July 27, 2002CMS Heavy Ions Bolek Wyslouch1 Heavy Ion Physics with the CMS Experiment at the Large Hadron Collider Bolek Wyslouch MIT for the CMS Collaboration 31 st ICHEP, Amsterdam, July 2002

July 27, 2002CMS Heavy Ions Bolek Wyslouch2 The Physics Landscape: Pb+Pb Collisions SPS->RHIC->LHC 350 dd ?

July 27, 2002CMS Heavy Ions Bolek Wyslouch3 CMS as a Detector for Heavy Ion Physics n High Resolution and High Granularity Calorimetry  x  barrel  u ECAL:0.0174x u HCAL: 0.087x0.087 l Resolution (barrel) u ECAL:0.027/  E  u HCAL:1.16/  E  0.05 Hermetic coverage up to |  |<5 (|  |<7 proposed using CASTOR) l Zero Degree Calorimeter (proposed) Tracking  from Z 0, J/ ,  Wide rapidity range |  |<2.4 Efficient suppression of , K   background u ECAL at 1.3 m from the beam   chambers behind HCAL u reject “kinks” using tracker Excellent M  mass resolution ~50  Si Tracker including Pixels n n DAQ and Trigger l l High rate capability for AA, pA, pp l l High Level Trigger capable of full reconstruction of most HI events in real time ECAL HCAL  chambers

July 27, 2002CMS 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 n CMS can use highest luminosities available at LHC both in AA and pA modes -

July 27, 2002CMS Heavy Ions Bolek Wyslouch5 CMS under construction Hadron Calorimeter Electromagnetic Calorimeter Si tracker & Pixels Magnet & Muon Absorber

July 27, 2002CMS Heavy Ions Bolek Wyslouch6 Beam pipe splits 140m from IR ZDC LOCATION BEAMS Zero Degree Calorimetry for CMS “Spectators” ZDC ZDC

July 27, 2002CMS Heavy Ions Bolek Wyslouch7 Pb+Pb    Higher multiplicity of low pt particles Lower luminosity and event rate HI compared to pp: Extending CMS Event Size CMS is designed for high luminosity pp pp events are large to account for pileup effects

July 27, 2002CMS Heavy Ions Bolek Wyslouch8 Quarkonia in CMS J/   family Yield/month (kevents, 50% eff) Nominal luminosity for each ion species Pb+Pb, 1 month at L=10 27 Pb+PbSn+SnKr+KrAr+Ar L J/  ''  ''  ''

July 27, 2002CMS Heavy Ions Bolek Wyslouch9 Quarkonia from Different Ion Species J/  family

July 27, 2002CMS Heavy Ions Bolek Wyslouch10 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):

July 27, 2002CMS Heavy Ions Bolek Wyslouch11 Jet Reconstruction in CMS n Subtract average pileup n Find jets with sliding window n Build a cone around E T max n Recalculate pileup outside the cone n Recalculate jet energy Window Algorithm Full jet reconstruction in Pb+Pb central collisions (dN/dy~8000) Efficiency Measured jet energy Jet energy resolution Jet spatial resolution:  (  rec -  gen )=0.045,  (  rec -  gen )=0.051 better than size of HCAL tower

July 27, 2002CMS Heavy Ions Bolek Wyslouch12 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

July 27, 2002CMS Heavy Ions Bolek Wyslouch13 Jet Fragmentation, Effect of Nuclear Matter on Jet Structure n Find jets using calorimetry n Study charged particle momenta inside of a jet using the tracker n For this study use 4-5 outer layers of the tracker (use conservative resolution obtained in pp studies: AA plausible with low occupancy in outer layers) Particles in jet Background Similar analysis can be done with  0

July 27, 2002CMS Heavy Ions Bolek Wyslouch14 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 Essentially no modification to the detector hardware l New High Level Trigger algorithms l Zero Degree Calorimeter and CASTOR as relatively minor additions n The knowledge gained at RHIC will be extended to new energy domain

July 27, 2002CMS Heavy Ions Bolek Wyslouch15