQ allows to take almost all events to HLT farm

  31. IPM, 1st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 CMS acceptance CMS: Inner detector (|h|<2.5) ECAL (|h|<3) HCAL (|h|<3) HF (3<|h|<5) Muon (|h|<2.4) Castor (5<|h|<6.7) ZDC (|h|>8) Inner detector HF ECAL, PbWO4 0.0174x0.0174 HF Castor Castor HCAL (sampling) 0.087x0.087 (HB) 0.087->0.17 (HE) Muon Spectrometer

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