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US participation in Heavy Ion Physics with Compact Muon Solenoid at LHC

US participation in Heavy Ion Physics with Compact Muon Solenoid at LHC. MIT, Rice, TAMU, UC Davis, UC Riverside, UI Chicago, U Iowa.

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US participation in Heavy Ion Physics with Compact Muon Solenoid at LHC

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  1. US participation in Heavy Ion Physics with Compact Muon Solenoid at LHC MIT, Rice, TAMU, UC Davis, UC Riverside, UI Chicago, U Iowa M. Ballintijn,K Barish,R Betts, BE Bonner, W.Busza, D.Cebra, G.Eppley, E.Garcia, F.Geurts, C.Halliwell, D.Hofman, P.Kulinich, W.Llope, M.Murray, G. van Nieuwenhuizen, E.Norbeck, R.Nouicer, Y.Onel, C.Roland, G.Roland, R.Seto, G.S.F.Stephans, B. Wyslouch, P.Yepes CMS HI workshop was held at MIT February 2002

  2. US Heavy Ion physics today • RHIC has completed first long run of Au-Au at (sNN) =200 GeV/c (Its highest energy) • Expect to run for many years • It has reached design luminosity • Expect improvements • The four detectors: BRAHMS, PHENIX, PHOBOS and STAR • BRAHMS and PHOBOS have short lifetime (<4 y) • Much better detectors and running conditions than ever before in the field of relativistic heavy ions • Practically no involvement at LHC

  3. Main RHIC physics and tools • Equation of state of QCD: connection to lattice results predicting phase transitions • Chiral symmetry restoration • Quark Gluon Plasma, How does a high-temperature quark-gluon state emerge from the collision of nuclei? • Photon and di-lepton probes ( J/), studying effects of the plasma on particle production and survival • Production of high pt particles is affected by the energy loss in nuclear matter Early results are accumulating. No large, obvious effects seen, but some puzzles start to appear

  4. Integrated Au-Au luminosity PHENIX during last 10 days: 24 (mb)-1/week Lave(week) = 0.4  1026 cm-2 s-1 Lave(week)/Lave(store) = 27 % FY2001 – 02 100 GeV/amu FY2000 (66 GeV/amu)

  5. Multiplicity per nucleon-nucleon interaction as a function of collision energy for heavy ions and for proton-antiproton collisions

  6. Preliminary STAR Comparison of momentum spectra of particles AuAu vs ppToo few high pt particles ?

  7. Production of high pT particles, e.g. p0

  8. Heavy Ion physics at the LHCIncrease energy (sNN) 200->5500 GeV • Saturated gluon distributions in colliding nuclei, initial state of the system calculable in perturbative QCD • Plasma has higher temperature and lives longer in partonic state • Spectrum of quarkonia produced with high statistics • Jets clearly visible and identifiable • Z0 produced in large numbers HI group in CMS has produced many excellent physics studies Results need some update and extensions to take into account RHIC results

  9. The experiments ALICE: dedicated HI experiment ATLAS: pp experiment, recent HI interest CMS: pp experiment with HI program

  10. Design of LHC experiments is affected by the multiplicity of charged particles Extrapolated to LHC: dN/dh~1400 LHC? LHC detectors are being designed for dN/dy~8000 Peter Steinberg, 2002

  11. Quarkonia, CMS is very good here Detailed studies using full simulation, reconstruction, background subtraction dN/dy studied from 2500 to 8000 Very large event rate Uses muon detector, outer tracker, pixels J/  family Yield/month (kevents, 50% eff) ’/  ratioaffected by the initial conditions: a plasma thermometer(Ramona Vogt)

  12. Can we use tracker ? CMS Tracker Occupancy • Calculated for PbPb dNch/dy=5000 • For reference: STAR TPC occupancy reaches 22%

  13. Jet fragmentation • Find jets using calorimetry • Study charged particle momenta inside of a jet using the tracker • 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

  14. Global observables e.g. Et Field OFF Field ON Field OFF Field ON

  15. Our proposal to DoE/Nuclear • Extend the physics reach of the US heavy ion community beyond RHIC’s energy scale • Concentrate US physics effort on the study of phenomena most likely to be affected by the energy increase, the “hard probes”: • Quarkonia and heavy quark production • Jet production, jet-jet, jet-gamma and jet-Z0 correlations • Provide US/RHIC expertise and tools to study high pt processes in AA collisions at the LHC • Use detector designed for high pt physics: CMS • LHC starts in mid-2007 with pp, AA to follow in 2008(?): Be ready with strong group in 2008

  16. Our proposal to DoE/NuclearSpecific plans of the existing groups • Physics studies, software development • High Level Trigger code development + request to fund 2/8 slices of Event Filter Farm (Rice, MIT, UC Davis, UCR) • Zero degree calorimeter (U Iowa, UIC, TAMU) • Total ~ 5 M$ from DoE/Nuclear • review took place 2&3 of April @ DoE, no final report yet. Closeout conclusion: “continue studies, come back later” • competing with ALICE and ATLAS(!)

  17. Centrality: Participants vs. Spectators The collision geometry (i.e. the impact parameter) determines the number of nucleons that participate in the collision “Spectators” Only ZDCs measure Npart Zero-degreeCalorimeter “Spectators” • Many things scale with Npart: • Transverse Energy • Particle Multiplicity • Particle Spectra “Participants” Detectors at 90o

  18. PAIR OF PANTS (POP) Zero Degree Calorimetry for CMS • Beam pipe splits 140m from IR. BEAM ZDC LOCATION ALIGNMENT PINS BEAM INNER WALL Z-AXIS

  19. RHIC ZDCs work very well

  20. 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

  21. AA Event Size & Data Flow Event Size

  22. L1 HLT Data Flow and Rates HLT better trigger job

  23. Moore’s Law: double/18 months for ~8 years CPU Estimate of HI Online Tracking • Use STAR (Rice) experience • Scale linearly with # clusters from STAR AuAu to CMS PbPb • Assume Moore’s Law June 16, 2000 First STAR event tracked on line

  24. Near term plan • Work together with heavy ion group in CMS on expanding the physics scope of the heavy ion program • Develop good physics case for tracking in CMS, at HLT level and in offline analysis • Develop and possibly prototype Zero degree calorimeter. • Fight for funding from DoE, expand collaboration

  25. Summary • CMS has a potential to be an excellent detector for heavy ion physics • RHIC results will really determine the scope of interesting physics, the US community will have direct access to the RHIC experience • HI physicists could provide useful expertise, manpower and source of funding

  26. Z0 production • Z0-mm can be reconstructed with high efficiency • A probe to study nuclear shadowing and parton energy loss • Z0 alsoproposed as reference to  production. • Nuclear effects may depend on mass MZ>M • Different production mechanisms: • Z0: antiquark-quark, quark-gluon and antiquark-gluon. • : gluon-gluon.

  27. Open b: high mass m+m- : medium modification, energy loss for b-quarks Muon tracking (muon+tracker) Displaced vertices (pixels)

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