The h eavy i on c ollider e xperiment @ LHC A L I C E

Ginés MARTINEZ, SUBATECH Rencontres de Moriond March 17-24 2001 1

The heavy ion collider experiment @ LHC

A L I C EGinés MARTINEZ#

for the ALICE Collaboration

#Photon Group @ SUBATECH(IN2P3/CNRS – ENM - UN) Nantes, France


Outlook

1. Why a Heavy Ion Experiment @ LHC?

2. Goals3. Building ALICE


The study of the Quark Gluon Plasma

• QCD-thermodynamics• Properties of the QGP and of

the phase transition:– Chiral transition– Deconfinement

Lattice QCD calculationsnf=2 Tc = 173±8±SysErr MeVnf=3 Tc = 153±8±SysErr MeVc= 700 ± 300 MeV

Krasch QM2001


Towards QCD thermodynamics

The TOOLS:Heavy Ion Collisions: SPS => RHIC => LHC

The relation with QCD at finite temperature – The pp & pA baseline– Equilibration– Probes of QGP formation?– QGP Initial conditions?

Collision dynamics


collision dynamicsp+p and p+A

baseline !Sensitivity to late stages

in HI collisions!

The QGP phase

Final state probes

Penetratingprobes


Why HI program @ LHC ?

Central collisions SPS RHIC LHC

s1/2(GeV) 17 200 5500

dNch/dy 500 700-1500 3-8 x103

(GeV/fm3) 2.5 3.5-7.5 15-40

Vf(fm3) 103 7x103 2x104

QGP (fm/c) <1 1.5-4.0 4-10

0 (fm/c) ~1 ~0.5 <0.2

J. Schukraft QM2001@ LHC : Hotter – bigger - longer


The gluon-gluon physics…

• Gluon distribution in nuclei grows for small values of x = 2pT /s1/2 and high gluon densities are reached .

• For high densities (T >> QCD ) in large nuclei & small

x, the gluon distribution can be computed in the weak coupling method.• The classical color field.

• A large number of gluons are freed in the early stage of the collision => Equilibration

PRD10(74)1649, PRC49(94)2233, PRD49(94)3352, PRD53(96)458, PRC56(97)2219


• Better connection with QCD theory (via the asymptotically free field theory) A E– Initial gluon multiplicity (R.Venugopalan QM01, PRL86(01)1717)

– Initial equilibration conditions (D. Son QM01,hep-ph/0009237)

– Longer lifetime of the plasma

– Ideal plasma c ~ 5 : higher T

– Zero baryon density (already p/p ~ 0.6 @ RHIC) – New probes : Jets, Open charm & beauty, bottonium

Advantages of Pb+Pb collisions @ LHC


Final state probes

• Forward energy• dN/dy • hadron pT distribution • Particle ratios • Strange particles

• Multiplicity

• Energy Density

• HBT and dynamical evolution

• Freeze-out temperature

• Fluctuations

• Collective motion

• 12200 ’s• 1700 K’s• 700 ’s• 570 p, n, p, n ‘s• ….

-1<<1

Pb+Pb @ 5.5A TeV


Penetrating probes

• Real and virtual photons

• Quarkonia: J/ & Y • Open Charm &

Beauty• Light vector mesons• Jets

• Initial stage

• Thermal radiation: Tini

• Colour screening of heavy quarks

• Jet-matter interaction• Chiral transition


Jet Matter interaction

B A

1-3 GeV/fm#

#Interference with vacuum and LPM,

Jet enhancementEjet dependence of E

pT> 10 – 20 GeV

1. High pT particle distributions2. Identification of jets …3. Tagging with photons:

• High pT particles• Jets

Looking for Jet matter interaction:

Urs. Wiedemann QM2001 et NPB588(00)203

Large production of jets @ LHC energies1 jet/GeV/s in the ALICE acceptance

at ET =50 GeV


Building ALICE

• Event Characterisation

• dNch/dy

• pT distribution• Particle ratios• Strange baryons• Fluctuations

• Light vector mesons• Quarkonium• Open charm & beauty• Photon & Dilepton• Jet quenching• …


dNch/d =1~ 8000

• Time Projection Chamber: Main tracking detector of ALICE central barrel• Inner radius: Track separationRin = 0.8 m• Outer radius: dE/dx & p resolution# Rout= 2.5 m • Large acceptance <0.9• 200Hz rate capability• MWPC read-out 32 m2, 40% Oc• 5 105 pads x 500 time bins• 60 Mbyte/evt => DC, RoI, L3 …

#Magnetic field of the L3 magnet 0.4T 5% @ 5 GeV/c

1. PID below ~600 MeV/c 2. Low p tracks

Tracking efficiency ~90%2 tracks eff. 80% p>15 MeV/c

TPC

5 m

Ne+CO2(10%)


The ALICE PID

pT distributions•Particles ratios: Tfreeze-out

•Fluctuations•Strangeness production•Light vector mesons•Open charm •Jet physics

• 0.5 < p < 5 GeV/c

• e, , K, p

Time of FlightHigh Momentum Particle IdentificationTransition Radiation Detector

ToF prototypeALICE solution

• Large acceptance• MRPC• = 150 ps• ,K,p• 0.5<p<2.5 GeV/c

ToF

10cm

Multigap Resistive

Plate Chamber


High momentum particles

HMPID

High Momentum PID:• Hard processes

1 GeV/c < p < 5 GeV/cRich-imaging techniqueSmall acceptance

7x


Electron Identificator of ALICE

• Electron detector• 10-3 pion rejection• Large acceptance• Transition Radiation Detector

6x

• J/ in Zero baryon density• Open charm normalization• J/ source from Open Beauty• D annihilation?• production• Light vector resonances:

e channel

~ 103

EX ~ 3-30 KeV

Pb+Pb central collisionsTRD


Primary and secondary Vertex Position

• Secondary vertex from hyperon decays• Open charm & beauty physics• Tracking of low pT particles• Improving momentum resolution• Strangelets

• Large acceptance• 15000 tracks • ~100m in r

6 Silicon layers:1. 2 Silicon Pixel layers2. 2 Silicon Drift layers3. 2 Silicon Strip layers

ITS

K-

pITS

D =>Kevt


Photon detection• Thermal radiation• High pt physics• Tagged jets

• 1200 pT>40 GeV/c

• EM calorimeter• PbWO4: spectrometer: 0• Small acceptance 0.07 • 1< pT < 5 GeV/c• 5< pT <100 GeV/c

5x

PHOS ModulePHOS

Th

erm

al/D

ecay

1

0.1

10

1

2 3 pT(GeV/c)4

5%

hep-ph/9906325


Di muon channel

DiMuon

Quarkonium physics:J/ and Y families~ 100 MeV2.4 < < 4.0

ecoin.:•Intermediate rapidity•DD, BB production


ALICE = The result of QGP physics requirements at LHC

+PMDFMDCASTORZDCTriggerDAQOffline


Running conditions

• Pb+Pb @ 5.5A TeV

• 106s per year

• 8000 Hz (L=1027 cm-2s-1)

• Data rate full ALICE 50 Hz (TPC challenge)

• pp & pA running

• Lighter ions @ higher luminosity.

• Beginning 2007


conclusions

• HI in LHC: a rigorous step towards the QGP physics

– Perturbative + weak coupling methods– Direct partonic probes: Jets.

• The LHC HI dedicated experiment: ALICE– Penetrating and final state probes

• 884 members & 28 countries & 77 institutes• Rendez-vous @ CERN March-April 2007


A new research domain

Quark Matter2002

inNantes

Documents

The h eavy i on c ollider e xperiment @ LHC A L I C E