January 15, 2004CMS Heavy Ions Bolek Wyslouch1 Bolek Wyslouch MIT for the CMS Collaboration Quark Matter 2004, Oakland, CA CMS HI groups: Athens, Auckland, Demokritos, Dubna, Lyon, MIT, Moscow, Rice, Tbilisi, U Ioannina, U Iowa, U Kansas, UC Davis, UI Chicago, UC Riverside, Heavy Ion Physics with the CMS Experiment at the Large Hadron Collider

January 15, 2004CMS Heavy Ions Bolek Wyslouch2 Heavy Ion Physics at the LHC      J/ψ n Medium modification at high p T l Copious production of high p T particles n Different “melting” for members of  family l Large cross section for J/ψ and  family production n Correlations, scattering in medium l Large jet cross section, jets directly identifiable

January 15, 2004CMS Heavy Ions Bolek Wyslouch3 CMS as a Detector for Heavy Ion Physics Si Tracker including Pixels n DAQ and Trigger l High rate capability for AA, pA, pp l High Level Trigger capable of full reconstruction of most HI events in real time ECAL HCAL  chambers n Fine Grained High Resolution Calorimeter Hermetic coverage up to |  |<5 (|  |<7 proposed using CASTOR) l Zero Degree Calorimeter (proposed) Tracking  from Z 0, J/ ,  Wide rapidity range |  |<2.4 l σ m ~50 MeV at  n Silicon Tracker n Good efficiency and low fake rate for p T >1 GeV Excellent momentum resolution  p/p~1% for p T <25 GeV and higher Fully functional at highest expected multiplicities Detailed studies at ~ and cross-checks at

January 15, 2004CMS Heavy Ions Bolek Wyslouch4 CMS as a Heavy Ion Experiment n Excellent detector for high p T probes: l High rates and large cross sections  quarkonia (J/ ,  ) and heavy quarks (bb) u high p T jets u high energy photons u Z 0 l Correlations  jet-  u jet-Z 0 u multijets n Global event characterization l Energy flow to very forward region l Charged particle multiplicity l Centrality l Azimuthal asymmetry n CMS can use highest luminosities available at LHC both in AA and pA modes -

January 15, 2004CMS Heavy Ions Bolek Wyslouch5 CMS under construction Hadron Calorimeter Electromagnetic Calorimeter Si tracker & Pixels Magnet & Muon Absorber

January 15, 2004CMS Heavy Ions Bolek Wyslouch6 CMS Very Forward Region CASTOR, TOTEM and ZDC CASTOR Coverage CASTOR n Multiplicity and hermetic coverage to |η|<7 n Zero Degree Energy n Physics: l Centrality l Limiting Fragmentation l Peripheral and ultra-peripheral collisions l Low-x, Color-Glass Condensate l DCC, Centauros, Strangelets Poster: M. Murray

January 15, 2004CMS Heavy Ions Bolek Wyslouch7 CMS Very Forward Region CASTOR, TOTEM and ZDC ZDC TOTEM: Roman Pots

January 15, 2004CMS Heavy Ions Bolek Wyslouch8 Global Measurements: dN ch /d  (single event) a la Phobos n Use high granularity pixel detectors n Use pulse height measurement in individual pixels to reduce background n Very low p T reach, p T >26 MeV ! (inner pixel layer at R~45 mm) E pixel Preliminary

January 15, 2004CMS Heavy Ions Bolek Wyslouch9 Azimuthal asymmetry, calorimeters n Use highly segmented calorimeters to determine event plane n Simulations of Pb+Pb with b=6 fm  =0.1 rad Event plane determination

January 15, 2004CMS Heavy Ions Bolek Wyslouch10 Performance of the Track Reconstruction: Inside-Out n Match Reconstructed tracks to MC input on a hit by hit basis l (Event sample: dN/dy ~ one 100 GeV Jet/Event)  p T /p T < 1% |  | < 0.7 l The increased local track density in a jet-cone leads to a decrease in reconstruction efficiency of ~5-10% l Can be corrected for since jets will be reconstructed by the calorimetry Tracking efficiency Fake tracks Poster: C. Roland Efficiency Fakes

January 15, 2004CMS Heavy Ions Bolek Wyslouch11 Outside-In Vertex Reconstruction  z =190  m

January 15, 2004CMS Heavy Ions Bolek Wyslouch12 Quarkonia in CMS J/   family Expect ~24k J/  and ~ 18/5/3 k ,  ’,  ’’ After one month of Pb+Pb running at L =10 27 cm -2 s -1 with 50% efficiency  Family region M  +  - Poster: M. Bedjidian   Y =50 MeV J/  acceptance

January 15, 2004CMS Heavy Ions Bolek Wyslouch13 High Mass Dimuon, Z 0 Production Z 0 ->  can be reconstructed with high efficiency l A probe to study nuclear shadowing l Z 0 also proposed as reference for  production. n Dimuon continuum dominated by b decays l Heavy quark energy loss n High statistics (1 month): Channel (M  > 10 GeV)Barrel + Endcap Events Z+-Z+ BB  +  -, P  T >5 GeV B  J/ψ  +  -, P  T >5 GeV

January 15, 2004CMS Heavy Ions Bolek Wyslouch14 Jet Reconstruction in CMS using Calorimeters

January 15, 2004CMS Heavy Ions Bolek Wyslouch15 Charged Particle Jet Studies in CMS n Detailed study of phenomena which are already apparent at RHIC n Study the centrality dependence of: l Charged particle spectra starting at p T ~1 GeV u Possibly lower p T cutoff with reduced B field l Back-to-back correlations a la STAR l Azimuthal asymmetry vs. p T

January 15, 2004CMS Heavy Ions Bolek Wyslouch16 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: p T relative to thrust axis: High precision tracking out to high momenta will allow for detailed jet shape analysis to study the energy loss mechanism

January 15, 2004CMS Heavy Ions Bolek Wyslouch17 Balancing  or Z 0 vs Jets: Quark Energy Loss E Tjet,  >120 GeV in the barrel Jet+Z 0 , Z 0 1 month at cm -2 s -1 Pb+Pb

January 15, 2004CMS Heavy Ions Bolek Wyslouch18 Conclusions n LHC will extend energy range and in particular high p T reach of heavy ion physics n CMS is preparing to take advantage of its capabilities l Excellent coverage and resolution u Quarkonia u Jets l Centrality, Multiplicity, Energy Flow reaching very low p T l Essentially no modification to the detector hardware l New High Level Trigger algorithms l Zero Degree Calorimeter, CASTOR and TOTEM as important additions extending forward coverage l Heavy Ion program is well integrated into overall CMS Physics Program n The knowledge gained at RHIC will be extended to the new energy domain