Rencontres de Moriond QCD and Hadronic Interactions La Thuile, 23 rd March 2007 Chiara Zampolli Heavy Ion Physics with the ALICE Experiment at LHC –The ALICE LHC –Selected Topics: –Open Charm and Open Beauty –Quarkonia –Jet Physics –ALICE First Day Physics –Conclusions Chiara Zampolli for ALICE Collaboration Museo Storico della Fisica e Centro Studi e Ricerche E. Fermi & INFN

23 rd March 2007, Moriond QCDChiara Zampolli 2 LHC Experiments ATLAS CMS Designed for high p T physics in p-p collisions ALICE Dedicated LHC HI experiment ~ 9 km CERN LHC

23 rd March 2007, Moriond QCDChiara Zampolli 3 LHC Running Conditions Collision system √s NN (TeV) L 0 (cm -2 s -1 ) Run time (s/year)  geom (b) pp PbPb …Other scenarios (lighter ions, different √s NN )… ALICE max L = 10 31SPSRHICLHC  0 QGP (fm/c) T/T c  (GeV/fm 3 )  QGP (fm/c) ≤22-4 ≥10 V f (fm 3 ) few 10 3 few 10 4 few 10 5 Collision system √s NN (TeV) L 0 (cm -2 s -1 ) Run time (s/year)  geom (b) PbPb Heavy Ion Program LHC hotter, denser, longer, bigger

23 rd March 2007, Moriond QCDChiara Zampolli 4 The ALICE Experiment TRD TOF HMPID PMD PHOS TPC Muon Arm ITS ALICE Set-up

23 rd March 2007, Moriond QCDChiara Zampolli 5 An ALICE PbPb Event p T > 1 GeV

23 rd March 2007, Moriond QCDChiara Zampolli 6 ALICE Heavy Ion Physics Programme Global Characteristics of the event Global Characteristics of the event –multiplicites, η distributions Degrees of freedom as a function of T Degrees of freedom as a function of T –hadron ratios and spectra, dilepton continuum, direct photons Collective effects Collective effects –elliptic flow Energy loss of partons in the QGP Energy loss of partons in the QGP –jet quenching, high p T spectrum, open charm and beauty Deconfinement Deconfinement –charmonium and bottomonium Chiral symmetry restauration Chiral symmetry restauration –Neutral to charged ratios, resonance decays Fluctuations and critical behaviour Fluctuations and critical behaviour –E-by-E particle composition and spectra Geometry of the emitting source Geometry of the emitting source –HBT, zero degree energy flow Various experimental techniques

23 rd March 2007, Moriond QCDChiara Zampolli 7 Open Charm and Open Beauty – Why? To provide constraints on parton energy loss (and more - nuclear shadowing, dead-cone effect...), since they are produced at the very early stage of the collision. To investigate heavy-quark propagation and hadronization. Baseline for quarkonia studies. charged hadrons From A. Mischke, 17/02/07 (Big Sky, Montana) Non photonic electron spectra:

23 rd March 2007, Moriond QCDChiara Zampolli 8 Open Charm and Open Beauty – How? LHC heavy flavour ( cc, bb) rates LHC heavy flavour ( cc, bb) rates system NN x-sect (mb) shadowing total multiplicity pp 14 TeV 11.2 / / / PbPb 5.5 TeV (5% centr) 6.6 / / / 4.6 PbPb, 5.5 TeV pp, 5.5 TeV PbPb, 5.5 TeV pp, 5.5 TeV PbPb/pp cc bb ALICE acceptance ALICE acceptance gg  (leading order) √s NN = 5.5 TeV x 1,x 2 = g mom fraction Central barrel, |η| < 0.9 Muon arm, 2.5 < η < 4 = 2.4 GeV, c = 9 GeV, b

23 rd March 2007, Moriond QCDChiara Zampolli 9 D 0  K -  + : ingredients ITS: impact parameter measurement ITS resolution 0.6 GeV/c TPC: tracking and momentum measurement TOF: Particle Identification

23 rd March 2007, Moriond QCDChiara Zampolli 10 D 0  K -  + : performance 10 7 Pb Pb √s NN = 5.5 TeV ( ~ 1 month data taking) S/B ≈ 10% Statistical significance S/√(S+B) ≈ 40 Performance in pp similar, even if worse primary vertex reconstruction (because of luminosity) – using e-by-e reconstructed vertex Similar performance in pPb K  invariant mass, PbPb Moreover... Study of quenching of charm and massless partons ( (p T ), ) for open beauty see ALICE PPR Vol.2. J. Phys. G: Nucl. Part. Phys

23 rd March 2007, Moriond QCDChiara Zampolli 11 Quarkonia (S = measured / expected yields) PLB (2006) To probe the nature of the medium the fireball created in the collision is made of. Sensitive to collision dynamics and to plasma formation. Dissociation points related to the temperature of the medium. SPS RHIC LHC ~ 30 Recombination? J/Ψ melting?

23 rd March 2007, Moriond QCDChiara Zampolli 12 Quarkonia in ALICE Measured both in the dielectron (midrapidity, TRD) and dimuon (forward rapidity, MUON) channel J/Ψ family  family M μμ (GeV/c) –e + e - channel –2 x 10 8 PbPb 10% most central eventsState S[10 3 ] B[10 3 ] S/B S/(S+B) 1/2 J/  ’’’’  (1S)  (2S)  (3S) –μ + μ - channel –1 month PbPb data taking...it is also worth noting that... suppression When suppression is taken into account, S/B decreases. Good sensitivity of J/Y,  (1S) &  (2S) to suppression scenarios.

23 rd March 2007, Moriond QCDChiara Zampolli 13 Jet Physics jets High energy partons from an initial hard scattering produce collimated “cascades” of particles, that is jets. jet quenching Traversing the medium, the energy of the partons is reduced because of energy loss, that is jet quenching occurs. Jet quenching changes the jet structure and fragmentation function (FF). parton fragmentation products QGP medium parton fragmentation products reveal information about the QGP medium

23 rd March 2007, Moriond QCDChiara Zampolli 14 Jet Physics in ALICE Thanks to the fact that multi-jet production happens up to E T ~ 20 GeV and to the high LHC jet rates at high E T, e-by-e jet reconstruction feasible  measurement of the initial parton 4-momentum and of the jet structure: decrease of particles with high z, increase of particles with low z broadening of the momentum distribution perpendicular to jet axis Background limited if: smaller cones are used in heavy-ion collisions: R = 0.3÷0.4 (80% of the energy) p T cuts to be applied Jet = excess of transverse energy over the background of the underlying event within a cone of radius R; R = 1 in pp collisions. z = p hadron /E T,jet Background ~ R 2 — no p T cut — p T >1 GeV/c — p T >2 GeV/c E T jet 100 GeV 150 GeV 50 GeV 30 GeV R E(R), charged [GeV]

23 rd March 2007, Moriond QCDChiara Zampolli 15 Reconstructed Jet: Observables N. Borghini, U. Wiedemann Increase on # of particles with low z Decrease on # of particles with high z Distortion due to medium-induced partonic energy loss Modifications of the transverse jet structure through for different cone size, jet shape as a function of the reconstructed energy, j T as a function of reconstructed energy. Jet Fragmentation Function Energy loss and radiated energy (gluon radiation) may be studied through the Jet Fragmentation Function dN/dξ, ξ = ln(1/z)  hump- backed plateau.

23 rd March 2007, Moriond QCDChiara Zampolli 16 ALICE First Day Physics Collider closure on 31 st August GeV November - December 2007: pp commissioning 900 GeV Detector initial configuation: Complete ITS, TPC, HMPID, Muon Arm, PMD, Trigger Dets, partial TOF, TRD, PHOS Already with ~ 10 4 events collected in the first run  First Physics feasibility: dN/dη distributions, p T spectra, multiplicity distributions, Baryon transport. ALICE magnet pict. by A. Saba

23 rd March 2007, Moriond QCDChiara Zampolli 17 ALICE First Day Physics reach µ arm 14 TeV Minimum Bias trigger provided by a coincidence between V0 counters (- 3.7 < η < -1.7 and 2.8 < η < 5.1). We expect a dN/dη excellent measurement in the central region thanks to the ITS + TPC detector V0 and FMD in the forward region. For 20 k events the limits are 5 GeV at 0.9 TeV and 10 GeV at 14 TeV. For 100 M events the limits are 15 GeV at 0.9 and 50 GeV at 14 TeV.

23 rd March 2007, Moriond QCDChiara Zampolli 18 Summary and Conclusions ALICE is a very versatile experiment, with a Heavy Ion physics programme spanning a wide variety of observables. ALICE is a very versatile experiment, with a Heavy Ion physics programme spanning a wide variety of observables. ALICE start-up is approaching, with the first pp commissioning collisions scheduled for November ALICE start-up is approaching, with the first pp commissioning collisions scheduled for November ALICE PbPb programme will then (end 2008) deal with an unexplored temperature and energy density regime, so that one should be ready to the unexpected and unknown. ALICE PbPb programme will then (end 2008) deal with an unexplored temperature and energy density regime, so that one should be ready to the unexpected and unknown.

23 rd March 2007, Moriond QCDChiara Zampolli 19 ALICE: What’s Up – Installation of the Beampipe March 2007 View from the inside of the space frame, the head of the beampipe is slowly progressing through the TPC. Half of the insertion has been carried out; In the background it is possible to see the ITS barrel.

Rencontres de Moriond QCD and Hadronic Interactions La Thuile, 23 rd March 2007 Chiara Zampolli `Take some more tea,’ the March Hare said to Alice, very earnestly. `I've had nothing yet,' Alice replied in an offended tone, `so I can't take more.’ `You mean you can't take LESS,' said the Hatter: `it's very easy to take MORE than nothing.’ L. Carroll, Alice in Wonderland

Rencontres de Moriond QCD and Hadronic Interactions La Thuile, 23 rd March 2007 Chiara Zampolli Back-Ups

23 rd March 2007, Moriond QCDChiara Zampolli 22 Six Layers of silicon detectors for precision tracking in |  |< D reconstruction (< 100  m) of the Primary Vertex Tracking+Standalone reconstruction of very low momentum tracks Particle identification via dE/dx for momenta < 1 GeV SPD - Silicon Pixel SDD - Silicon Drift SSD - Silicon Strip Secondary vertex Finding (Hyperons, D and B mesons) Three tecnhnologies: ALICE Inner Tracking System – ITS

23 rd March 2007, Moriond QCDChiara Zampolli 23 Efficient (>90%) tracking in  < 0.9  (p)/p < 2.5% up to 10 GeV/c Conventional TPC optimized for extreme track densities Two-track resolution < 10 MeV/c PID with dE/dx resolution < 10% Space-Point resolution 0.8 (1.2) mm in xy,(z), occupancy from 40% to 15% ALICE Time Projection Chamber – TPC

23 rd March 2007, Moriond QCDChiara Zampolli 24 ALICE Time Of Flight – TOF Large array at R ~ 3.7 m, covering |  | < 0.9 and full   Extensive R&D, from TB data: Intrinsic Resolution ~ 40 ps Efficiency > 99% Readout pads 3.5x2.5 cm cm TOF basic element: double-stack Multigap RPC strip Occupancy < 15% (O(10 5 ) readout channels) 2x5 gas gaps of 250mm

23 rd March 2007, Moriond QCDChiara Zampolli 25 ALICE PID 3  2  (dE/dx)

23 rd March 2007, Moriond QCDChiara Zampolli 26 Tracking Efficiency / Fraction of Fake Tracks for dN/dy = 2000, 4000, 6000, 8000 For dN/dy = 2000 ÷ 4000, efficiency > 90%, fake track probability < 5%!!! For dN/dy = 2000 ÷ 4000, efficiency > 90%, fake track probability < 5%!!! Full chain, ITS + TPC + TRD ALICE Tracking Performance

23 rd March 2007, Moriond QCDChiara Zampolli 27 ALICE p T Resolution

23 rd March 2007, Moriond QCDChiara Zampolli 28 ALICE PID efficiency contamination p dependence of: Central Pb + Pb HIJING events – kaon case ITS stand-alone TPC stand-alone TOF stand-alone Combining the PID information from different detectors allows a weaker momentum dependence of the efficiency (contamination) which stays higher (lower) or at least equal than with stand-alone detectors!!! ITS & TPC & TOF combined!!!