Gabor David QM01

Miklos Gyulassy (Collegium Budapest/Columbia U)

Adapted from Axel Drees , X.N. Wang, W.Zajc, and G. David Talks at QM2001

First Hints for Jet Quenching at RHIC

Introduction

p-p and p-A collisions

CERN high pT results

First data from RHIC

Status

* Hard vs Soft QCD

* Cronin Enhancement

* WA98 No Quench?

* Incredible!!

Bibliography

1. Quark Matter 2001, SUNY Stony Brook, Jan. 15-20, 2001 all talks at ftp://woodstock.physics.sunysb.edu/pub/2. X.~Wang and M.~Gyulassy, ``Energy and centrality dependence of rapidity densities at RHIC,'' nucl-th/0008014.3. M.~Gyulassy, I.~Vitev and X.~N.~Wang, ``High $p_T$ azimuthal asymmetry in non-central $A + A$ at RHIC,'' nucl-th/0012092. 4. P.~Levai, G.~Papp, G.~Fai and M.~Gyulassy, ``Kaon and pion ratio probes of jet quenching in nuclear collisions,'' nucl-th/0012017.5 M.~Gyulassy, P.~Levai and I.~Vitev, ``Non-Abelian energy loss at finite opacity,'' Phys.\ Rev.\ Lett.\ {\bf 85}, 5535 (2000), [nucl-th/0005032]; Nucl.\ Phys.\ {\bf B594}, 371 (2001) [nucl-th/0006010]6. X.~Wang and M.~Gyulassy,``Gluon shadowing and jet quenching in A + A collisions at s**(1/2) = 200-GeV,'' Phys.\ Rev.\ Lett.\ {\bf 68}, 1480 (1992); Phys.Rev.D45:844-856,1992, Phys.Rev.D44:3501-3516,1991

Hard vs Soft QCD Dynamics Slow Onset of (semi)hard processes (XNWang & Hwa’89) (Eskola, Landshoff, Lindfors, Kajantie’89)

…

( ) ( )2 [1 ]jet soft NNT binelastic d b e HIJING, VNI, NEXUS

)()()( sss softjetqq

21 2 1 1 2 2

,

1( ) ( )

ˆ2ab

jet aT ba b

ddp dy dy x f x x f x

dt

T 0p >p

XNWang QM01

1) pQCD Resolved Hard Processes

2) Soft (Regge) Phenomenology

0 1 2Tp p GeV

0 1 2Tp p GeV

(XNWang &MG ’91)

Energy dependence of dN/dy in pp

in

jet

jetn

in

jet

jetn

HIJING, NEXUS: Soft Strings dN/dy Const.

jethardsoftnnn

dy

dN

in

jet

jet

n

ppin

ppjet

hardBinarysoftpart

AAch nNnN

d

dN

5.0

AA Collisions

XNWang QM01

First Hints of Mini-Jet Showers in dN/d at RHIC

soft physics

with quenching

No jet quenchingSTARPHENIXBRAHMS

X.N. Wang, MG ‘00

PRL85(00)3100

First Global Hint of Extreme Dense Gluon Plasma ?dN

/d

/ .5N

part

Npart

Centrality Dependence of dNch/d

P. Steinberg QM01

dNgluon/dyHIJING ”glue (0=0.1 fm/c) 10/fm3

dNgluon/dyEKRT ”glue (0=0.1 fm/c) 50/fm3

XNW,MG nucl-th/0008014

nucl-ex/0012008

dET/d

dNch/d

b

Initial Geometry

EZDC

NBBC

Experimental Handles

Determining Collision Impact Parameter and N(participants)

0-5%

5-10%

10-15%15-20%

PHENIX preliminaryPHENIX preliminary

Use combination of cuts on Zero Degree Calorim. and Beam-Beam

Counters or dNch/d or dET/d

to define centrality classes Glauber (Eikonal) geometry modeling

ET

ET

EZDC

NBBC

b

PHENIX Centrality Cuts

24

Conversion to Ncollisions and Nparticpants

5 60%3.7 60%80-92%

19 60%19 60%60-80%

76 15%123 15%30-60%

178 15%383 15%15-30%

271 15%673 15%5-15%

347 15%945 15%0-5%

ParticipantsCollisionsCentrality

Phenix Centrality Selection

W.Zajc QM01

Data available over wide range of s=20-2000 GeV, but not for 130 GeV !

Good power law fit:

d2N/dpt2 = A (p0+pt)

-n

Well Known Inclusive pt-Distributions in p-p

A.Dress QM01

Hard pQCD Probes: Drell-Yan Heavy Quarks (D, Direct Jets, high pT hadrons

Hard Probes In Heavy Ion Collisions

Z

Observables1. dE/dx in QGP jet quenching2. Deconfinement J/suppression

beams of hard probes:jets, J/ ….

Vacuum

QGP

Drell-Yan and Production at CERN/SPS

C. Lourenco NA50 QM01

( ) ( )DY DYA B q q AB pp ( ) ( ) !DY A B c c AB pp

Suppressed even in p+A !!

Results from the SPS

data well described by pQCD + (intrinsic + initial) kT (A,Q) broadenning

data equally well described by hydrodynamic fit

A. Dress QM01

However,No RutherfordPower Law Tail

Extrapolating from pp to AA

hard scattering processes scale with binary collisions:

scale to min. bias Au-Au:

scaling to central collisions: ppAA A 2

2

0

( ) ( )cb

AA c pp AAb b d b T b

pp

min. bias

5% central

2exp

0

( ) ( ) ( | )AA cut pp AA cutdN b d d b T b P b b

( ) ( , )A AT b dz z b

22 2( ) ( ) ( )b b

AB A BT b d s T s T s

Glauber Eikonal Geometry

} 2 4 / 3

2( )pp

A AAA R

T b R

The Cronin Effect

modification of pt spectrum in p-A collisions:

tppA ppA

2

2

2

21

t

pp

t

pApA dp

d

dp

d

AR

AA

Comparing CERN-SPS Pb-Pb to p-p

RAA exhibits amplified Cronin Enhancement at SPS energies

RAA (RpA ) 2

Parton energy loss, if any, is overwhelmed by initial state soft multiple collisions at SPS!

X.N.Wang

AA AA

4

Npart/2Nbin

* dE/dx is small at SPS due to short plasma lifetime and low gluon density MG, P. Levai, I. Vitev, PRL85(00)5535

first high pt data from RHIC: pt range to 6 GeV, covering >6 orders of magnitude well above what was reached at the SPS

Inclusive pt Spectra of charged ParticlesJ.C. Dunlop, STARF. Messer, PHENIX

A.Dress QM01

G. David, PHENIXF. Messer, PHENIXJ.Velkovska, PHENIX

0 from 1 to 4 GeV

good agreement with h- below 2 GeV

agreement in shape with from 0.3 to 2.2 GeV

Preliminary PHENIX Inclusive pt Spectra of Pions and h

Puzzle:What flavorHadrons surviveAt high pT?

Preliminary PHENIX Hint that pbar >

Spectacular Quench of Pions Why do baryons survive? Baryonium Matter pT> 2 GeV?

F. Messer, PHENIXJ.Velkovska, PHENIX

H.Ohnishi, PHENIX

??

A. Dress QM01

Preliminary Centrality Dependence of pt Spectra

F. Messer, PHENIX

A. Dress QM01

G.David, PHENIX

Centrality dependence: complete systematics for charged central and peripheral for

Comparison to p-p central collisions below p-p extrapolation peripheral agree reasonably with p-p extrapolation

(**note systematic uncertainty ~60% due to Ncoll)

Preliminary Quenching Pattern in central Au-Au

Use identical p-p parameterization for all data sets normalize data to number of binary collisions divide by p-p parameterization UA1(130)/42 mb

Characteristic features: increases up to ~ 2 GeV saturates at RAA < 1 decrease at high pt

Issues: large systematic error ~ 30% data: normalization, differences in shape, centrality selection, flavor .. systematic uncertainty of p-p parameterization

A. Dress QM01

Comparison with pQCD

P.Levai, G. Fai, G. Papp, MG (QM01)

Peripheral CollisionsFollow simple pQCD

Central CollisionsRequire MediumDependent pQCD

Very High GluonPlasma OpacityL/EGLV/Eglue

P.Levai, G. Fai, G. Papp, MG (QM01)

Cronin Enhancement vs Jet Quenching

CroninEnhancement

dEGLV/dxQuench

Azimuthal Asymmetries in Non-Central Collisions

Almond shape overlap region in coordinate space

y2 x2 y2 x2

2cos2 v

Momentum spacex

y

p

patan

P. Jacobs and G. Cooper, nucl-ex/0008015

Raimond Snellings QM01

22/ 1 2v ( ) cos 2T TdN dydp d p 2/ 1 2 ( ) cos 2dN dzdrd r

Preliminary STAR charged particle anisotropy pt < 4.5 GeV/c vs Hydrodynamcs

Only statistical errors Systematic error 10% - 20%

for pt = 2 – 4.5 GeV/c

Raimond Snellings QM01

Saturated pT> 2GeV

22/ 1 2v ( ) cos 2T TdN dydp d p

Huge Asymmetry !

1.32 0.7(0) / ( ) 2dN dN

Preliminary STAR Charged particle anisotropy

Raimond Snellings, STAR systm. error 10% - 20% for pt = 2 – 4.5 GeV/c

Kolb et al (Hydro) + MG, P. Levai, I.Vitev (dEQCD/dx) PRL85(00)5535

MG, I.Vitev and X.N. Wang, nucl-th/00012092, PRL in press

Constraint on dE/dx glue dNglue/dy 2

2/ 1 2v ( ) cos 2T TdN dydp d p

Differential v2(pT): Hydro up to ~1.5 GeV followed by saturation

Constraint on Initial Conditions: dNglue/dy > 500 Is This consistent with Single Inclusive Quenching?

STAR: Phys.Rev.Lett.86(01)402

Comparison with pt distribution

calculation compatible with anisotropy measurement and pt - spectra

Hydro+GLV: M. Gyulassy, I. Vitev and X.N. Wang, nucl-th/00012092

Summary Only 4 months after the first 3 week run at RHIC

PHENIX and STAR reported striking new high-pt data at QM01

for charged and identified particles pt spectra to 4 - 6 GeV

azimuthal angular correlation out to 4.5 GeV

Peripheral collisions are well reproduced by pQCD (TAB scaled pp) Central collisions show clear deviation from scaled p-p extrapolation

While Premature to draw definite or quantitative conclusions

it appears (to me) that a (gluon) plasma with at least

100 times nuclear matter density was produced in Au+Au at Ecm=130 AGeV RHIC run 2001: Vastly higher statistics with both Au+Au and p+p at Ecm=200 AGeV will probe out to pT>10 GeV

high-pt data are consistent with “jet quenching” predictions !

A phase transition as seen from CERN

- the skier can move further … a new phase develops

- A skier (quark) isconfined inside snowpatches (hadrons)

- the skier (quark ?)can move freelyover long distances …

Luciano Maiani, CERN February 2000

- A skier (quark jet) easily passes through cold, color white snow(a hadronic medium)

-At higher energies some of snow melts and jets have harder time getting to lodge(the mixed phase)

-At RHIC the snowmelts. Skiers (and jets) break their legs passing through opaque colorful matter(the QGP)

M.G., KFKI February 2001

A phase transition as seen by jet at RHIC