1. IPM, 1 st 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. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 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) «Soft» tests (p T ~Λ QCD =200 МэВ) Low pt particle spectra and particles correlations Flow effects Thermal photons and dileptons Strangeness flow «Hard» tests (p T, M>>Λ QCD =200 МэВ) High-pt particle spactra and its angular correlations Jets Onia Heavy quarks flow Initial state Pre-equilibrium state Heating and density increase:QGP formation hadronization Freeze-out and hadronic state Quark-Gluon Plasma (QGP)

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

4. Overview From RHIC to LHC CMS detector QCD matter in the soft sector dN ch /d  low p T  /K/p spectra Eliptic flow QCD matter in the hard sector high-p T 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. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Some evidences from RHIC Calor Glass Condensate?Local equilibrium in Freeze-out stage? Deflection from Hydro – Viscosity? Same J/  suppression at SPS and RHIC More suppression in forward Strong interaction of Dense matter with High pt hadrons sQGP at RHIC? LHC-? LHC--? Suppression vs regeneration? And many other questions to LHC

6. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 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 (Z 0, W  ) Low x High p T From RHIC (200 GeV/n-n) to LHC (5500 GeV/n-n)

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

8. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Strongest magnetic field: 4 T, 2 T (return yoke) Silicon tracker: Momentum resolution is ~2% for tracks with p T <100 GeV Good efficiency and low fake rate for p T >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 HCAL ECAL Tracker Coil Fine grained high resolution calorimeter with hermetic coverage up to |  |<5 (|  |<7 proposed with CASTOR) ZDC accepted |  |>8.3 Jet finder coverage up to |  |<5 and photons coverage up to |  |<3 Muon stations with: precise measurement of position (momentum) fast response at LVL1 trigger CMS detector for heavy ion physics

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

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

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

12. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Eliptic flow: medium viscosity  x y Initial spatial anisotropy pxpx pypy Final momentum anisotropy Reaction plane x z y dN/d(  -  R ) = N 0 (1 + 2v 1 cos (  -  R ) + 2v 2 cos (2(  -  R )) +... ) Elliptic Flow: v 2 - defines  R, (direction of the impact parameter) LHC

13. IPM, 1 st 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(  1 -  2 )) = v 2 2 Azimuthal E T distribution in different calorimeter layers Event plane resolution with ECAL: 0.37 radian V2 with tracker

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

15. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Hard probes triggering for HI in CMS CMS trigger system is designed for 10 34 (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 1/400 100 KHz, 1MB DAQ/HLT 1/600 150 Hz, 1.5 MB PbPb: Luminosity(cm-2s-1): 10 27 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 1/11/80-1/800

16. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Jet finder in CMS for HI E T rec vs E T gen CMS Iterative cone (R>=0.5) with background subtraction dN ch /d  = 5000 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 Space resolution is less then the size of calorimeter tower

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

18. IPM, 1 st 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. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Photon reconstruction 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: Efficiency = 60% Fake = 3.5% S/B=4.5

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

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

22. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 J/  measurements both muons with  |<2.4 Expected rate (per month,10 6 s, 0.5 nb -1 ): J/  ~ 180 kevents CMS “high” multiplicity dN ch /dη|  =0 = 5000 “low” multiplicity dN ch /dη|  =0 = 2500 Excellent mass resolution:  J/  = 35 MeV/c 2, both muons with |  |<2.4 Signal/Background: ~5(1) for J/  in |  |<0.8 (|  |<2.4) Expected rate (per month, 10 6 s, 0.5 nb -1 ): J/  ~ 180 kevents

23. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 Upsilon measurements mass resolution, 54 MeV “high” multiplicity dN ch /dη|  =0 = 5000 Luminosity 0.5 nb-1 |  |<2.4 mass resolution, 90 MeV |  |<2.4 Y ~ 25 kevents, Y' ~ 7 kevents, Y'' ~ 4 kevents CMS Excellent mass resolution:  Y = 54 MeV/c 2 |  |<0.8,  Y = 90 MeV/c 2 |  |<2.4 Signal/Background: 1 (0.1) for Y in |  |<0.8 (|  |<2.4)

24. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 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 E max ≈ 1. TeV/n (~3×e+p HERA)  : cm E max ≈ 160 GeV (~LEP) Measure the gluon distribution function in the nucleus (  Pb)  low background  simpler initial state  Pb →  photo-production in CMS  Unexplored (x,Q 2 ) regime:  Pin down amount of low-x suppression in the Pb nuclear PDF (compared to the proton PDF) dAueA Ultra-peripheral collisions

25. IPM, 1 st 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, 1 st 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 B-PAG QCD-PAG EWK-PAG Take pp measurements as reference to AA run 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. Z-production: important input for MC heavy ion models

27. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 First Pb-Pb data – NEXT YEAR! First AA run next year 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. ->2

28. IPM, 1 st meeting on LHC Physics, Isphagan,Iran 20 April-24 April 2009 First A-A run 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 μ b –1 Note: nominal run is 0.5 nb -1 ~3kHz ~100Hz Ave. Coll. rate 1 1 Pile up ~2s~8kHz5.5 TeVNominal ~60s~150Hz~ 4 TeVYear-1 CPU/EventMax.Coll. RateColl. EnergyPb+Pb

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

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