John Harris (Yale) LHC Conference, Vienna, Austria, 15 July 2004 Heavy Ions - Phenomenology and...

John Harris (Yale) LHC Conference, Vienna, Austria, 15 July 2004

Heavy Ions - Phenomenology and Status

LHC

• Introduction to Rel. Heavy Ion Physics• The Relativistic Heavy Ion Collider (RHIC)• Creating Hot Bulk QCD Matter• Using Hard Scattering to Probe the Matter• Conclusions & Expectations


Early Universe

National Geographic(1994)

&Michael Turner

quark-hadronphase transition2 x 1012 Kelvin


Lattice QCD at Finite Temperature

F. Karsch, et al.Nucl. Phys. B605 (2001) 579

mu,d= ms

mu = md

ms mu,d

Action density in 3 quark system in full QCDH. Ichie et al., hep-lat/0212036

G. Schierholz et al., Confinement 2003

Heavy quarks suppressed exp(-mc,b,t/T)TC ~ 175 8 MeV C ~ 0.3 - 1 GeV/fm3


Hot Bulk QCD Matter (QGP)• Standard Model Lattice Gauge Calculations predict

Deconfinement phase transition at high T in QCD

• Cosmology Quark-hadron phase transition in early Universe• Astrophysics Cores of dense stars

• Establish bulk properties of QCD at high T and density

• Can we make it in the lab?


Relativistic Heavy Ion Collider

STARPHENIX

PHOBOS BRAHMS

RHIC

Design Performance Au + Au p + pMax snn 200 GeV 500 GeVL [cm-2 s -1 ] 2 x 1026 1.4 x 1031

Interaction rates 1.4 x 103 s -1 3 x 105 s -1

Two Concentric Superconducting Rings

Ions: A = 1 ~ 200, pp, pA, AA, AB


Relativistic Heavy Ion Collider and Experiments

STARSTAR


Space-time Evolution of RHIC Collisions

e

space

time jet

Hard Scattering + Thermalization (< 1 fm/c)

AuAu

Exp

ansio

n

Hadronization

p K

Freeze-out(~ 10 fm/c)

QGP (~ few fm/c)

e


What Can We Learn from Hadrons at RHIC?• Can we learn about Hot Nuclear Matter?

– Equilibration? Thermodynamic properties?– Equation of State?– How to determine its properties?

• Hadron Spectrum

Soft Physics reflect bulk properties (pT < 2 GeV/c( )99% o f

hadrons)

Hard Scattering & Heavy Quarks probe the medium


What Have We Learned at RHIC So Far?

Large energy densities dn/ddET/d GeV/fm3

x nuclear densityCollective phenomena: Large elliptic flow Extreme early pressure gradients & energy densities

Hydrodynamic & requires quark-gluon equation of state!

Global observations: Large produced particle multiplicities dnch/d |=0 = 670, Ntotal ~ 7500 15,000 q +q in final state, > 92% are produced quarks

Quark coalescence / recombination & flow constituent quark degrees of freedom


Elliptic Flow Early Pressure in System

x

z

y

Initial Ellipticity(coord. space)

ReactionPlane (xz)

Sufficient interactions early (~ 1 fm/c) in system to respond to early pressure? before self-quench (insufficient interactions)?

System able to convert original spatial ellipticity into momentum anisotropy?

Sensitive to early dynamics of initial system

p

p

Azimuthal anisotropy(momentum space)

?

) FlowElliptic

2cos2 FlowDirected

cos2 Isotropic

1 ( 21

21

2

3

3

RPRPtt

vvdydpp

dpd

dE

x

y

pp

atan


Large Elliptic Flow Observed• Azimuthal asymmetry of charged

particles: dn/d ~ 1 + 2 v2(pT) cos (2) + ...

x

z

y

Particle mass dependence of v2

requires

• Early thermalization

• Ideal hydrodynamics • Quark-gluon Equation of State


Quark Recombination and Elliptic FlowComplicated v2(pT) flow pattern is observed for identified hadrons

d2n/dpTd ~ 1 + 2 v2(pT) cos (2 )If the flow is established at the quark level, it is predicted to be simple when pT → pT / n , v2 → v2 / n , n = (2, 3 quarks) for (meson, baryon)

15000 quarks flow collectively


More Data on v2 and Quark Recombination

• e.g. take strange particle v2• v2 of all hadrons obey quark recombination systematics!

Au+Au sNN=200 GeVSTAR Preliminary

MinBias 0-80%


What Have We Learned at RHIC So Far?


x nuclear densityCollective phenomena: Large elliptic flow Extreme early pressure gradients & gluon densities

quark-gluon equation of state!

Global observations: Large produced particle multiplicities dnch/d |=0 = 670, Ntotal ~ 7500 15,000 quarks in final state, > 92% are produced quarks

“Chemical” equilibration (particle yields & ratios): Particles yields represent equilibrium abundances

universal hadronization temperature



• Chemically and thermally equilibrated fireball at one temperature T and one ( baryon) chemical potential : – One ratio (e.g., p / p ) determines / T :– Second ratio (e.g., K / ) provides T

• Then all hadronic yields and ratios determined:

Particle Ratios Chemical Equilibrium Temperature

pdedn E 3/)(~ Tμ

TμTμ

Tμ/2

/)(

/)(

eee

pp

E

E

Ratios equilibrium values


Soft Sector (Bulk Dynamics) -What We Have Learned at RHIC!


x nuclear densityCollective phenomena: Large elliptic flow Extreme early pressure gradients & gluon densities

quark-gluon equation of state!

Global observations: Large produced particle multiplicities dnch/d |=0 = 670, Ntotal ~ 7500 15,000 quarks in final state, > 92% are produced quarks

“Chemical” equilibration (particle yields & ratios): Particles yields represent equilibrium abundances

universal hadronization temperature


Small net baryon density K+/K-,B/B ratios) B ~ 25 - 40 MeV Chemical Freezeout Conditions T = 177 MeV, B = 29 MeV T ~ Tcritical (QCD)

“Thermal” equilibration (particle spectra) : Thermal freezeout + large transverse flowTFO = 100-110 MeV, T = 0.5 – 0.6c


Hard Scattering to Probe the Hot Bulk QCD Medium

hadrons

leading particle

hadronsleading particle


Inclusive Hadron pt-spectra: s = 200 GeV AuAu

power law: pp = d2N/dpt

2 = A (p0+pt)-n

Preliminary

STAR


Hadron Spectra: Comparison of AA to NN

Nuclear Modification Factor RAA:AA = Nucleus-NucleusNN = Nucleon-Nucleon

ddpdT

ddpNdpRT

NNAA

TAA

TAA //)( 2

2

Nuclear overlap integral:# binary NN collisions / inelastic NN cross section

NN cross section

AA cross section

AA

(pQCD)

Parton energy loss R < 1 at large Pt


Suppression of High Transverse Momentum Hadrons at RHIC• Large transverse momentum hadrons are suppressed in central

collisions at RHIC

√snn = 17.3 GeV

√snn = 63 GeV

√snn = 130 GeV

by factor ~ 4 - 5 in central collisionsat RHIC


Centrality Dependence of Suppression at RHICAu+Au130 GeV

Phys. Rev. Lett. 89, 202301 (2002)STAR


Is Origin of Suppression Initial or Final State?

Final stateparton energy

loss?

A + A collisions in medium:

gluon saturation?

nuclear effects in initial state

Initial state

no partonenergy loss

nuclear effects in initial state

gluon saturation?p,d + A collisions -

no medium

Distinguish effects -initial statefinal state


Final State Suppression / Initial State Enhancement!• The hadron spectra at RHIC from p-p, Au-Au

and d-Au collisions establish existence of a new final-state effect - early parton energy loss – from strongly interacting, dense matter in central Au-Au collisions

Au + Au Experiment d + Au Control Experiment

Preliminary DataFinal Data


Extreme Energy Densities! – Au-Au suppression

(I. Vitev and M. Gyulassy, hep-ph/0208108)– d-Au enhancement (I. Vitev, nucl-th/0302002 )

understood in an approach that combines multiple scattering with absorption in a dense partonic medium

high pT probesrequire

dNg/dy ~ 1100

> 100 0 Au-Au

d-Au

Au + Au


Hard Scattering (Jets & Leading Particles)as a Probe of Dense Matter

Jet event in eecollision STAR p + p jet event

Can we see jets in high energy Au+Au?

STAR Au+Au (jet?) event


Au+Au Leading Particle (Jet) Azimuthal Correlations

Assume:Au+Au event with high pT particle is a superposition of

p+p event w. high pT particle + AuAu event w. elliptic flow

– v2 from reaction plane analysis

– A from fit in non-jet region (0.75 < || < 2.24)

C2(Au Au) C2(p p) A * (1 2v22 cos(2))

Peripheral Au + Au

Away-side jet

STAR 200 GeV/cperipheral & central Au+Au

p+p minimum bias4<pT(trig)<6 GeV/c

2<pT(assoc.)<pT(trig)Central Au + Au

disappears


Path Length Dependence of “Di-jet” Topologies

y

x

pTtrigger=4-6 GeV/c, 2<pT

associated<pTtrigger, ||<1

in-plane

Out-of-plane

Back-to-back suppression out-of-plane stronger than in-plane


Hammering the Nail in the Coffin

Pedestal&flow subtracted

no jet quenching!

d + Au “di-jet” correlations similar to p + p

Au + Au away-side correlation quenched!

Quenching of Away-side “jet” is final state effect


Hard Scattering Comments

High Pt hadrons suppressed in central Au + Au enhanced in d + AuBack-to-back Jets Di-jets in p + p, d + Au

(all centralities) Away-side jets quenched

in central Au + Auemission from surfacestrongly interacting medium

x


Summary - What Have We Learned at RHIC So Far?

Quark coalescence /flow constituent quark degrees

of freedom

Extreme initial densities – 5 GeV/fm3

~ 30 - 100 x nuclear density

> 15,000 q +q in final state

Equilibrium abundances – Universal hadronization T ~ Tcrit

Rapid u, d, s equilibration near Tcrit

parton E loss – large gluon densities opaque!

Ideal hydro - Early thermalization & quark-gluon EOS

Pedestal&flow subtracted

parton E loss – large gluon densities opaque!

Indicates strongly interacting, bulk QCD-matter formed in RHIC collisions

PRL 91 072305 (2003)Initial state gluon saturation (color glass condensate?) - forward rapidities low-x d+Au is suppressed


Still to do!

RAA d 2N AA dydpT

d 2N pp dydpT NcollAA

Deconfined QGP?cc, bb suppression & melting sequence Strangeness enhancement?

Thermalized? Open charm, beauty, multiply-strange baryon production & flow

Establish properties of the QCD mediumProbe parton E-loss with higher pT triggers, jets, -jetFlavor dependence of suppression & propagationLight vector mesons (mass and width modifications)

Direct Photon Radiation?New phenomena…….LHC! RHIC II!

“the adventure continues!”

John Harris (Yale) Hadron Collider Conference, East Lansing MI, 6/14/04

Still the beginning

Date post:	17-Jan-2018
Category:	Documents
Upload:	ambrose-wilkinson
View:	216 times
Download:	0 times

John Harris (Yale) LHC Conference, Vienna, Austria, 15 July 2004 Heavy Ions - Phenomenology and...

Documents