Heavy Ion Program in ALICE

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Heavy Ion Program in ALICE
A. Mastroserio Bari University INFN On behalf
of the ALICE collaboration

• Outline
• ALICE _at_ LHC
• Multiplicity, particle ratios
• high pt probes
• Summary and ALICE start up configuration

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ALICE _at_ LHC
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ALICE Setup
ALICE Setup
ITS
HMPID
TRD
TPC
MUON ARM
TOF
PHOS
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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 pTsuppression, open charm
  (Mass/color dependence of E loss)
• Fluctuation phenomena

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Multiplicity and hadronic yields
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HI Day 1 measurement
dNch/dy 2900
Eskola hep-ph/050649
dNch/dy 1200
ln(vs) extrapolation
ALICE performances tested up to dNch/d? 8000!
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ALICE performances
ALICE PPR Vol II J. Phys. G Nucl. Part. Phys. 32
(2006) 12952040 dNch/dy 6000
Efficiency ()
?pt/pt
?pt/pt
?pt/pt 3 at 100 GeV/c
Photon tagging also feasible direct ?, p0, ?
(PHOS)
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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
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 (?Sgt1 in the partition
function). Tch temperature depends on ?S and it
is lower than the chemical equilibrium
prediction. arXiv0707.4076v1 nucl-th.
3 lt ?S lt 5 ---gt 13 5
lt Tch (Mev) lt 125 EPJ C49 (2007)
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ALICE particle ID performances

• Unique capability to identify and reconstruct
  particles
• - stable particles through dE/dx (TPCITS)
  TOF Cherenkov (HMPID)
• p, k, p 0.15 5 GeV/c -gt 50 GeV/c
  (relativistic rise)
• Invariant mass reconstruction already done for
  many resonances and strange weak decaying hadrons
  (K0s, ?, ?, ?)

L
Pt limits for 107 central Pb-Pb events (1-year
data taking)
f (1020) ? KK-
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High PT probes
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High PT probes

• What if QGP is formed
• Partons propagate in a hot and dense medium
  before fragmenting in the vacuum
• E loss medium gt E lossvacuum and depends on the
  the length of the traversed medium
• High pT hadrons are suppressed
• Jet quenching -gt q medium dependent

QGP probes inclusive hadron yields at high pT,
Jet Structure
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Inclusive hadron yields
Factor 5 suppression _at_RHIC RAA 0.2
constant at pT gt 5 GeV/c

• Possible LHC scenario
• - light flavour RAA
• - constant 0.1 at 10lt pT (GeV/c) lt 20
  (gluon dominance)
• - slow rise up to 0.2 at 20 lt pT
  (GeV/c)lt 100
• arXiv0707.0564v1 hep-ph and
  arXiv0711.0974v1 hep-ph
• - slow rise to 0.4 up to pT lt 400 GeV/c
  
• arXiv0711.0974v1 hep-ph
• Heavy flavour / light flavour RAA
• - D quenching vs h quenching probes
  color charge
• dependence (?EQ lt ?E g)
• - B quenching vs D quenching probes
  parton mass
• dependence of parton E loss

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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

N. Borghini U. Wiedemann
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Jet Reconstruction RAA(x)
e-by-e jet reconstruction feasible
A. Morsch _at_ QM08
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Summary

• ALICE is a versatile experiment which will study
  the QGP formation in different physics domains
  (statisical thermodynamics, hydrodynamics,
  pQCD,etc.)
• Only few topics of the ALICE Heavy Ion Physics
  programme have been shown!

• first 105 events global event properties
• multiplicity, rapidity density
• elliptic flow
• first 106 events source characteristics
• particle spectra, resonances
• flow analysis
• interferometry
• first 107 events high-pt, heavy flavours
• jet quenching, heavy-flavour energy loss
• first 108 events heavy quark production
• J/?, ?

-gt initial conditions
-gt chemical equilibrium
-gt Parton E loss in the medium
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ALICE start up configuration

• complete fully installed commissioned
• ITS, TPC, TOF, HMPID, MUON SPECTROM., PMD, V0,
  T0, 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!
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Bkp slides
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QGP in lQCD
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HI collisions from SPS to LHC
Central collisions SPS RHIC LHC
?sNN (GeV) 17 200 5500
?Bj nom(GeV/fm3) 2.9 5 15 (?)
?QGP(fm/c) lt1 1.5-4 4-10 (?)
?0(fm/c) ?1 ?0.5 lt 0.2 (?)
?hard/?tot 50 98
Phase transition (lattice QCD) Tcr 170
MeV ecr 1 GeV/fm3

• New scenario
• Hard processes dominate AA cross section
• ?QGP at LHC gt RHIC parton dynamics dominate
  the fireball expansion

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Alice ID
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Hadron ratios
Non equilibrium
Chemical equilibrium
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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-gt s sbar (no hadron mass thresholds
to be overcome! )
arXiv0705.2511v1 nucl-ex 17 May 2007
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Jets
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LHC rates and HQ s