8-12 Feb. 2007Yves Schutz @ ICPAQGP51 Heavy-ion physics at LHC New states of matter ? (QGP, sQGP,...

8-12 Feb. 2007 Yves Schutz @ ICPAQGP5 1

Heavy-ion physics at LHC

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

New probes


SPS: ”New State of Matter created at CERN” (10 Feb. 2000)

7 dedicated experiments (NAxx, WAyy)

Compelling evidence for the existence of a new state of matter (3.2

GeV/fm3]>c, strangeness enhancement, J/ψ suppression, direct thermal photon radiation,…)

Interpretation in terms of QGP formation not unique

Pb+Pb √sNN = 17.3 GeV NA 49


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

Au+Au √sNN = 200 GeVSTAR


LHC: “The closest approximation of the Big Bang” (J. Ellis 02/2005)

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.

“It is dangerous to make predictions, especially about the future." G. Marx


What will be new at LHC

SPS RHIC LHC

√sNN (GeV) 17 200

dNch/dy 500 850

0QGP (fm/c) 1 0.2

T/Tc 1.1 1.9

(GeV/fm3) 3 5

QGP (fm/c) ≤2 2-4

f (fm/c) ~10 20-30

Vf(fm3) few 103 few 104

few 105 bigger

5500 X 28

1000-4000 ?

0.1 faster

3.0-4.2 hotter

15-60 denser

≥10longer

30-40

“The biggest step in energy in the history of heavy-ion collisions” G. Rolland


Formation of the real vacuum of QCD

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

mu= md = ms

mu = md

mu = md ; ms mu,d

HQ suppressed exp(-mc,b,t/T)

s(T)=4/(18log(5T/Tc))

RHIC

SPS

LHC

Not yet a StefanBoltzmann gas


A new kinematical regime

X<<1 Determines the properties of

the medium (QS=0.2A1/6√s= 2.7 GeV)

The QGP at LHC might evolve from a Color Glass Condensate in the initial state of the collision

J/ψ

ALICE PPR CERN/LHCC 2003-049²

10-6 10-4 10-2 100

x

108

106

104

102

100

Q2 (

GeV

2)

100 GeV

“LHC: The color glass machine”L. McLerran


A new kinematical regime

Q >> 1 Determines the probe of the

medium Q >> QCD, T (, r ~1/Q) ;

pt > 2 GeV/c

J/ψ

ALICE PPR CERN/LHCC 2003-049²

10-6 10-4 10-2 100

x

108

106

104

102

100

Q2 (

GeV

2)

100 GeV


Hard probes Particle production dominated

by hard processes Heavy quarks and weakly

interacting probes become accessible

Happen at t=0 → 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

RHICSPS

(h++h-)/2

0

17 GeV

200 GeV

5500 GeV=√s

LO p+p y=0

LHC:hard/total = 98% (50% at RHIC)


Dynamics of hadronisation : in vacuum

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

ET

hadronic final state

Lhadr ~ ET/Q2hadr


Dynamics of hadronisation: in medium

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

ET


Lhadr ~ ET/Q2hadr

E Ltherm ~ √(ET/q )^

^



Ltherm< Lhadr < Lmedium

The hard parton is thermalised in the heat bath Bulk properties of the medium from low ph

t ( ≤ 2 GeV/c) hadrons, leptons, photons

ET

E ~ ET

Experimental requirements: low pt threshold


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)

150



Ltherm~ Lhadr ~ Lmedium

The medium is a tool to modify the hadronisation process Dynamics of hadronisation (ph

t ~2-7 GeV/c)

ET


Lhadr ~ ET/Q2hadr



Medium modified fragmentation

Fragmentation, recombination ?

Experimental requirements: PID up to ~ 10 GeV/c

p/

Pt[GeV/c]



Ltherm> Lhadr > Lmedium The parton looses additional energy (qL2) The multiplicity, transverse momentum of the shower

broadens (qL) Leading hadron

ET



^

^

xET


Leading hadron (qL2)

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

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

Experimental requirements: high pt

^

q=5 GeV2/fm^

q=10 GeV2/fm^


Mass and color charge dependence

Egluon Equark,m0 Equark,m0

Experimental requirements: high pt electrons, vertexing

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

“Death of the dead cone”, I. Vitev


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

^


Jet heating

Sensitivity of jet energy distribution weak Broadening of kt

Modified longitudinal fragmentation function: (Z)-jet tagging

Salgado, Wiedemann, hep-ph/0310079

. kt


-jet tagging

Pb+Pb 40GeV → -jetR=0.3; pt> 2 GeV/c

Ejet/E xT=pT/E

RAA

Experimental requirements: jet calorimetry, low xt hadrons, high pt , e


1+2 experiments at the LHCATLASCMSALICE


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


Heavy ion experiment at LHC

ALICE will meet the challenge to measure flavor content and phase-space distribution event-by-event: Most (2 * 1.8 units ) 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;


ALICE: the dedicated HI experiment

Solenoid magnet 0.5 T

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

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

Specialized detectors:• HMPID• PHOS

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

Cosmic rays trigger


Proposed ALICE EMCAL

EM Sampling Calorimeter (STAR Design)

Pb-scintillator linear response -0.7 < < 0.7 /3 < <

Energy resolution ~15%/√E


Alice uses ~all known techniques!

0 1 2 3 4 5 p (GeV/c)

1 10 100 p (GeV/c)

TRD e / PHOS /0

TPC + ITS (dE/dx)

/K

/K

/K

K/p

K/p

K/p

e /

e /

HMPID (RICH)

TOF

Aerogel Cherenkov 10 GeV/c

ALICE PID

EMCAL


Jet Phase Space

0 1 2 10 100

pt (GeV/c)

Bulk properties

Hard processesModified by the medium

T=QCD Qs

ALICE Tracking & PID

Jets from Correlations and Leading Particles

Reconstructed Jets

Mini-jets 100/event 1/event 100K/year

CMS&ATLAScalorimetry

“Jet physics will dominate the LHC heavy-ion program”, ALICE will be the main contender of the “race for jet quenching” I. Vitev


LHC


ATLAS


CMS


ALICE


More at ICPAQGP6

The first 15 minutes; Lint=1b-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

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

8-12 Feb. 2007Yves Schutz @ ICPAQGP51 Heavy-ion physics at LHC New states of matter ? (QGP, sQGP,...

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