ALICE at LHC

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ALICE at LHC

• New states of matter ? (QGP, wQGP, sQGP, bsQGP,
  CGC,)
• New probes

LHC not relevant for the search of the critical
point Marek Gazdzicki
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SPS New State of Matter created at CERN (10
Feb. 2000)
PbPb vsNN 17.3 GeV NA 49

• 7 dedicated experiments (NAxx, WAyy)
• Compelling evidence for the existence of a new
  state of matter (e 3.2 GeV/fm3gtec, strangeness
  enhancement, J/? suppression, direct thermal
  photon radiation,)
• Interpretation in terms of QGP formation not
  unique

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RHIC The discovery of the QGP at RHIC (M.
Gyulassy QM 2004)

• 4 multipurpose experiments (BRAHMS, PHENIX,
  PHOBOS, STAR)
• Empirical lines of evidence
• Energy density (5 GeV/fm3) well beyond critical
  value
• Large elliptic flow early collective behavior at
  partonic level
• Jet quenching, mono jets absorption of partons
  in a color dense opaque medium
• dA control experiment
• Interpreted in terms of a strongly coupled QGP
  and a new QCD state (?) Color Glass Condensate

AuAu vsNN 200 GeV STAR
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LHC The closest approximation of the Big Bang
It is dangerous to make predictions, especially
about the future."

• One heavy ion experiment, ALICE
• In 04/2007, LHC will deliver first pp at 14 TeV
  collisions,
• and soon after PbPb collisions at vsNN 5.5 TeV.

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What will be new at LHC








few 105 bigger






10 longer
30-40 longer





15-60 denser




3.0-4.2 hotter



0.1 faster


1000-4000 ?

5500 X 28
SPS RHIC LHC
vsNN (GeV) 17 200
dNch/dy 500 850
t0QGP (fm/c) 1 0.2
T/Tc 1.1 1.9
e (GeV/fm3) 3 5
tQGP (fm/c) 2 2-4
tf (fm/c) 10 20-30
Vf(fm3) few 103 few 104
The biggest step in energy in the history of
heavy-ion collisions
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Formation of the real vacuum of QCD

• Weakly interacting gas of mass less quarks (3
  flavors) and gluons with restored Chiral
  symmetry

Not yet a StefanBoltzmann gas
RHIC
as(T)4p/(18log(5T/Tc))
LHC
SPS
mu md ms mu md mu md ms ? mu,d HQ
suppressed exp(-mc,b,t/T)
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A new kinematical regime
108 106 104 102 100

• xltlt1
• Determines the properties of the medium
  (QS0.2A1/6vsd 2.7 GeV)
• The QGP at LHC might evolve from a Color Glass
  Condensate in the initial state of the collision

Q2 (GeV2)
LHC The color glass machine L. McLerran 
ALICE PPR CERN/LHCC 2003-049²
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A new kinematical regime

• Q gtgt 1
• Determines the probe of the medium
• Q gtgt LQCD, T (Dt, Dr 1/Q) pt gt 2 GeV/c

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Hard probes

• Particle production dominated by hard processes
• Heavy quarks and weakly interacting probes become
  accessible
• Happen at t0 ? initial stage of the collision
• Have a large virtuality ? short formation time
• Probe matter at very early times ? QGP
• Can be calculated by pQCD ? predictions

LHC shard/stotal 98 (50 at RHIC)
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Dynamics of hadronisation in vacuum
hadronic final state
ET
Lhadr ET/Q2hadr

• The medium modifies the vacuum dynamics
• Modifications are imprinted in the hadronic final
  state

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Dynamics of hadronisation in medium
hadronic final state
ET
Lhadr ET/Q2hadr

• The radiated energy (DE) depends on the
  properties of the
• medium (the transport coefficient q)
• The competition between thermalisation (DEE) and
  
• hadronisation depends on the hard parton
  transverse energy.

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Dynamics of hadronisation in medium
ET

• Lthermlt Lhadr lt Lmedium
• The hard parton is thermalised in the heat bath
• Bulk properties of the medium from low pht ( 2
  GeV/c) hadrons, leptons, photons

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Bulk properties of the LHC medium

• Monotonic extrapolation from RHIC but changes in
• Expansion dynamics and (elliptic flow, transverse
  volume, event by event fluctuations, )
• Freeze out (temperature, charm, )
• Thermal photons (real virtual)

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Dynamics of hadronisation in medium
hadronic final state
ET
Lhadr ET/Q2hadr

• Ltherm Lhadr Lmedium
• The medium is a tool to modify the hadronisation
  process
• Dynamics of hadronisation (pht 2-7 GeV/c)

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Medium modified fragmentation
p/p
PtGeV/c

• Fragmentation, recombination ?

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Dynamics of hadronisation in medium
xET
hadronic final state
ET

• Lthermgt Lhadr gt Lmedium
• The parton looses additional energy (qL2)
• The multiplicity, transverse momentum of the
  shower broadens (qL)
• Leading hadron

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Leading hadron (qL2)

Eskola, Honkanen, Salgado, Wiedemann
Nucl Phys A, hep-ph/0406319

• Probe the reduced energy of the parton with the
  reduced energy of the leading hadron.
• But surface emission limits the sensitivity to
  the medium properties

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Mass and color charge dependence
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Jet heating (qL)

• At LHC jets can be reconstructed in the HI
  environment
• The measurement of the jet structure provides a
  better sensitivity to the medium properties

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Jet heating
. kt

• Sensitivity of jet energy distribution weak
• Broadening of kt
• Modified longitudinal fragmentation function
  g(Z)-jet tagging

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g-jet tagging
PbPb 40GeV ? g-jet R0.3 ptgt 2 GeV/c
Ejet/Eg
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12 experiments at the LHC
ALICE
ATLAS
CMS
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ALICE Physics Program

• Deconfinement
• charmonium and bottomonium spectroscopy
• Energy loss of partons in quark gluon plasma
• jet quenching high pt spectra
• open charm and open beauty
• Chiral symmetry restoration
• neutral to charged ratios
• resonance decays
• Fluctuation phenomena - critical behavior
• event-by-event (vN) particle composition and
  spectra
• pp collisions in a new energy domain

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Heavy ion experiment at LHC

• ALICE will meet the challenge to measure flavor
  content and phase-space distribution
  event-by-event
• Most (2p 1.8 units h) of the hadrons (dE/dx
  ToF), leptons (dE/dx, transition radiation,
  magnetic analysis) and photons (high resolution
  EM calorimetry)
• Track and identify from very low (lt 100 MeV/c
  soft processes) up to very high pt (gt100 GeV/c
  hard processes)
• Identify short lived particles (hyperons, D/B
  meson) through secondary vertex detection
• Identify jets

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ALICE PID
Alice uses all known techniques!
p/K
TPC ITS (dE/dx)
K/p
e /p
p/K
e /p
TOF
K/p
p/K
HMPID (RICH)
K/p
0 1 2
3 4
5 p (GeV/c)
TRD e /p
PHOS g /p0
EMCAL
1 10
100 p (GeV/c)
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Jet Phase Space
Jet physics will dominate the LHC heavy-ion
program, ALICE will be the main contender of the
race for jet quenching
Qs
TLQCD
Mini-jets 100/event
100K/year
1/event
Bulk properties
Hard processes Modified by the medium
ALICE Tracking PID
Jets from Correlations and Leading Particles
Reconstructed Jets
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ALICE
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The ALICE program in 2007 on wards
sPbPb 8barn LPbPb 1027cm-2s-1 t004/2007

• The first 15 minutes Lint1mb-1
• Event multiplicity, low pt hadronic spectra,
  particle ratios
• The first month Lint0.1-1nb-1
• Rare high pt processes jets, D,B, quarkonia,
  photons, electrons
• The following years
• pA, A scan, E scan

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ALICE the dedicated HI experiment
Cosmic rays trigger

• Forward detectors
• PMD
• FMD, T0, V0, ZDC

• Specialized detectors
• HMPID
• PHOS

• Central tracking system
• ITS
• TPC
• TRD
• TOF

• MUON Spectrometer
• absorbers
• tracking stations
• trigger chambers
• dipole

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Proposed ALICE EMCAL

• EM Sampling Calorimeter (STAR Design)
• Pb-scintillator linear response
• -0.7 lt h lt 0.7
• p/3 lt F lt p
• Energy resolution 15/vE