1. Heavy Ion Physics with CMS Russell Betts - UIC

2. Studying QCD with Heavy Ions Quark Gluon Plasma: –QCD at High T, High Density –Phase Diagram of QCD Strongly-Interacting Systems –Evolution of Colliding Nuclei –Study Early-Stage Dynamics hadrons  quark/gluon (F. Karsch, hep-lat/0106019)

3. The Physics Landscape: Pb+Pb Collisions SPS->RHIC->LHC dd Extrapolation of RHIC results favors low values

4. Production of High p T Particles: (e.g  0 ) Enormous Increase at High p T over RHIC and SPS

5. Hot Nuclear Matter Diagnostics Leading Particle Hadrons q q Leading Particle Jet cross-section calculable in QCD Study fate of jets in hot, dense matter in Au+Au Hadrons q q Leading Particle Correlations as Function of Collision Geometry (Thickness Traversed by Particles)

6. Suppression Patterns of Quarkonia J/   family A+A/p+p Distinguish Between Scenarios of Suppression

7. CMS as a Detector for Heavy Ion Physics Si Tracker including Pixels ECAL HCAL  chambers Fine Grained High Resolution Calorimeter Hermetic coverage up to |  |<5 (|  |<7 proposed using CASTOR) Zero Degree Calorimeter (proposed) Tracking  from Z 0, J/ ,  Wide rapidity range |  |<2.4 σ m ~50 MeV at  Silicon Tracker Preliminary Results Very Promising DAQ and Trigger High rate capability for AA, pA, pp High level trigger can reconstruct most AA events in real time

8. Excellent Detector for High p T Probes: –Quarkonia (J/ ,  ) and Heavy Quarks (bb) –High p T Jets –High Energy Photons –Z 0 Hermetic Calorimetry - Correlation of Jets with Jets, , Z 0 Global Event Characterization –Energy Flow in Wide Rapidity Range –Charged Particle Multiplicity – dN/d  – and Flow –Centrality (Collision Geometry) CMS can use Full Luminosities for both AA & dA Physics Measurements in CMS -

9.    CMS Detector in the Heavy Ion Environment High Multiplicity of Low p T Hadrons Occupancies still Reasonable Large Event Size but Lower Event Rate

10. Jets are easily seen in pp … and also in PbPb

11. 1. Subtract average pileup 2. Find jets with sliding window 3. Build a cone around E tmax 4. Recalculate pileup outside the cone 5. Recalculate jet energy Spatial resolution: σ φ = 0.032 σ η = 0.028 Efficiency, purity Jet energy resolution Full Jet Reconstruction in Central Pb-Pb Collision HIJING, dN ch /d  = 5000

12. High Mass Dimuon, Z 0 Production Z 0  can be reconstructed with high efficiency. Dimuon continuum dominated by b decays –Heavy quark energy loss High statistics (1 month): Channel (M   10GeV) Barrel+Endcap ZZ 1.1  10 4 BB      P t (  )  5 GeV1.2  10 5 B  J/       P t (  )  5 GeV 1.3  10 5

13. ChannelBarrel+Endcap Jet+Jet, E T (Jet) >100 GeV 8.7  10 6  +Jet, E T (Jet) >100 GeV6  10 3 Z(      Jet, E T (Jet),P T (Z) >100 GeV 90 Z(      Jet, E T (Jet),P T (Z) >50 GeV 600 Balancing  or Z 0 vs Jets: Quark Energy Loss , Z 0 1 month at 10 27 cm -2 s - 1 Pb+Pb Jet+Z 0

14. Quarkonia from Different Ion Species J/  family

15. Quarkonia in CMS J/   family Yield/month (k events, 50% eff) Nominal luminosity for each ion species Pb+Pb, 1 month at L=10 27 Pb+PbKr+KrAr+Ar L 10 27 7×10 28 10 30 J/  294702200 ´´ 0.81257  233201400 ´´ 12180770  ´´ 7100440

16. Si Tracker Performance with Heavy Ions 6 layers Outer Barrel 4 layers Inner Barrel 3 disks 9 disks in the End Cap 1 Single Detector 2 Detectors Back to Back Pixel Layers Crucial for Heavy Ions

17. Construct “Tracklets” using two outer pixel layers - straight lines in R-z - and calculate z BEAM for each. Iterative histogramming draws out peak Fit with Gaussian + constant to find z vertex Optimize p T (min) and  range to balance statistics vs. combinatorics Tracklets constructed from triplets reduce combinatorial background Primary Vertex Reconstruction Multiplicity (dN/d  )2000300050007000 RMS (  m)16.314.113.012.6

18. Tracking with CMS pp Track Finder Uses “Triplet” Track Seeds “Reconstructable” Tracks have 8 Layers Hit Including 3 Pixel Layers

19. p T Inside a Jet 100 GeV

20. Heavy Ion Specific Additions Zero Degree Calorimeters CASTOR High Level Trigger Software

21. Beam pipe splits 140m from IR ZDC LOCATION BEAMS b 2R ~ 15fm Spectators Participant Region Measure Spectator Neutrons at 0° Correlate E ZDC with Impact Parameter

22. CASTOR and T2 CASTOR 5.32 < η < 6.86 T2 Tracker 5.32 < η < 6.71 New Opportunity: Forward Silicon Counters and Calorimetry Full Multiplicity Coverage up to  of 6.7

23. Heavy Ion Trigger Main types of trigger as required by physics: –multiplicity/centrality:”min-bias”, “central-only” –high p T probes: muons, jets, photons, quarkonia etc. High occupancy but low luminosity ! –many low level trigger objects may be present, but less isolated than in p+p, Level 1 might be difficult for high p T particles –but we can read most of the events up to High Level Trigger and do partial reconstruction HLT for HI needs significant software/simulation effort. L1 HLT

24. People and Institutions Russia: Moscow State University, Dubna France: Lyon Georgia: Tbilisi New Zealand: Auckland Greece: Athens, Demokritos, Ioannina USA NP: Rice, UC Davis, MIT, UI Chicago, U Iowa, UC Riverside, U Kansas Presently ~30 people involved directly in studies/discussions etc. Expect to grow to ~100 by the time LHC starts

25. SUMMARY CMS will Function very well as a Detector for HI Physics. Present RHIC data indicates that high p T HI physics is likely to be a rich field at LHC, which plays to strength of CMS. Number of Heavy Ion Physicists in CMS is growing. Group will be very active. Additional forward detectors for HI will also be interesting and useful for p+p.