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

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 * in pp, in PbPb

5 LHC: Cross-sections and Rates Cross-sections of interesting probes expected to increase by factors ~ 10 ( cc ) to ~ 10 2 ( bb ) to ~ > 10 5 (very high p T jets) 

6 The LHC Ion Collider Running conditions for ‘typical’ Alice year: + other collision systems: pA, lighter ions (Sn, Kr, Ar, O) energies 5.5 TeV). Collision system pp PbPb √s NN (TeV) L 0 (cm -2 s -1 ) /L 0 (%) Run time (s/year) σ geom (b) * * * 7.7 * L max (ALICE) = ** Lint (ALICE) ~ 0.7 nb -1 /year

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

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

9 Inner Tracking System ITS 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 % X 0 Status: installed; being commissioned Posters by S. Moretto; G.J. Nooren

10 Inner Tracking System ~ 10 m 2 Si detectors, 6 layers Pixels, Drift, double sided Strips Strips SSD Drift SDD Pixels Inner Silicon Tracker Pixels SPD

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

12 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% X 0 total material for perpendicular tracks Drift gas:Ne (86) / CO 2 (9.5) / N 2 (4.5) + ~1ppm O 2 novel digital electronics (ALTRO) highly integrated, digital shaping; tail cancellation;0-suppression; Baseline restoration Powerful laser calibration system ALICE TPC

13 ALICE TPC: 5 years construction

14 Commissioning the TPC electronics

15 Cosmics recorded in 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 electron ID in central barrel p>1 GeV/c fast trigger for high momentum particles (hadrons, electrons) 540 detectors ~ 760m 2 18 super modules length: 7m X/X 0 ~ 22 % 28 m 3 Xe/CO 2 (85/15) 1.2 million channels Transition Radiation Detector (TRD) ‘Outer’ Central Detectors: TRD, TOF, HMPID, PHOS, EMCAL Status: partially installed; being commissioned Posters by R. Bailhache; K. Oyama

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 pads, 2.5*3.5 cm 2 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 Proximity Focused RICH 11 m 2 active detector area 7 modules - 0.6< η < 0.6; Δφ = 58 deg CsI Photocathode read by pads Threshold momentum = 1.21* (Particle Mass) PID optimization for 1 GeV < p < 6 GeV High Momentum Particle Identifier: HMPID Poster by L. Monar

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

23 PHOton Spectrometer: PHOS PbO 4 W- crystal calorimeter for Photons, neutral mesons, 1 to > 100GeV Crystals: 2.2*2.2 cm 2, 20 X 0, APD R/O Operated at – 25 deg; 5 pe / MeV σ(E) ≈ 3%; σ(x,y) ≈ 4 mm; σ(t) ≈ 1 ns; at 1GeV < 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 3 rd module during 2008; Ultimately 5 modules with crystals expected by 2010 Poster by Y. Kharlov

24 ElectroMagnetic Calorimeter: EMCAL 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 projective towers in ‘Shashlik’ geometry with APD R/O L0 trigger in < 900 ns for high-p T jets, photons, electrons Status: project approved in Dec of 12 supermodules early 2009

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

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 (K 0, K +, K -, Λ, D) K and L decays beyond 10 GeV/c leptons (e,μ ), photons, π 0 electrons TRD: p > 1 GeV/c, muons: p > 5 GeV/c, π 0 in PHOS: 1 < p < 80 GeV/c excellent particle ID up to ~ 50 to 60 GeV/c

27 Conceptual Layout of Muon Spectrometer Absorber Tracking chambers Trigger stations Trigger p t cut on single m: ● Low (~1 GeV/c) ● High (~2 Gev/c) Acceptance on single m: ● p>4 GeV/c ● < η < ΔM/M ~ 1% at Υ- mass Dipole

28 Muon Spectrometer: Instrumentation 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* 10 6 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) Status: installed; being commissioned Talk by B. Espagnon

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

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 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 m from IP; to measure spectators; 2 em calorimeters at -7m Quartz fibre technology V0-A during assembly Proton ZDC Posters by N. de Marco; T. Malkiewicz FMD3 installed

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

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 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 1 st global Commissioning Run systematic reconstruction of all RAW data Reconstructed events made available to collaboration Accumulated data Talk by F. Carminati GRID operation during December Run In 2007: 65 Sites on 4 continents 7500 CPUs 1PB of storage Europe Asia North America Africa

36 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 Start-up Configuration: April 2008

37 ALICE has momentum coverage from 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 = 3·10 30 cm -2 s -1 x 10 7 s = 30 pb -1 N(min. bias) > 10 8 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 pp Physics with ALICE 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-diffractive events Posters by J. Grosse-Oetringhaus, R. Lietava; T. Malkiewicz; R. Wan

39 Initial Strange Particle Studies based on Pythia for LHC significant samples of strange particles in < 100 million minimum bias events: K 0 : 7x10 6 Λ : 10 6 Ξ : 2x10 4 Ω : 270 detailed study of flavour composition  *(1520) -> pK Poster by O. Villalobos

40 Heavy Flavor Measurements D 0 → K + π from sec. vertices B → e + X sensitivity to range of pQCD predictions (based on 10 9 events) Talk by M. Masera σ(vertex) = 50 μm at 1.5 GeV/c

41 Heavy Flavor in Muon Channel J/ Ψ; Υ → μ μ; < y < Initial sample of 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) 507 B.Z. Kopeliovich and B. Zakharov, Z. Phys. C43 (1989) 241  Poster by M. Oldenburg

43 Fully commissioned Detector and Trigger Reference data, alignment, calibration from pp run 1/20 of nominal luminosity during one month ∫Ldt = 5·10 25 cm-2 s -1 x 10 6 s = 0.05 nb -1 for PbPb at 5.5 TeV PbPb minbias = 10 7 events; PbPb central = 10 7 events First 10 5 events: global event properties multiplicity; η - density; elliptic flow First 10 6 events: source characteristics Particle spectra; resonances; differential flow; interferometry First 10 7 events: Bulk Properties of medium Jet quenching; Heavy Flavor production; Charmonia ‘First Three Minutes’ Heavy Ion Physics Talks by M. Masera, A. Morsch, S. Raniwala, K. Safarik Posters by N. de Marco; F. Noferini; N. van der Kolk; E. Scomparin

44 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% accepted jets/month jets/event Pb+Pb p t jet > (GeV/c) Talk by A. Morsch q ^

45 R AA Heavy Flavor quenching: D, B, R AA Probes colour charge dependenceProbes mass dependence One year at nominal luminosity: 10 9 pp events; 10 7 central PbPb events

46 Di-Muon mass spectrum One Month (10 6 sec) Pb-Pb collisions at nominal luminosity Adequate statistics to study Υ- family and quench-scenarios J/Ψ ~ 3*10 5 Υ ~ 8000

47 J/Ψ ~ 3*10 5 Suppression vs recombination study suppression scenarios Quarkonia production Υ ~ 8000

48 Thermal and hard photons from QGP  all /  dec Posters by R. Diaz Valdes; Y. Karlov; Y. Mao

49 Measuring Thermal Photons from the QGP  all /  dec ALICE sensitivity to thermal radiation without and with quenching of the away jet, measured relative to all Gammas (basically gammas from π 0 ) Thermal photons above 3- 4 GeV expected to be measurable

50 Finally … ALICE is becoming reality after almost 15 years in the making 2 nd 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’

51 Alice: Getting ready…