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CMS 2008:2014 Michael Murray

CMS 2008:2014 Michael Murray. Athens,Basel, CERN, Demokritos, Dubna, Ioannina, Kent State, Kiev, Lyon, MIT, Moscow, N. Zealand, Protvino, PSI, Rice, Sofia, Strasbourg, Kansas, Tbilisi, UC Davis, UC Riverside, UI Chicago, U. Iowa, Yerevan, Warsaw. Are our projections reliable?.

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CMS 2008:2014 Michael Murray

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  1. CMS 2008:2014 Michael Murray Athens,Basel, CERN, Demokritos, Dubna, Ioannina, Kent State, Kiev, Lyon, MIT, Moscow, N. Zealand, Protvino, PSI, Rice, Sofia, Strasbourg, Kansas, Tbilisi, UC Davis, UC Riverside, UI Chicago, U. Iowa, Yerevan, Warsaw

  2. Are our projections reliable? “These theories (this talk) ain’t worth a bucket of worm piss” Bill Willis CERN Council 1982 “There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things we know we don't know. But, there are also unknown unknowns. These are things we don't know we don't know.” Donald Rumsfeld Washington 2002 It’s the unexpected stuff that is fun.

  3. A Generic Detector Muons EM Cyrostat Tracker 17 pp collisions each 25ns = 20% of a PbPb collision Hadron Calorimeter

  4. What do we want to run? The first pp collisions should be April 2007 and PbPb expected one year later. Each year expect several weeks of ion beams (106s effective). The CERN HI community wants a short exploratory run in 2007 Future includes other ion species and pA. Start off with surveys of such as flow, J/ etc. We will then move onto statistics limited measurements such as, , high pT, jets, and correlations of jets with  and Z.

  5. It is vital to understand pp well At RHIC we had some idea what to expect but still had to learn pp. At LHC pp √S is 7 times greater than FNAL.

  6. Measure leptons, hadrons & neutrals

  7. p0 p0 p0 p0 Abundant hard probes  J/

  8. <E>=0 GeV <E>=4 GeV Background <E>=8 GeV # Events/4 GeV Isol. p0+jet ETg/p0-ETJet (GeV) Balancing g or Z0 vs Jets: Quark Energy Loss

  9. J/  Suppression (or enhancement) of quarkonia can tell us about the medium. J/ AA pp Di-muon mass m = 50MeV for the .  Energy Density (GeV/fm3)

  10. Jets in the calorimeters: ||<5 100 GeV Jet PbPb dN/d =5000

  11. Jet Reconstruction Eff % 1. Subtract average pileup 2. Find jets with sliding window 3. Build a cone around Etmax 4. Recalculate pileup outside the cone 5. Recalculate jet energy E % Spatial resolution: = 0.045 = 0.051 Jet ET (GeV)

  12. Event plane determination s =0.1 rad Use calorimeters and tracking to measure V2 CMS

  13. Fragmentation & hydrodynamics Calos cover 14 units of  dN dNpartD

  14. Event by Event Multiplicity (and ET) dN/dh PHOBOS: Single Layer ~15000 channels h Min pT=26 MeV CMS: Three Layers ~60 Million channels

  15. LHC? Measure multiplicity on day 1 Extrapolated to LHC: dN/dh~1400

  16. Evidence for Saturation NdAu Npp

  17. Kinematics at the LHC Access to widest range of Q2 and x Z0  J/y Gluon density has to saturate at low x Saturation

  18. Where do the protons go? At RHIC the protons lose about two units of rapidity. CASTOR covers 5< <7. This should cover the maximum baryon density Rapidity Loss Beam Rapidity

  19. At zero degrees study energy flow and trigger on ultraperipheral Participant Region Spectators b 2R ~ 15fm ZDC LOCATION Spectators BEAMS ~7*107 J/ and  can be made Beam pipe splits 140m from IR

  20. Fragmentation of jets dN dpTjet dN dZ pTjet A jet covers ~ 9000 crystals

  21. Physics Goals of CMS 2008:2014 Observe the weakly interacting QGP. This state may be characterized by a collapse of directed flow, thermalization of charm and stronger energy loss. Use jets,  resonances Z0 and photons to measure its properties. Pin down the color glass condensate by measuring the saturation scale as a function of rapidity (x) and system size. Be ready for unknown unknowns.

  22. Backups

  23. 3 disks 9 disks in the End Cap Si Tracker Performance with Heavy Ions 1 Single Detector 6 layers Outer Barrel 4 layers Inner Barrel 2 Detectors Back to Back Pixel Layers Crucial for Heavy Ions

  24. pT Inside a Jet 100 GeV

  25. Heavy Ion Trigger • Main types of trigger as required by physics: • multiplicity/centrality:”min-bias”, “central-only” • high pT 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 pT 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

  26. Tracking works well for pT > 1GeV

  27. Refinement of RHIC results at the LHC: What lies beyond ? • Many phenomena measured at RHIC have surprisingly simple energy dependence, will this continue at the LHC ? • Hydrodynamic limit, will it hold? Charged particle multiplicity, scaling, limited fragmentation dNch/dh ¢/<Npart>/2 Flow

  28. CASTOR and Totem T2 T2 Tracker 5.32 < η < 6.71 CASTOR 5.32 < η < 6.86 • Forward coverage: • Access to region of relatively high baryon density in HI collisions • Study diffractive & low-x (<106) Physics in p-p interactions

  29. ZDC integration with TAN

  30. Level-1 Trigger • Fast algorithms: 3 ms with coarse local data • Only Calorimetry and Muon Detectors • Special purpose hardware (ASICS) • Centrality with ECAL, HCAL (including HF) • ZDC for minbias. • Trigger on e, m, jets, Missing ET. Rates steep function of pT thresholds • AA higher backgrounds

  31. All event data available: Fine data for Calorimetry and Muon Detectors Tracker Refine triggered object Allows to go lower in pT Processing time O(s) Filtering Farms of commodity processors (Linux) High Level Trigger (HLT) • L1 in AA has larger backgrounds than in pp due to underlying event. • Efficiency trigger requires more careful analysis. HLT can do a better job than L1. • HLT to play a greater role in AA

  32. Illustration Of Online Farm Power: Low pTJ/ψ • Only a small fraction of produced J/ψ are seen in LHC detectors • E.g. CMS J/ψ→mm acceptance 0.1-0.2%, ~O(104) per LHC run • Detection of low pT J/ψ requires efficient selection of low momentum, forward going muons. Simple hardware L1 dimuon trigger is not sufficient Without online farm (HLT) With online farm (HLT) Online farm Online farm Improvement Acceptance x2.5 h pT

  33. 1. Subtract average pileup 2. Find jets with iterative cone algorithm 3. Recalculate pileup outside the cone 4. Recalculate jet energy Calorimetric Jet reconstruction PILE UP SUBTRACTION ALGORITHM Jet energy resolution Efficiency, purity Measured jet energy Jet spatial resolution: (rec- gen) = 0.032;(rec- gen) = 0.028 It is better, than ,  size of tower (0.087 x0.087)

  34. CMS coverage

  35. Finding charged tracks Efficiency and fake rates • Occupancy in central Pb+Pb Event: • 1-3% in Pixel Layers • Up to 70% in Strip Layers @ dNdy 7000

  36. Fragmentation function for 100GeV Jets embedded in dN/dy ~5000 events. Use charged particles and electromagnetic clusters Jet fragmentation Longitudinal momentum fraction z along the thrust axis of a jet: pT relative to thrust axis: Using ECAL clusters~p0 in CMS

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