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The LHC Heavy Ion Experiments: Overview, Program, and Physics Potential

This outline provides an overview of the LHC heavy ion program, including the properties of heavy ion collisions in the LHC regime, the detectors used in the experiments (ALICE, ATLAS, CMS), and the physics potential of studying jets, quarkonia, direct photons, and heavy quarks. It also highlights the participants involved and the running parameters of the LHC as a heavy ion collider.

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The LHC Heavy Ion Experiments: Overview, Program, and Physics Potential

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  1. The LHC Heavy Ion Experiments OUTLINE • Overview • Program • The LHC as Heavy-Ion Collider • Properties in the LHC regime • The LHC and the Detectors • LHC • ALICE • ATLAS • CMS • The Physics potential • Jets and jet suppression • Quarkonia • Direct photons • Heavy quarks Quark Matter 05 August 8, 2005

  2. The LHC Heavy Ion Program • ~ 1100 participants • ALICE ~ 1000 • ATLAS ~ 30 • CMS ~ 100 A large community which has been constantly growing over the years, and still grows => VERY lively field • 11 experimental contributions to QM’05 • 4 oral: P.Crochet, K. Gulbrandsen, M.J. Murray, P. Nevski. • 7 posters: C.H. Christensen, A. Dainese, D. Elia, H.M. Gray, • T.K. Nayak, B. Pastircak, G. Renault. Quark Matter 05 August 8, 2005

  3. 5.5 1027 70-50 106 ** 7.7 LHC as Heavy-Ion Collider Running parameters: √sNN (TeV) L0 (cm-2s-1) <L>/L0 (%) Run time (s/year) sgeom (b) Collision system 1034 * 14.0 107 0.07 pp PbPb *Lmax(ALICE)= 1031 ** Lint(ALICE) ~ 0.7 nb-1/year Other collision systems: pA, lighter ions (Sn, Kr, Ar, O) and energies Quark Matter 05 August 8, 2005

  4. Properties in the LHC regime • Initial condition different than at RHIC • Higher density • Bigger system • Hotter system • Longer lived • Dominated by hard processes • Jets • Heavy Quarks • Soft and intermediate pt observables of importance • as seen at RHIC • v2 measurements Quark Matter 05 August 8, 2005

  5. 5 15.0 10.0 Nch/(0.5Npart) dNch/dh|h<1 103 5.0 5 1.0 2 10 102 103 102 103 104 √s (GeV) hep-ph0104010 What multiplicity to expect at LHC dNch/dh ~ 2500 dNch/dh ~ 1500 • Large uncertainty in extrapolation from RHIC data to LHC • Expected multiplicity in the range 1500 to 6000 charged particles per unit rapidity • ALICE is optimized for 4000 charged particles and checked up to 8000 charged • particles per unit rapidity • CMS & ATLAS (checked up to 7000) will provide good performances over the • expectedrange. Quark Matter 05 August 8, 2005

  6. 108 106 104 102 100 Q2 (GeV2) 10-6 10-4 10-2 100 x A new kinematic regime • Probe initial partonic state in a new Bjorken-x range (10-3 - 10-5): • nuclear shadowing, • high-density saturated gluon • distribution. • Larger saturation scale (QS=0.2A1/6 √sδ= 2.7 GeV): particle production dominated by the saturation region. Quark Matter 05 August 8, 2005

  7. (h++h-)/2 p0 √s = 5500 GeV 200 GeV LO p+p y=0 17 GeV LHC RHIC SPS Hard processes • At LHC hard processes contribute • significantly to the total AA cross-section. • Bulk properties are dominated by • hard processes • Very hard probes are abundantly • produced. • Hard processes are • extremely useful tools. • Probe matter at very early • times. • Hard processes can be • calculated by pQCD Heavy quarks and weakly interacting probes become accessible Quark Matter 05 August 8, 2005

  8. One dedicated HI experiment: ALICE Two pp experiments with HI program: ATLAS and CMS Quark Matter 05 August 8, 2005

  9. LHC status • Main objectives: • terminate installation in Febr. 2007 • first pp collisions in summer 2007 • first long heavy ion run end of 2008 • The industrial production of standard • components is compatible with these objectives. • The ramping up of QRL activities and magnet • installation is critical to maintain this schedule. Quark Matter 05 August 8, 2005

  10. Solenoid magnet 0.5 T Cosmic rays trigger ALICE: the dedicated HI experiment • Forward detectors: • PMD • FMD, T0, V0, ZDC • Specialized detectors: • HMPID • PHOS • Central tracking system: • ITS • TPC • TRD • TOF • MUON Spectrometer: • absorbers • tracking stations • trigger chambers • dipole Quark Matter 05 August 8, 2005

  11. Inside the Solenoid for the central detectors; L3 legacy of LEP Quark Matter 05 August 8, 2005

  12. Hybrid bonding on K&S manual bonder Pixel ITS modules • Now being produced in series…. Drift Strip Quark Matter 05 August 8, 2005

  13. The TPC TPC Tracking, dE/dx -0.9<<0.9 Readout chamber installation tool Inside the TPC Readout chamber Field Cage Quark Matter 05 August 8, 2005

  14. TPC-ITS Integration Test Quark Matter 05 August 8, 2005

  15. ALICE: The dedicated HI experiment • ALICE will meet the challenge to measure flavor content and phase-space distribution event-by-event: • Most (2p * 1.8 units h) of the hadrons(dE/dx + TOF),leptons(dE/dx, transition radiation, magnetic analysis)and photons(high resolution EM calorimetry). • Track and identify from very lowpt (< 100 MeV/c; soft processes)up to very high pt(>100 GeV/c; hard processes). • Identify short lived particles(hyperons, D/B meson)through • secondary vertex detection. • Identify jets. Quark Matter 05 August 8, 2005

  16. Particle Identification in ALICE p, K, p identified in large acceptance (2p * 1.8 units h) via a combination of dE/dx in Si and TPC and TOF from ~100 MeV/c to 2 (p/K) - 3.5 (K/p) GeV/c Electrons identified from 100 MeV/c to 100 GeV/c (with varying efficiency) combining Si+TPC+TOF with a dedicated TRD In small acceptance HMPID extends PID to ~5 GeV/c Photons measured with high resolution in PHOS, counting in PMD and EM energy flow in EMCAL p/K TPC + ITS (dE/dx) K/p e /p p/K e /p TOF Alice uses ~all known techniques! K/p p/K HMPID (RICH) K/p 0 1 2 3 4 5 p (GeV/c) TRDe /p PHOSg /p0 EMCAL 1 10 100 p (GeV/c) Quark Matter 05 August 8, 2005

  17. ALICE Tracking Combined tracking efficiency and momentum resolution Quark Matter 05 August 8, 2005

  18. CMS as a Detector for Heavy-Ion Physics • DAQ and Trigger • High rate capability for A+A, p+A, p+p • High Level Trigger capable of full reconstruction of most HI events in real time • Fine Grained High Resolution Calorimeter • Hermetic coverage up to |h|<5 • (|h|<7 proposed using CASTOR) • Zero Degree Calorimeter (proposed) • Tracking m from Z0, J/, • Wide rapidity range |h|<2.4 • σm ~50 MeV at  • Silicon Tracker • Good efficiency and low fake rate for pT>1 GeV • Pixel occupancy at 1-2% level even in Pb+Pb • Excellent momentum resolution Dp/p~2% for pT<25 GeV and higher m chambers Fully functional at highest expected multiplicities Detailed studies at ~dNch/dh ~3000-5000 and cross-checks at 7000-8000 ECAL Si Tracker including Pixels HCAL Quark Matter 05 August 8, 2005

  19. CMS under construction Magnet & Muon Absorber Hadron Calorimeter Electromagnetic Calorimeter DAQ Si tracker & Pixels Quark Matter 05 August 8, 2005

  20. The ATLAS Detector • Excellent Calorimetry • Hermetic coverage up to || < 4.9 • Fine granularity (with longitudinal segmentation) • Very good jet resolution Length • Inner Detector (Si pixel and SCT) • Large coverage up to || < 2.5 • High granularity pixel and strip detectors • Good momentum resolution • Large Acceptance m spectrometer • Coverage up to || < 2.7 Quark Matter 05 August 8, 2005

  21. ATLAS under construction LAr calorimeter Muon chamber installation Toroid installation Pixel disc Quark Matter 05 August 8, 2005

  22. CMS & ATLAS • Experiments designed for high pt physics in pp collisions: • Precise tracking systems in a large solenoid magnetic field; • Hermetic calorimeters (EM+Hadronic) systems with fine grain segmentation; • Large acceptance muon spectrometers; • Accurate measurement of high energy leptons, photons and hadronic jets. • Provide adequate performances for selected high pt (> 1 GeV/c) probes for HI physics. Quark Matter 05 August 8, 2005

  23. pt coverage of the three experiments 0 1 2 10 100 T=LQCD Qs pt (GeV/c) Hard processes modified by the medium Bulk properties ALICE PID CMS&ATLAS Quark Matter 05 August 8, 2005

  24. Hard processes modified by the medium • Jets : • reflect interactions of partons in partonic matter. Jets are copiously • produced. Typical rates are 100/event at 2 GeV, 1/event at 20 GeV and • 100k/month above 150 GeV. • Effects: • reduction of single inclusive high pt particles and modification of the jet • fragmentation function. Parton specific and Flavour specific. • Jet fragmentation and shape: • distance R to leading particle • pT of particles for R < Rmax • Multiplicity of particles for R < Rmax • Heating: kT = p  sin((particle, jet axis)) • Forward backward correlation: (particle, jet axis) • Fragmentation function: F(z)=1/NjdNch/dz z=pt/pjet • Experimental Consequences: • Measurement of Jet Energy is important • Requires good momentum analysis from ~ 1GeV/c to ~100 GeV/c • Requires high quality tracking and PID down to low pt Dissolution of o’nium bound states Quark Matter 05 August 8, 2005

  25. Jet Reconstruction in CMS and ATLAS CMS ATLAS Pb-Pb collisions (b= 0 –1 fm Efficiency Fake rate Pb-Pb Energy resolution p-p For ET > 75GeV: efficiency > 95%, fake < 5% Good energy and angular resolution Next: use tracking information to lower the threshold and reduce the fakes Quark Matter 05 August 8, 2005

  26. Unquenched Quenched (AliPythia) Quenched (Pyquen) Unquenched Quenched (AliPythia) Quenched (Pyquen) Fragmentation functions ALICE CMS z pjet kT High precision tracking over large range in momenta will allow for detailed jet shape analysis to study the energy loss mechanism Quark Matter 05 August 8, 2005

  27. Quarkonia in ALICE U m+m- J/y m+m- Rate/month ~ 100k ~ 70 MeV resolution Rate/month ~15k ~ 130 MeV resolution Quark Matter 05 August 8, 2005

  28. Quarkonia in CMS and ATLAS CMS J/y m+m- J/  family ATLAS U m+m- Rate/month ~ 100k ~ 50 MeV resolution sMY=50 MeV Expect ~24k J/y and ~ 18/5/3 k ,’,’’ After one month of Pb+Pb running at L=1027cm-2s-1 with 50% efficiency Rate/month ~ 10k ~ 120 MeV resolution Quark Matter 05 August 8, 2005

  29. Prompt Photon Spectrum (One Year of Running) Conclusion : high pT (>20 Gev/c) well within reach of Alice Quark Matter 05 August 8, 2005

  30. Photon tagged jet fragmentation function (1 STDY statistics) Hijing central + PYTHIA 22, Eg > 20 GeV RAA = FFAA/TABFFpp Fragmentation Function dN/dz ▫γ-jet ▪di jet z=pThadron/Eγ Medium effects measurable down to 5% at low z Quark Matter 05 August 8, 2005

  31. mc PDFs scales pp, 14 TeV down to 1 GeV/c! down ~ 0! Heavy Quarks: D0K-+ Quark Matter 05 August 8, 2005

  32. Looking forward to first operation • To a timely completion of LHC and experiments construction in April 2007: • Accelerators and experiments are in the production phase. • For an exciting decade of HI physics in a new regime of physics: • Detailed physics program is taking shape ( Physics Performance Reports, Yellow Report,..) • The 2005 – 2007 challenge: • Keep the detector construction on its rather tight time scale • Continue preparation and bring to ready-state the physics analysis program. Thanks to Bolek Wyslouch and Pavel Nevski for providing material for ATLAS and CMS Quark Matter 05 August 8, 2005

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