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The CMS Heavy Ion Program

The CMS Heavy Ion Program. Michael Murray Kansas. CMS is a running experiment. Overview . The detector Soft Physics Multiplicity ,k,p at low pt Flow Hard Physics Jets Photons Quarkonia Photon nucleus. Z Jet Event. A new telescope for new probes. High Rate, Trigger. Y=4.

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The CMS Heavy Ion Program

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  1. The CMS Heavy Ion Program Michael Murray Kansas

  2. CMS is a running experiment

  3. Overview • The detector • Soft Physics • Multiplicity • ,k,p at low pt • Flow • Hard Physics • Jets • Photons • Quarkonia • Photon nucleus Z Jet Event

  4. A new telescope for new probes High Rate, Trigger Y=4 Rapidity Range

  5. LHC RHIC SPS Hard probes are rare

  6. The Central Detector Pixels Coil Strips Muons EM Cal Iron HCal

  7. A transverse slice through CMS

  8. A slice along Z Coil HCAL ECAL Tracker

  9. Forward Detectors ZDC >8.3 Castor 5.2<<6.6

  10. Multiplicity/event HIJING default settings Find hits in pixels, using an energy cut. We also have a tracklet analysis. Pixels hits count Pseudo rapidity

  11. Low pT hadrons dN dpT Find tracks in pixels and use energy loss vs momentum for particle ID Efficiency pT (GeV/c) |h|<1  pT pT (GeV/c) pT (GeV/c)

  12. z Reaction plane y x Elliptic Flow 1. Find the reaction plane calorimeters and tracker 2. Use 2, 4 particle correlations or Lee Yang Zeros Ecal  0.37 d dE V2 with tracker V2 pT (GeV/c)  rad

  13. Triggering Trigger increases pT range by > 2 for many probes

  14. Finding Jets • Iterative cone (R>=0.5) with background subtraction: • 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 Rec ET dNch/dh = 5000 MC Jet ET (GeV) Space resolution is less then the tower size

  15. 1.0 Tracking Y (m) Single strips Double strips Pixels 0.5 2.0<<2.5 0.5 1.0 • pT • % Z (m) <0.5 Pointing useful for heavy quarks <0.5 Fakes % Efficiency % • z • cm Efficiency ~ 70 %, fake rate ~ 1% pT (GeV/c) pT (GeV/c)

  16. High Pt Charged particles ||<2.5 Assume luminosity = 0.5 nb-1 jet trigger data Energy loss from HYDJET 10% Central RAA No trigger RAA pT (GeV/c) pT (GeV/c)

  17. Efficiency = 60% Fake = 3.5% S/B=4.5 Photons Photon ID based only on cluster shape and isolation cuts using a multi-variate analysis. We reconstruct photon energy with Island algorithm

  18. Jet fragmention from  jet events Require photon ET > 70GeV I =0..5 nb-1

  19. Suppression: RHIC similar to SPS Regeneration compensate screening J/ not screened at RHIC (TD~2Tc) LHC: recombination or suppression  Large Cross-section: 20 x RHIC  melts only at LHC: TD~4 TC Fewer of bb pairs: less regeneration Much cleaner probe than J/ Suppression of B’onium states c Quarkonia Suppression of charmonion y' • J/ Branching ration is 5.9% for J/y , 2.5%Y (BR:2.5%) Background is from decays from p/K, b-,c-mesons

  20. J/  +- = 35 MeV ||<2.4 For 0.5 nb-1 we reconstruct 180K J/ Signal/Background: ~5 for ||<0.8, 1 for ||<2.4 dNch/d = 2500 Produced Reconstructed 2500 Reconstructed 5000 dNch/d = 5000 pT (GeV/c) M(GeV)

  21. Y  +- Y ~ 25 000, Y' ~ 7 000, Y'' ~ 4 000 Signal/Background: 1 ||<0.8, 0.1 for ||<2.4) Produced Reconstructed 2500 Reconstructed 5000 ||<2.4,  = 90MeV ||<2.4 mass resolution, 90 MeV M(GeV) pT (GeV/c)

  22. Photon nucleus Max photon energy ~ 80 GeV Pb: S ≈ 1. TeV/n S ≈160 GeV Mee(GeV) M(GeV)

  23. Multiplicity Soft spectra Flow Forward Physics Quarkonia Hard spectra Photons Jets Z Summary CMS has an excellent opportunity to study partonic matter at both soft and hard scales, via

  24. Backup slides

  25. 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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