Heavy Ion Program in ALICE A Mastroserio Bari

Heavy Ion Program in ALICE A. Mastroserio Bari University & INFN On behalf of the ALICE collaboration Outline - ALICE @ LHC - Multiplicity, particle ratios - high pt probes - Summary and ALICE start up configuration 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 1

ALICE @ LHC ~8. 5 km ALICE SPS CERN 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 2

ALICE Setup ITS ALICE Setup HMPID TRD TPC MUON ARM TOF PHOS 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 3

Physics topics of ALICE • Event characterization Multiplicity, centrality • Bulk properties of the hot and dense medium (dynamics of hadronization) hadron ratios, hadronic resonances • Chiral symmetry restoration Short lived resonance masses • Space-time fireball description and fireball expansion dynamics Momentum correlations (HBT), Radial and anisotropic flow • Heavy quark production Charmonium and bottonium (Debye screening, recombination(? )) • Partonic energy loss in QGP Jet reconstruction, Jet quenching, high pt spectra, inclusive high p. Tsuppression, open charm (Mass/color dependence of E loss) • Fluctuation phenomena Event-by-Event analysis ………. . • 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 4

Multiplicity and hadronic yields 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 5

HI Day 1 measurement d. Nch/dy = 2900 Eskola hep-ph/050649 d. Nch/dy = 1200 ln(√s) extrapolation ε(RHIC) ~ 15 Ge. V/fm 3 d. Nch/dy ~ 1200 -2900 ε(LHC) ~ 3 - 5 x RHIC ALICE performances tested up to d. Nch/dη = 8000! 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 6

Efficiency (%) ALICE performances ALICE PPR Vol II J. Phys. G: Nucl. Part. Phys. 32 (2006) 1295– 2040 d. Nch/dy = 6000 pt/pt ~ 3 % at 100 Ge. V/c Photon tagging also feasible: direct , π0, η (PHOS) 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 7

Hadronic ratios Statistical models assume a chemical freeze out stage: hadron abundances are fixed. Chemical equilibrium model: depends on two parameters (T, μB) and it is able to describe succesfully hadron yields from SPS to RHIC energies. It predicts a chemical freeze out at LHC energies: A. Andronic, P. Braun-Munzinger, J. Stachel: ar. Xiv: 0707. 4076 v 1 [nucl-th] rate of strange (especially multi-strange) hadrons is expected to strongly increase with respect to the equilibrium yields A. Andronic, P. Braun-Munzinger, J. Stachel. Nucl. Phys. A 772: 167 -199, 2006 Non-equilibrium scenario: the strangeness phase space is oversaturated ( S>1 in the partition function). Tch temperature depends on S and it is lower than the chemical equilibrium prediction. ar. Xiv: 0707. 4076 v 1 [nucl-th]. 3 < S < 5 ---> 13 5 < Tch (Mev) < 125 EPJ C 49 (2007) 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 8

ALICE particle ID performances Unique capability to identify and reconstruct particles - “stable particles” through d. E/dx (TPC+ITS) + TOF + Cherenkov (HMPID) π, k, p : 0. 15 – 5 Ge. V/c -> 50 Ge. V/c (relativistic rise) - Invariant mass reconstruction already done for many resonances and strange weak decaying hadrons (K 0 s, , , ) L Pt limits for 107 central Pb-Pb events (1 -year data taking) resolution ~ 1. 2 Me. V f (1020) K+K- 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 9

High PT probes 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 10

High PT probes What if QGP is formed: - Partons propagate in a hot and dense medium before fragmenting in the vacuum - E loss medium > E lossvacuum and depends on the length of the traversed medium - High p. T hadrons are suppressed - “Jet quenching” -> q [medium dependent] QGP probes: inclusive hadron yields at high p. T, Jet Structure 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 11

Inclusive hadron yields Factor 5 suppression @RHIC: RAA ~ 0. 2 constant at p. T > 5 Ge. V/c Possible LHC scenario: - light flavour RAA - constant ~0. 1 at 10< p. T (Ge. V/c) < 20 (gluon dominance) - slow rise up to 0. 2 at 20 < p. T (Ge. V/c)< 100 [ar. Xiv: 0707. 0564 v 1 [hep-ph] and ar. Xiv: 0711. 0974 v 1 [hep-ph] - slow rise to 0. 4 up to p. T < 400 Ge. V/c [ar. Xiv: 0711. 0974 v 1 [hep-ph] ] - Heavy flavour / light flavour RAA : - D quenching vs h quenching probes color charge dependence (ΔEQ < ΔE g) - B quenching vs D quenching probes parton mass 9/17/2020 dependence of parton E loss A. Mastroserio - XLIIIth Rencontres de Moriond 12

Jet physics in HI Jet in QCD: cascades of consecutive emissions of partons initiated by partons from an initial hard scattering What if QGP is formed: -The initial energy of fast partons is degraded in the medium - Broadening of the parton shower along the fast parton direction - Modified jet structure and fragmentation functions 9/17/2020 N. Borghini & U. Wiedemann A. Mastroserio - XLIIIth Rencontres de Moriond 13

Jet Reconstruction: RAA(x) e-by-e jet reconstruction feasible A. Morsch @ QM 08 Ge. V 2/fm [AQM] 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 14

Summary § ALICE is a versatile experiment which will study the QGP formation in different physics domains (statisical thermodynamics, hydrodynamics, p. QCD, etc. ) § Only few topics of the ALICE Heavy Ion Physics programme have been shown! q first 105 events: global event properties q multiplicity, rapidity density q elliptic flow q first 106 events: source characteristics q particle spectra, resonances q flow analysis q interferometry q first 107 events: high-pt, heavy flavours q jet quenching, heavy-flavour energy loss q first 108 events: heavy quark production q J/Ψ, 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond -> initial conditions -> chemical equilibrium -> Parton E loss in the medium 15

ALICE start up configuration • complete – fully installed & commissioned – ITS, TPC, TOF, HMPID, MUON SPECTROM. , PMD, V 0, T 0, FMD, ZDC, ACORDE • partially completed – TRD (25%) to be completed by 2009 – PHOS (60%) to be completed by 2010 – HLT (30%) to be completed by 2009 – EMCAL (0%) to be completed by 2010/11 • at start-up full hadron and muon capabilities • partial electron and photon capabilities …. looking forward to “detect” this! 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 16

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Bkp slides 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 18

QGP in l. QCD 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 19

HI collisions from SPS to LHC Phase transition Central collisions SPS RHIC LHC (lattice QCD): s. NN (Ge. V) 17 200 5500 Tcr ~ 170 Me. V Bj nom(Ge. V/fm 3) 2. 9 5 15 (? ) QGP(fm/c) <1 1. 5 -4 4 -10 (? ) 0(fm/c) 1 0. 5 < 0. 2 (? ) ~ 50% ~ 98% εcr~ 1 Ge. V/fm 3 hard/ tot New scenario: - Hard processes dominate AA cross section - QGP at LHC > RHIC : parton dynamics dominate the fireball expansion 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 20

Alice ID 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 21

Hadron ratios Non equilibrium Chemical equilibrium 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 22

Strangeness production in HI - No initial net strangeness - strange particle are a direct consequence of the collision dynamics Strangeness production mechanism is in the QGP phase: gg-> s sbar (no hadron mass thresholds to be overcome! ) ar. Xiv: 0705. 2511 v 1 [nucl-ex] 17 May 2007 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 23

>107 E(R), charged [Ge. V] 1 year data taking Jets Background ~ R 2 — no p. T cut — p. T >1 Ge. V/c ETjet — p. T >2 Ge. V/c 150 Ge. V 100 Ge. V 50 Ge. V 30 Ge. V R 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 24

LHC rates and HQ σ 9/17/2020 A. Mastroserio - XLIIIth Rencontres de Moriond 25