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ALICE at LHC: getting ready for Physics

This presentation outlines the status of the ALICE experiment at the LHC, including the physics reach and challenges. It discusses the expected increase in plasma energy density, the extension of the low-x frontier, and the increase in cross-sections of interesting probes. The presentation also covers the inner tracking system, the TPC, and the outer central detectors such as the TRD, TOF, HMPID, PHOS, and EMCAL.

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ALICE at LHC: getting ready for Physics

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  1. ALICE at LHC:getting ready for Physics Christian W. Fabjan, CERN for the ALICE Collaboration Quark Matter 2008, Jaipur 9.2.2008

  2. Outline • Relativistic Ion Physics at LHC • Status of the Alice Experiment • Early days pp and ion physics • Physics Reach: a few challenging studies

  3. LHC: Plasma Energy Density; Lifetime Energy density expected to increase by factor ~ 2 – 3 Lifetime of QGP by Factor ~ 2 – 3

  4. LHC: extending the low-x Reach RHIC as opened the low-x frontier finding indications for new physics (CGC ?) LHC will lower the x- frontier by another factor 30 Can reach x = 3 * 10-6 in pp, 10-5 in PbPb

  5. LHC: Cross-sections and Rates Cross-sections of interesting probes expected to increase by factors ~ 10 ( cc ) to ~ 102 ( bb ) to ~ > 105(very high pT jets)

  6. The LHC Ion Collider √sNN (TeV) L0 (cm-2s-1) <L>/L0 (%) Run time (s/year) σgeom (b) Collision system pp 14.0 1031* 107 0.07 5.5 1027 70-50 106 * * 7.7 PbPb * Lmax (ALICE) = 1031 ** Lint (ALICE) ~ 0.7 nb-1/year Running conditions for ‘typical’ Alice year: + other collision systems: pA, lighter ions (Sn, Kr, Ar, O) energies (pp @ 5.5 TeV).

  7. ALICE Collaboration > 1000 Members (63% from CERN MS) ~ 30 Countries ~ 100 Institutes India Alice : collaboration of Nuclear and Particle Physicists with strong engineering and industrial participation

  8. ALICE: A Large Ion Collider Experiment at CERN-LHC Size: 16 x 26 meters Weight: 10,000 tonnes

  9. Inner Tracking System ITS Status: installed; being commissioned • Three different Silicon detector technologies; two layers each • Pixels (SPD), Drift (SDD), Strips (SSD) • Δ(rφ) resolution: 12 (SPD), 38 (SDD), 20 (SSD) μm • Total material traversed at perpendicular incidence: 7 % X0 Posters by S. Moretto; G.J. Nooren

  10. Inner Silicon Tracker Inner Tracking System ~ 10 m2 Si detectors, 6 layers Pixels, Drift, double sided Strips Pixels SPD Pixels Drift SDD Strips SSD

  11. ITS Russian Dolls - Sliding the SSD/SDD over the SPD TPC SPD SSD/SDD J.P. Wessels - First Physics with ALICE

  12. ALICE TPC • Optimized for dN/dη ≈ 8000 • l = 5 m, Ø = 5.6m, 88 m3, 570 k channels, • up to 80 Mbytes/event (after 0 suppression) • Features: • lightweight: 3% X0 total material for perpendicular tracks • Drift gas:Ne (86) / CO2 (9.5) / N2(4.5) + ~1ppm O2 • novel digital electronics (ALTRO) • highly integrated, digital shaping; tail cancellation;0-suppression; Baseline restoration • Powerful laser calibration system

  13. RODS OROCs ENDPLATE IROCs ALICE TPC: 5 years construction

  14. Commissioning the TPC electronics

  15. Cosmics recorded in TPC@ALICE Commissioning with Cosmics and Laser tracks Spatial resolution and Electronics noise in experiment according to specifications σ(dE/dx) ≈ 5.5 to 6.5 %, depending on multiplicity (measurements and simulations) Status: installed; being commissioned

  16. ‘Outer’ Central Detectors: TRD, TOF, HMPID, PHOS, EMCAL Transition Radiation Detector (TRD) • electron ID in central barrel p>1 GeV/c • fast trigger for high momentum particles (hadrons, electrons) • 540 detectors ~ 760m2 • 18 super modules • length: 7m • X/X0 ~ 22 % • 28 m3 Xe/CO2 (85/15) • 1.2 million channels Posters by R. Bailhache; K. Oyama Status: partially installed; being commissioned

  17. TRD - Signal Generation & Processing

  18. TRD Installation

  19. Time of Flight: TOF • TOF: Timing, Triggering, PID • Δη = 1.70; Δφ = 2π; • 18 ‘Supermodules’ • Requirement: σ≈ 50 ps • Multi-gap Resistive Plate Chambers: MRPC’s • 10 gaps; 250 μm thick • Readout organized in 160 000 pads, 2.5*3.5 cm2 • Optimization possible, because we finally understand them… • A revolution in TOF PID Timing Resolution σ≈ 50 ps Poster by A. Alici

  20. TOF: installation finished 04/08; being commissioned

  21. High Momentum Particle Identifier: HMPID • Proximity Focused RICH • 11 m2 active detector area • 7 modules • - 0.6< η < 0.6; Δφ = 58 deg • CsI Photocathode read by 16100 pads • Threshold momentum = 1.21* (Particle Mass) • PID optimization for • 1 GeV < p < 6 GeV Poster by L. Monar

  22. HMPID: Installed; being commissioned HMPID (Sept ’06)

  23. PHOton Spectrometer: PHOS • PbO4W- crystal calorimeter for Photons, neutral mesons, 1 to > 100GeV • Crystals: 2.2*2.2 cm2 , 20 X0, APD R/O Operated at – 25 deg; 5 pe / MeV • σ(E) ≈ 3%; σ(x,y) ≈ 4 mm; σ(t) ≈ 1 ns; at 1GeV • - 0.12 < η < 0.12; Δφ = 100 deg; at R = 460 cm • L0 trigger available at < 900 ns • Module tested, calibrated in test beam; 1 or 2 modules to be installed in 04/08 • 3rd module during 2008; • Ultimately 5 modules with 18 000 crystals expected by 2010 Poster by Y. Kharlov

  24. ElectroMagnetic Calorimeter: EMCAL Status: project approved in Dec 2007 2 of 12 supermodules early 2009 • Pb-Scintillator em calorimeter for • Jet physics in conjunction with tracking and PID • Approximately opposite to PHOS • -0.7 <η < 0.7; Δφ = 107 deg • EM resolution σ(E) < 0.1/√E • 13 000 projective towers in ‘Shashlik’ geometry with APD R/O • L0 trigger in < 900 ns for high-pT jets, photons, electrons

  25. ALICE Tracking Performance TPC acceptance = 90% Momentum resolution ~ 5% @ 100 GeV Robust, redundant tracking from < 100 MeV/c to > 100 GeV/c Very little dependence on dN/dy up to dN/dy ≈ 8000 dNch/dy=6000 drop due to proton absorption Posters by P. Christiansen; R. Wan p/p < 5% at 100 GeV with careful control of systematics

  26. Particle Identification in ALICE • ‘stable’ hadrons (π, K, p): 100 MeV/c < p < 5 GeV/c; (π and p with ~ 80 % purity to ~ 60 GeV/c) • dE/dx in silicon (ITS) and gas (TPC) + time-of-flight (TOF) + Cherenkov (RICH) • decay topologies (K0, K+, K-, Λ, D) • K and L decays beyond 10 GeV/c • leptons (e,μ ), photons, π0 • electrons TRD: p > 1 GeV/c, muons: p > 5 GeV/c, π0 in PHOS: 1 < p < 80 GeV/c • excellent particle ID up to ~ 50 to 60 GeV/c

  27. Absorber Tracking chambers Conceptual Layout of Muon Spectrometer Trigger stations Dipole 8 Acceptance on single m: • p>4 GeV/c • - 4.0 < η< - 2.5 0 Trigger pt cut on single m: • Low (~1 GeV/c) • High (~2 Gev/c) ΔM/M ~ 1% at Υ- mass 5 10 15 8 20

  28. Muon Spectrometer: Instrumentation Status: installed; being commissioned Talk by B. Espagnon • Tracking • 5 tracking stations with two planes each • Cathode pad chamber technology with 60 μm space resolution; • Electronics: preamp/shaper ASIC (‘MANAS’), designed and developed in India; total of 1.1* 106 channels • MANAS: first, large-scale production of a mixed-signal ASIC in India • Triggering • 2 Trigger stations with two planes each • RPC technology; operation in proportional or limited streamer mode • Dual threshold discriminator for optimum timing (σ< 2ns)

  29. Steel cone from Finland Tungsten fromChina Building the ‘mundane’ Muon Absorber Graphite & Steel from India Lead from England Concrete from France, Engineering & Supervision by CERN Design by Russia (Sarov/ISTC) Italianpolyethylene

  30. Partial view of Muon chambers

  31. Muon Spectrometer: Indian Flavor The Indian team had the privilege to build the largest units of the Tracking chambers

  32. ‘Forward Detectors’:FMD, T0, V0, ZDC, PMD FMD3 installed Posters by N. de Marco; T. Malkiewicz • FMD: Forward multiplicity detector • 3 planes of Si-pad detectors covering -3.4 < η < - 1.7; 1.7 < η < 5.0 • T0: 2 arrays of 12 quartz Cherenkov counters • Time reference for TOF; vertex measurement; 30 ps resolution • V0: 2 arrays of 32 scintillator tiles • trigger on centrality, luminosity monitor, beam-gas rejection; 0.6 ns resolution • ZDCs: 2 neutron and proton calorimeters at +- 116 m from IP; to measure spectators; 2 em calorimeters at -7m • Quartz fibre technology V0-A during assembly Proton ZDC

  33. PMD: Photon Multiplicity Detector Poster by T. Nayak PMD modules after assembly at Kolkata Lead converter installed • Pre-shower detector for photon multiplicity • 6mm diameter hexagonal cells • Total of 220 000 channels covering 2.3 < η < 3.7 • Readout adopted from Muon tracking, using MANAS chip • All-Indian responsibility

  34. Managing the Data: Trigger, HLT, DCS, DAQ, ECS • Central Trigger Processor (CTP) • Hierarchy of three Levels ( L0, L1, L2 ) • High-Level Trigger (HLT) : 1000 processors; scaleable to 20 000 • sharpened trigger decisions; data pre-processing and compression; • Detector Control System (DCS) • Data Acquisition (DAQ): Bandwidth 500MBytes/ s; planned: 1.2 GBytes/s (following Luminosity increase) • Experimental Control System (ECS) • top layer; interface to experiment operation • Raw Data rate / year : 2.5 PByte Status: all systems installed; operational, commissioning continuing Poster by O. Villalobos

  35. Off-line Data processing 18TB Dec 2007: Data Processing during 1st global Commissioning Run systematic reconstruction of all RAW data Reconstructed events made available to collaboration Accumulated data • In 2007: • 65 Sites on 4 continents • 7500 CPUs • 1PB of storage Europe Africa Asia GRID operation during December Run NorthAmerica Talk by F. Carminati

  36. Start-up Configuration: April 2008 • Complete - fully installed & commissioned • ITS, TPC, TOF, HMPID, MUONS, PMD, V0, T0, FMD, ZDC, ACORDE, TRIGGER, DAQ • Partially completed • TRD (20%) to be completed by 2009 • PHOS (40%) to be completed by 2010 • EMCAL (0%) to be completed by 2010/11 • At start-up full hadron and muon capabilities • Partial electron and photon capabilities

  37. pp Physics with ALICE • ALICE has • momentum coverage from < 100 MeV/c to > 100 GeV/c • Excellent particle identification • At start-up • Possibly, short run at 900 GeV -> compare to known physics • At nominal energy: • ‘Alice’ luminosity ∫Ldt = 3·1030 cm-2 s-1 x 107 s = 30 pb-1 • N(min. bias) > 108 events ; few to 20 event-pile-up in TPC • Muon trigger at < 1 kHz • Electron trigger ~ few Hz • Needed reference data for heavy ion program • Multiplicity distributions • Measurement of strange, charm, beauty, quarkonia cross-sections • Baryon Transport Talk by K. Safarik Poster by R. Lietava

  38. Charged Particle Acceptance • operating with fast multiplicity trigger L0 from Silicon Pixels • efficiency studied for- single diffractive- double diffractive- non-diffractiveevents Posters by J. Grosse-Oetringhaus, R. Lietava; T. Malkiewicz; R. Wan

  39. p 0 K p s ´ yield p er – 5 0.1 0.01 10 0.4 0.4 – 4 2 10 e v ent statisti c s 4 4 4 4 4 104 10 10 10 10 10 n e e de d pp e v ents 5 6 8 9 4 4 10 10 10 10 10 10 n e e de d L*(1520) -> pK Initial Strange Particle Studies • based on Pythia for LHC • significant samples of strange particles in < 100 millionminimum bias events: • K0 : 7x106 • Λ : 106 • Ξ : 2x104 • Ω : 270 • detailed study of flavour composition Poster by O. Villalobos

  40. Heavy Flavor Measurements • D0→ K + πfrom sec. vertices • B → e + X σ(vertex) = 50 μm at 1.5 GeV/c • sensitivity to range of pQCD predictions • (based on 109 events) Talk by M. Masera

  41. Heavy Flavor in Muon Channel • J/ Ψ; Υ→μμ; - 4.0 < y < - 2.5 • Initial sample of 60000 J/y and 2000  sufficient to measure production cross-sections

  42. Baryon Transport • Discriminate between two competing processes • Baryon number transport via quark exchange • Baryon number transport via ‘Baryon junction’ • With measurement of asymmetry A • Systematic errors: < 1% for p < .5 GeV/c • Experimental handles: • Study over large rapidity gap; • at LHC : Δη > 9 units • Study as function of multiplicity G.C. Rossi and G. Veneziano, Nucl. Phys B123 (1977) 507B.Z. Kopeliovich and B. Zakharov, Z. Phys. C43 (1989) 241  Poster by M. Oldenburg

  43. ‘First Three Minutes’ Heavy Ion Physics • Fully commissioned Detector and Trigger • Reference data, alignment, calibration from pp run • 1/20 of nominal luminosity during one month • ∫Ldt = 5·1025 cm-2 s-1 x 106 s = 0.05 nb-1 for PbPb at 5.5 TeV • PbPbminbias = 107 events; PbPbcentral = 107 events • First 105 events: global event properties • multiplicity; η - density; elliptic flow • First 106 events: source characteristics • Particle spectra; resonances; differential flow; interferometry • First 107 events: Bulk Properties of medium • Jet quenching; Heavy Flavor production; Charmonia Talks by M. Masera, A. Morsch, S. Raniwala, K. Safarik Posters by N. de Marco; F. Noferini; N. van der Kolk; E. Scomparin

  44. pt jet > (GeV/c) jets/event Pb+Pb accepted jets/month ^ 5 3.5 102 4.9 1010 q 50 7.7 10-2 1.5 107 100 3.5 10-3 8.1 105 150 4.8 10-4 1.2 105 200 1.1 10-4 2.8 104 Jet Production at LHC • Initial measurements up to 100 GeV (untriggered charged jets only) • Detailed study of fragmentation possible • Sensitive to energy loss mechanism • Accuracy on transport coefficient <> ~20% Talk by A. Morsch

  45. Heavy Flavor quenching: D, B, RAA One year at nominal luminosity: 109 pp events;107 central PbPb events Probes colour charge dependence Probes mass dependence

  46. Di-Muon mass spectrum • One Month (106sec) Pb-Pb collisions at nominal luminosity • Adequate statistics to study Υ- family and quench-scenarios J/Ψ ~ 3*105 Υ ~ 8000

  47. Quarkonia production Υ ~ 8000 • J/Ψ ~ 3*105 • Suppression vs recombination study suppression scenarios

  48. gall/gdec Thermal and hard photons from QGP Posters by R. Diaz Valdes; Y. Karlov; Y. Mao

  49. gall/gdec gall/gdec Measuring Thermal Photons from the QGP ALICE sensitivity to thermal radiation without and with quenching of the away jet, measured relative to all Gammas (basically gammas from π0 ) Thermal photons above 3- 4 GeV expected to be measurable

  50. Finally … • ALICE is becoming reality after almost 15 years in the making • 2nd Commissioning run to start next week, Feb11th for four weeks • Installation will be terminated in April • Further commissioning running until first beams, scheduled for summer 2008 • All systems on track for taking first pp collisions • ALICE is the general purpose Heavy Ion experiment, designed to address the very rich, expected physics program; • It is versatile enough to address the ‘Unknown’

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