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					  Heavy-ion physics at LHC


                 New states of matter ? (QGP,
                 sQGP, bsQGP, CGC,…)

                 New probes


8-12 Feb. 2007            Yves Schutz @ ICPAQGP5   1
      SPS: ”New State of Matter created at
      CERN” (10 Feb. 2000)
Pb+Pb √sNN = 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/fm3]>ec, strangeness
                                           enhancement, J/ψ
                                           suppression, direct thermal
                                           photon radiation,…)
                                          Interpretation in terms of
                                           QGP formation not unique



      8-12 Feb. 2007    Yves Schutz @ ICPAQGP5                           2
RHIC: “The discovery of the QGP at
RHIC” (M. Gyulassy QM 2004)
Au+Au √sNN = 200 GeV
                                   4 multipurpose experiments
                                    (BRAHMS, PHENIX, PHOBOS, STAR)
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
8-12 Feb. 2007         Yves Schutz @ ICPAQGP5                        3
   LHC: “The closest approximation of
   the Big Bang” (J. Ellis 02/2005)
“It is dangerous to make predictions, especially about the future." G. Marx




                                                One heavy ion experiment,
                                                 ALICE, + CMS & ATLAS;

                                                In 04/2007, LHC will deliver
                                                 first pp at 14 TeV collisions,

                                                and soon after PbPb
                                                 collisions at √sNN= 5.5 TeV.



   8-12 Feb. 2007               Yves Schutz @ ICPAQGP5                            4
         What will be new at LHC
                          SPS      RHIC                  LHC
     √sNN (GeV)            17       200                  5500      X 28
       dNch/dy            500       850              1000-4000       ?
     t0QGP (fm/c)          1         0.2                0.1        faster
         T/Tc              1.1       1.9                 3.0-4.2    hotter
     e (GeV/fm3)           3          5                  15-60     denser
     tQGP (fm/c)           ≤2       2-4                    ≥10
                                                                   longer
       tf (fm/c)          ~10      20-30                 30-40
       Vf(fm3)           few 103   few 104              few 105    bigger


“The biggest step in energy in the history of heavy-ion collisions” G. Rolland
        8-12 Feb. 2007              Yves Schutz @ ICPAQGP5                   5
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 = m d
                                                    mu = md ; ms  mu,d
                                                    HQ suppressed exp(-mc,b,t/T)



8-12 Feb. 2007            Yves Schutz @ ICPAQGP5                             6
       A new kinematical regime
                                               108


   X<<1                                       106
      Determines the properties of
       the medium (QS=0.2A1/6√sd=



                                   Q2 (GeV2)
       2.7 GeV)
      The QGP at LHC might                     100
                                               104 GeV
       evolve from a Color Glass
       Condensate in the initial
       state of the collision
                                               102
                                      J/ψ

    “LHC: The color glass machine”             100
    L. McLerran                                             10-6        10-4         10-2       100
                                                 ALICE PPR CERN/LHCC 2003-049²   x
       8-12 Feb. 2007            Yves Schutz @ ICPAQGP5                                     7
        A new kinematical regime
                                                   108


                                                   106
   Q >> 1



                                       Q2 (GeV2)
       Determines the probe of the
        medium
       Q >> LQCD, T (Dt, Dr ~1/Q) ;
                                                    100
                                                   104 GeV
        pt > 2 GeV/c

                                                   102
                                         J/ψ

                                                   100
                                                                10-6        10-4         10-2       100
                                                     ALICE PPR CERN/LHCC 2003-049²   x
        8-12 Feb. 2007            Yves Schutz @ ICPAQGP5                                        8
      Hard probes
LHC: shard/stotal = 98%                 (50% at RHIC)      Particle production dominated
                                                            by hard processes
                                                           Heavy quarks and weakly
                               LO p+p y=0                   interacting probes become
                       (h++h-)/2   √s   =   5500 GeV        accessible
                          p0                 200 GeV
                                                           Happen at t=0 → initial stage
                                              17 GeV        of the collision
                                                                  Have a large virtuality →
                           LHC                                     short formation time
                  RHIC                                             Probe matter at very early
         SPS                                                       times → QGP
                                                                  Can be calculated by pQCD
      8-12 Feb. 2007
                                                                   → predictions
                                              Yves Schutz @ ICPAQGP5                        9
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

8-12 Feb. 2007                   Yves Schutz @ ICPAQGP5                          10
Dynamics of hadronisation: in
medium
                        DE                     ^
                                 Ltherm ~ √(ET/q )


                                                          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 (DE=E) and
        hadronisation depends on the hard parton transverse energy.

8-12 Feb. 2007                   Yves Schutz @ ICPAQGP5                          11
Dynamics of hadronisation: in
medium
                           DE ~ ET




      ET


       Ltherm< Lhadr < Lmedium
                The hard parton is thermalised in the heat bath
                Bulk properties of the medium from low pht ( ≤ 2 GeV/c)
                 hadrons, leptons, photons
                           Experimental requirements: low pt threshold

8-12 Feb. 2007                       Yves Schutz @ ICPAQGP5                12
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)




8-12 Feb. 2007                     Yves Schutz @ ICPAQGP5
                                                            150          13
Dynamics of hadronisation: in
medium
                          DE                     ^
                                   Ltherm ~ √(ET/q )


                                                            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)

8-12 Feb. 2007                     Yves Schutz @ ICPAQGP5                          14
Medium modified
fragmentation
       p/p




                                                         Pt[GeV/c]
    Fragmentation, recombination ?
                 Experimental requirements: PID up to ~ 10 GeV/c
8-12 Feb. 2007                  Yves Schutz @ ICPAQGP5               15
Dynamics of hadronisation: in
medium
                          DE                    ^
                                  Ltherm ~ √(ET/q )
                                                                   xET
                                                           hadronic final state
      ET




       Ltherm> Lhadr > Lmedium
                                                     ^
                 The parton looses additional energy (qL2)
                The multiplicity, transverse momentum of the shower
                            ^
                 broadens (qL)
                Leading hadron
8-12 Feb. 2007                    Yves Schutz @ ICPAQGP5                          16
                ^
Leading hadron (qL2)
                                   Eskola, Honkanen, Salgado, Wiedemann
                                             Nucl Phys A, hep-ph/0406319




                                                          ^
                                                          q=5 GeV2/fm
                                                            ^
                                                            q=10 GeV2/fm



       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

                     Experimental requirements: high pt
8-12 Feb. 2007                  Yves Schutz @ ICPAQGP5                     17
Mass and color charge
dependence
                 DE gluon  DE quark, m 0  DE quark, m0

                                                           Armesto, Dainese,
                                                           Salgado, Wiedemann
                                                           hep-ph/0501225



                                                           “Death of the dead
                                                           cone”, I. Vitev




                  Experimental requirements: high pt electrons, vertexing
8-12 Feb. 2007                    Yves Schutz @ ICPAQGP5                        18
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




8-12 Feb. 2007               Yves Schutz @ ICPAQGP5             19
    Jet heating
                     Salgado,
                     Wiedemann,
                     hep-ph/0310079




                            . kt




      Sensitivity of jet energy distribution weak
      Broadening of kt
      Modified longitudinal fragmentation function: g(Z)-jet tagging
    8-12 Feb. 2007                    Yves Schutz @ ICPAQGP5            20
g-jet tagging
   Pb+Pb 40GeV → g-jet                   RAA
   R=0.3; pt> 2 GeV/c




                          Ejet/Eg                                    xT=pT/Eg
      Experimental requirements: jet calorimetry, low xt hadrons, high pt g, e
8-12 Feb. 2007                  Yves Schutz @ ICPAQGP5                      21
                                          ALICE
                                          ATLAS
                                           CMS
1+2 experiments at the LHC




8-12 Feb. 2007   Yves Schutz @ ICPAQGP5     22
    ALICE Physics Program

   Deconfinement:
        charmonium and bottomium 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 (√N) particle composition and spectra
   pp collisions in a new energy domain

    8-12 Feb. 2007         Yves Schutz @ ICPAQGP5               23
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 (< 100 MeV/c; soft
                 processes) up to very high pt (>100 GeV/c; hard
                 processes);
                Identify short lived particles (hyperons, D/B meson)
                 through secondary vertex detection;
                Identify jets;
8-12 Feb. 2007                          Yves Schutz @ ICPAQGP5                        24
    Solenoid magnet 0.5 T            Cosmic rays trigger

     ALICE: the
Forward detectors: dedicated HI experiment
  • PMD
  • FMD, T0, V0, ZDC
          Specialized detectors:
            • HMPID
            • PHOS


 Central tracking system:
                                      MUON Spectrometer:
   • ITS
                                        • absorbers
   •TPC
                                        • tracking stations
   • TRD
                                        • trigger chambers
   • TOF
                                        • dipole
    8-12 Feb. 2007   Yves Schutz @ ICPAQGP5            25
     Proposed ALICE EMCAL

   EM Sampling Calorimeter
    (STAR Design)

   Pb-scintillator linear
    response
          -0.7 < h < 0.7
          p/3 < F < p

   Energy resolution ~15%/√E



     8-12 Feb. 2007           Yves Schutz @ ICPAQGP5   26
         ALICE PID
                                                                          Alice uses ~all
                                                                          known techniques!
TPC + ITS                                                                                        p/K
                                                                                                K/p
(dE/dx)                                                                                         e /p

                                                 p/K
TOF           e /p
                                                                             K/p

HMPID                                                               p/K
(RICH)                                                                                   K/p

                0                 1         2                 3               4        5 p (GeV/c)
                             Aerogel Cherenkov
                                                                                         10 GeV/c
 TRD     e /p
 PHOS EMCAL               g /p0

                                       1                             10             100 p (GeV/c)

         8-12 Feb. 2007                    Yves Schutz @ ICPAQGP5                          27
                                                “Jet physics will dominate the
                                                LHC heavy-ion program”, ALICE
      Jet Phase Space                           will be the main contender of
                                                the “race for jet quenching” I.
                                                Vitev
0             1        2          10                            100
    T=LQCD             Qs                                         pt (GeV/c)
    Mini-jets 100/event           1/event                         100K/year

           Bulk                        Hard processes
        properties                  Modified by the medium
                       ALICE Tracking & PID
                                                           CMS&ATLAS
                                                           calorimetry

                       Jets from Correlations and Leading Particles
                                                   Reconstructed Jets
      8-12 Feb. 2007              Yves Schutz @ ICPAQGP5                      28
                                          LHC




8-12 Feb. 2007   Yves Schutz @ ICPAQGP5    29
                                          LHC




8-12 Feb. 2007   Yves Schutz @ ICPAQGP5     30
                                          ATLAS




8-12 Feb. 2007   Yves Schutz @ ICPAQGP5      31
                                          CMS




8-12 Feb. 2007   Yves Schutz @ ICPAQGP5    32
                                          ALICE




8-12 Feb. 2007   Yves Schutz @ ICPAQGP5      33
More at ICPAQGP6

     sPbPb = 8barn; LPbPb 1027cm-2s-1; t0=04/2007

      The first 15 minutes; Lint=1mb-1
                Event multiplicity, low pt hadronic spectra,
                 particle ratios
      The first month; Lint=0.1-1nb-1
                Rare high pt processes: jets, D,B, quarkonia,
                 photons, electrons
      The following years:
                pA, A scan, E scan
8-12 Feb. 2007                   Yves Schutz @ ICPAQGP5          34

				
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