Hard probes of hot, dense matter at RHIC

Report from PHENIX

2

outline

Introduction to PHENIX & our physics approachTalk covers only a subset of PHENIX results!

Elliptic flow: magnitude and flavor dependence of v2

Jets in pp, dAu and AuAuSuppression and non-suppressionpT distribution of partonsa closer look at Au+Au

Baryons and jet fragmentation Heavy quark production

3

did something new happen at RHIC?

Study collision dynamics (via final state)

Probe the early (hot) phase

Equilibrium?hadron spectra, yields

Collective behaviori.e. pressure and expansion?elliptic, radial flow

vacuum

QGP

Particles created early, predictable quantity, interact differently in QGP vs. hadron matterfast quarks/gluons, J/fast quarks/gluons, J/, D mesons, D mesonsthermal radiation

4

s = 200 GeV, hard probesstart with pQCD & pp collisions

p-p hep-ex/0304038

Good agreementwith NLO pQCD

Works!

A handle on initial NN interactions by scattering of q, g inside N

We also need:2

/( , )

a Nf x Q

2

/( , )ch a

D z Q

Parton distribution functions

Fragmentation functions

0

5

In A+A: QCD in non-perturbative regime

T/Tc

Karsch, Laermann, Peikert ‘99

/T4

we look for physics beyond simple superposition of NN:

EquilibrationCollective effectsEnergy, color transport in dense mediumDeconfinement?

Physics is soft!

EOS

Lattice…

Tc ~ 170 ± 10 MeV (1012 °K)

~ 3 GeV/fm3Lattice QCD says:Create these conditions to look for new physics

6

PHENIX at RHIC

2 Central spectrometers

2 Forward spectrometers

3 Global detectors

7

USA Abilene Christian University, Abilene, TX Brookhaven National Laboratory, Upton, NY University of California - Riverside, Riverside, CA University of Colorado, Boulder, CO Columbia University, Nevis Laboratories, Irvington, NY Florida State University, Tallahassee, FL Georgia State University, Atlanta, GA University of Illinois Urbana Champaign, IL Iowa State University and Ames Laboratory, Ames, IA Los Alamos National Laboratory, Los Alamos, NM Lawrence Livermore National Laboratory, Livermore, CA University of New Mexico, Albuquerque, NM New Mexico State University, Las Cruces, NM Dept. of Chemistry, Stony Brook Univ., Stony Brook, NY Dept. Phys. and Astronomy, Stony Brook Univ., Stony Brook, NY Oak Ridge National Laboratory, Oak Ridge, TN University of Tennessee, Knoxville, TN Vanderbilt University, Nashville, TN

Brazil University of São Paulo, São PauloChina Academia Sinica, Taipei, Taiwan China Institute of Atomic Energy, Beijing Peking University, BeijingFrance LPC, University de Clermont-Ferrand, Clermont-Ferrand Dapnia, CEA Saclay, Gif-sur-Yvette IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, Orsay LLR, Ecòle Polytechnique, CNRS-IN2P3, Palaiseau SUBATECH, Ecòle des Mines at Nantes, NantesGermany University of Münster, MünsterHungary Central Research Institute for Physics (KFKI), Budapest Debrecen University, Debrecen Eötvös Loránd University (ELTE), Budapest India Banaras Hindu University, Banaras Bhabha Atomic Research Centre, BombayIsrael Weizmann Institute, RehovotJapan Center for Nuclear Study, University of Tokyo, Tokyo Hiroshima University, Higashi-Hiroshima KEK, Institute for High Energy Physics, Tsukuba Kyoto University, Kyoto Nagasaki Institute of Applied Science, Nagasaki RIKEN, Institute for Physical and Chemical Research, Wako RIKEN-BNL Research Center, Upton, NY University of Tokyo, Bunkyo-ku, Tokyo Tokyo Institute of Technology, Tokyo University of Tsukuba, Tsukuba Waseda University, Tokyo S. Korea Cyclotron Application Laboratory, KAERI, Seoul Kangnung National University, Kangnung Korea University, Seoul Myong Ji University, Yongin City System Electronics Laboratory, Seoul Nat. University, Seoul Yonsei University, SeoulRussia Institute of High Energy Physics, Protovino Joint Institute for Nuclear Research, Dubna Kurchatov Institute, Moscow PNPI, St. Petersburg Nuclear Physics Institute, St. Petersburg St. Petersburg State Technical University, St. PetersburgSweden Lund University, Lund

12 Countries; 57 Institutions; 460 Participants

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Is the energy density high enough?PRL87, 052301 (2001)

R2

2c

Colliding system expands:

dy

dE

cRT

Bj 22

11

02

Energy tobeam direction

per unitvelocity || to beam

5.5 GeV/fm3 (200 GeV Au+Au)

well above predicted transition!

9

pQCD in Au+Au? direct photons

[w/ the real suppression]

( pQCD x Ncoll) / background Vogelsang/CTEQ6

[if there were no suppression]

( pQCD x Ncoll) / ( background x Ncoll)

Au+Au 200 GeV/A: 10% most central collisions

[]measured / []background = measured/background

Preliminary

At high pT, it also works!

TOT

pT (GeV/c)

10

Pressure? “elliptic flow” barometer

Origin: spatial anisotropy of the system when created, followed by multiple scattering of particles in the evolving system spatial anisotropy momentum anisotropy

v2: 2nd harmonic Fourier coefficient in azimuthal distribution of particles with respect to the reaction plane

Almond shape overlap region in coordinate space

y2 x2 y2 x2

2cos2 vx

y

p

patan

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PHENIX measures v2 two ways:

2 particle correlationsGets tricky at high pT,

jets can contribute

Determine reaction plane at y = 3-4From BBC, with full

azimuthal symmetryMeasure hadrons in

central arms, sort vs. reaction plane

No jet effects upon found reaction plane

min bias 200 GeV Au+ Au

12

Implication #1 of fast equilibration & large v2Huge cross sections!!

13

Implication #2 (from flavor dependence)nucl-ex/0305013

above p forpT < 2 GeV/c.Then crosses over

Values ~ saturateat high pT

geometry?

v2/quark seemsalmost constant create hadronsby coalescence of quarks from boosted distribution?

14

a unique probe for physics of hot medium

hadrons

q

q

hadronsleadingparticle

leading particle

schematic view of jet productionProbe: Jets from hard scattered quarks

Observed via fast leading particles orazimuthal correlations between the leadingparticles

But, before they create jets, the scattered quarks radiate energy (~ GeV/fm) in the colored medium

decreases their momentum (fewer high pT particles)“kills” jet partner on other side “jet quenching”

15

Nuclear Modification of Leading Part. Spectra?

ddpdT

ddpNdpR

TNN

AA

TAA

TAA /

/)(

2

2

<Nbinary>/inelp+p

nucleon-nucleon cross section

1. Compare Au+Au to nucleon-nucleon cross sections2. Compare Au+Au central/peripheral

Nuclear Modification Factor:

If no “effects”: RAA < 1 in regime of soft physics RAA = 1 at high-pT where hard scattering dominates Suppression: RAA < 1 at high-pT

AA

AA

AA

16

pp

AuAubinaryAuAuAA Yield

NYieldR

/

2/pp

AuAupartAuAupartAA Yield

NYieldR

/

Au-Au s = 200 GeV: high pT suppression!

PRL91, 072301(2003)

17

Suppression: a final state effect?

Hadronic absorption of fragments: Gallmeister, et al. PRC67,044905(2003)Fragments formed inside hadronic medium

Energy loss of partons in dense matterGyulassy, Wang, Vitev, Baier, Wiedemann…

PCM & clust. hadronization

NFD

NFD & hadronic TM

PCM & hadronic TM

CYM & LGT

string & hadronic TM

Hadron gas

1AuAuR Absent in d+Au collisions!d+Au is the “control” experiment

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Suppression: an initial state effect?

Gluon Saturation (color glass condensate)

Wavefunction of low x gluons overlap; the self-coupling gluons fuse, saturating the density of

gluons in the initial state. (gets Nch right!)

• Initial state elastic scattering (Cronin effect) Wang, Kopeliovich, Levai, Accardi

• Nuclear shadowing

Levin, Ryshkin, Mueller, Qiu, Kharzeev, McLerran, Venugopalan,

Balitsky, Kovchegov, Kovner, Iancu …

probe rest frame

r/ggg

dAu AuAuR R RdAu~ 0.5D.Kharzeev et al., hep-ph/0210033

1dAuR

decreases dAuR

Broaden pT :

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Compare centrality dependence to control

Dramatically different and opposite centrality evolution of AuAu experiment from dAu control.

Jet suppression is clearly a final state effect.

Au + Au Experiment d + Au Control

20

Centrality dependence of Cronin effect

Probe response of cold nuclear matter with increased number of collisions.

See larger Cronin effect for baryons than for mesons (as at Fermilab)

Qualitative agreement with model by Accardi and Gyulassy. Partonic Glauber-Eikonal approach: sequential multiple partonic collisions. nucl-th/0308029

21

Pions in 3 detectors.

Charged pions from TOF

Neutral pions from EMCAL

Charged pions from RICH+EMCAL

Cronin effect gone at pT ~ 8 GeV/c

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Does Cronin enhancement saturate?

A different approach:

Intrinsic momentum broadening in the excited projectile proton:

hpA: average number of collisions:

X.N.Wang, Phys.Rev.C 61 (2000): no upper limit.

Zhang, Fai, Papp, Barnafoldi & Levai, Phys.Rev.C 65 (2002): n=4 due to proton d dissociation.

23

Jet physics in PHENIXTrigger: hadron with pT > 2.5 GeV/c

Count associated particles for each trigger at lower pT (> 1 GeV/c) “conditional yield”

Near side yield: number of jet associated particles from same jet in specified pT bin

Away side yield: jet fragments from opposing jet

Intra-jet pairs angular width :

N |jTy|

Inter-jet pairs angular width :

F |jTy| |kTy|

trigger“near side” < 90° jet partner

“away side” > 90° opposing jet

CARTOON

flow

flow+jet

NF

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Questions we can ask

What is the intrinsic (primordial) parton transverse momentum kT?

In a nucleon? Nucleus?Defines baseline for modifications

What is the fragmentation function?Shape & width, defined by jT, in p+p collisionsFlavor composition of fragments, to compare observed

baryon/meson yields in Au+Au

vital for understanding of mechanism of parton interaction with QCD medium formed at RHIC

25

jet fragmentation and momentum

2 2 21 1 2cos tan tan

2N N

y Fk pk

|jy| = mean transverse momentum of the hadron with respect to the jet axis (in the plane to beam axis)

21sin N

yj j p

|ky| = mean effective transverse momentum of the two colliding partons in the plane to beam axis

vac IS nuc2

l2 2 2

FS nuclk k kk

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pp and dAu correlation functions

2.2<pT<6.01<pT<1.5

Fit = const + Gauss(0)+Gauss()

p+p

h+- correl.

d+Au

: 5<pT <16 GeV/c

assoc. with h+-

Near angle peak

Far angle peak

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from jet correlations in pp at s = 200GeV

PHENIX preliminary

|jTy| = 36715 MeV/c

z |kTy| = 66050 MeV/c

|kTy| = 920100 MeV/c

PHENIX preliminary

|jTy| = 36715 MeV/c

z |kTy| = 66050 MeV/c

|kTy| = 920100 MeV/c

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Jet cone “width” independent of s *

CCOR CollaborationPhys. Lett. 97B(1980)163

*Subject to same trigger bias by selecting pT of particles

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Au+Au: lost energy is absorbed by medium

Near-side width is constant.Away-side width increases with centrality.

(2.5<pTtrigg<4.0)@ (1.0<pTtrigg<2.5)

flow

flow+jet

NF

30

90° yield

Au+Au conditional yields(Number of particle pairs per trigger particle in AuAu)

The near-side width is independent of centrality.

The away-side width is a strong function of centrality.

But if we integrate the entire Gaussian for the away-side, the away-side associated yields change in step with the near side associated yields as they increase with centrality.

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central Au+Au is very baryon rich!

p/ ~1 at high pT

in central collisionsHigher than in p+por jets in e+e-collisions

nucl-ex/0305036 (PRL)

Hydro. expansion at low pT

+ jet quenching at high pT:Recombination of boosted q’s?Modified fragmentationfunction INSIDE the medium?

Teff = 350 MeV

pQCD spectrum shifted by 2.2 GeV

R. Fries, et al

32

Do the baryons scale with Ncoll?

Baryons appear not suppresed Ncoll at pT = 2 – 4 GeV/c

Au+Au

Yield depends on quark content!Quark recombination…

central

peripheral

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So, are the baryons soft, or from jets?

• Look for jet-like correlations with baryons of pT = 2.5 - 4 GeV/cIdentify trigger particleCount associated particles per trigger

• If baryon excess from quark recombination (coalescence)Expect fewer jet-like associated particles

thermal partons coalescence no partnerSo yield of associated particles should decrease

when coalescence contribution increases with centrality.

34

The data say:

QM04 consensus: coalescence of jet + thermal partons this is medium modification of the jet fragmentation!

• jet partner equally likely for trigger baryons & mesons

• slight decrease of baryon associated particles with centrality!

• expected from recombination

35

Identify Triggers: Away Side Yields

In agreement with other measurements of suppression/broadening

Baryon trigger:more associated particles on far side?

36

ProtonA. Andronic et. Al. Nucl-th/0303036

Deconfinement? Does colored medium screen c+cbar?

EXTRA (thermal) J/no Deconfinement:? J/ above Tc:??

R.L. Thews, M. Schroedter, J. Rafelski Phys. Rev. C63 054905 (2001): Plasma coalesence modelfor T=400MeV and ycharm=1.0,2.0, 3.0 and 4.0.

L. Grandchamp, R. Rapp Nucl.

Phys. A&09, 415 (2002) and Phys. Lett. B 523, 50 (2001):Nuclear Absorption+ absoption in a high temperature quark gluon plasma

40-90%least central Ncoll=45

0-20%most central Ncoll=779

20-40%semi central Ncoll=296

Look at J/nucl-ex/0305030

37

PHENIX PRELIMINARY

Open charm: baseline is p+p collisions

fit p+p data to get the baseline for d+Au and Au+Au.

Measure charm via semi-leptonic decay to e+ & e-

, photon conversions are measured and subtracted

38

Curves are the p+p fit, scaled by the number of binary collisions

No large suppression as for light quarks!

PHENIX PRELIMINARY

39

How about Color Glass Condensate?

Pt (GeV/c) Pt (GeV/c)

Rda

Rda

Peripheral d+Au (like p+p)

Central: Enhancednot suppressed PHENIX preliminary

y=0

Xc(A)

pQCD

BFKL, DGLAP

G-sat.

>2

RHIC

Log Q2

No CGC signalat mid-rapiditySo, perhaps

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But at forward rapidity reach smaller x

y = 3.2 in deuteron direction x 10-3 in Au nucleus

Strong shadowing, maybe even saturation?

d Au

Phenix Preliminary

41

Analysis

Photon cuts: - low energy threshold - |TOF| - 2 (photon-like cluster) - fiducial cut

Asymmetry cut < 0.5

42

Yields in 3 centrality selections 0-20%, 20-60%, 60-92%

Corrected for acceptance, efficiency, and branching ratio

Absolute normalization still being finalized (to present /0)

Errors dominated by uncertainty in peak extraction (point-to-point systematic error)

Yields (shown in arbitrary units) as a function of pT

PHENIX Preliminary

43

Nuclear Modification Factor for (compared to 0)

peripheralbinaryperipheral

centralbinarycentral

NYield

NYield

//

0

RC

P =

PHENIX Preliminary

44

Efficiency beingevaluated

Anti-Penta Quarks with PHENIX?

Statistically it’s a 4 effect1.54 GeV

Systematic Error under study

Nobody scrambles quarks like we do!

- n + K-

45

conclusions

Rapid equilibration! Strong pressure gradients, hydrodynamics worksConstituent scattering cross section is very large

EOS is not hadronic The hot matter is “sticky” – it absorbs energy & seems to

transport it efficientlySee energy loss/jet quenchingd+Au data says: final state, not initial state effect

So, the stuff is dense, hot, ~ equilibrated AND NEW! QGP discovery?

J/ suppression or not? This runTinitial? direct photons & low-mass continuum dileptons

46

Identified Associated Particles--AuAu

Trigger (not identified)

“near side” < 90° jet partner identified

“away side” > 90° opposing jet fragment identified

Perhaps due to PHENIX’s limited acceptance

47

Medium properties

Extract by constraining QCD-inspired models with measured jet suppression and v2

Find (values from Vitev, et al; others consistent)

Energy loss <dE/dz> (GeV/fm) 7-10 0.5 in cold matter

Energy density (GeV/fm3) 14-20 >5.5 from ET data

dN(gluon)/dy ~1000 200-300 at SPS

T (MeV) 380-400 must measure!

Equilibration time0 (fm/c) 0.6 Parton cascade agrees

Medium lifetimeTOT (fm/c) 6-7

48

Implications of the results for QGP

Ample evidence for equilibration v2 & jet quenching measurements constrain initial gluon

density, energy density, and energy loss parton interaction cross sections 50x perturbative

parton correlations at T>Tccomplicates cc bound states as deconfinement probes!

Hadronization by coalescence of thermal,flowing quarksv2 & baryon abundances point to quark recombination

as hadronization mechanismJet data imply must also include recombination between

quarks fromjets and the thermalized medium medium modifies jet fragmentation!

49

J/ in pp and d+Au

● Total cross section :

BR pp = 159 nb ± 8.5 % (fit) ± 12.3% (abs)

50

dAu/pp versus rapidity

51

Vogt, nucl-th/0305046Kopeliovich, hep-ph/0104256

● x2 is the momentum fraction of

the parton from the Au nucleus.

● Data favours (weak) shadowing + (weak) absorption ( > 0.92)

● With limited statistics, difficult to disentangle small nuclear effects.

Low x2(shadowing region)

dAu/pp versus rapidity

See R. G. de Cassagnac's talk Friday parallel 2

52

formulae

However, if we neglect the fragmentation momentum |jTy| one can see that the F is a measure of ztrigg |kTy|. In order to extract the |kTy| one has to know also the fractional momentum of the trigger particle ztrigg.

53

Fragmentation function

If the kTy pT,trigg than xE measures directly

the slope of the fragmentation function D(z) = prop exp…

54

xE in pp collisions

CCOR see ref….PHENIX preliminary

Correct +-

55

z extracted from pp dataz

trig

g

1

z

PHENIX preliminary PHENIX preliminary

56

PHENIX PRELIMINARY

PHENIX PRELIMINARYPHENIX PRELIMINARY

PHENIX PRELIMINARY

d+Au data vs centrality

The curves are the p+p fit, binary scaled.

57

The yellow band represents the set of alpha values consistent with the data at the 90% Confidence Level.

Au+Au dN/dy, binary scaled

See Sean Kelly's talk Thursday parallel 2

58

Peripheral Au-Au like p-p and d-Au

h/0 ratio shows that p is enhanced only < 5 GeV/c

59

How to get 50 times pQCD ?

• Lattice indicates that hadrons don’t all melt at Tc!c bound at 1.5 Tc Asakawa &

Hatsuda, PRL92, 012001 (2004)

charmonium bound states up to ~ 1.7 Tc Karsch; Asakawa&Hatsuda

, survive as resonances Schaefer & Shuryak, PLB 356 , 147(1995)

q,g have thermal masses at high T. s runs up at T>Tc? (Shuryak and Zahed)would cause strong rescattering

qq meson

spectral function

60

E. Shuryak

61

Implication #3:

Hydro can reproduce magnitudeof elliptic flow for , p at low pT

BUTmust add QGP to hadronic EOS!!

Similar conclusion reached byKo, Kapusta, Bleicher, Molnar others… rescattering must be very large!

Kolb, et al.

62

Why no energy loss for charm quarks?

“dead cone” predicted by Kharzeev and Dokshitzer, Phys. Lett. B519, 199 (1991)

Gluon bremsstrahlung:kT

2 = 2 tform/transverse momentum of radiated gluon

pT in single scatt. mean free path

~ kT / gluon energy But radiation is suppressed below angles 0= Mq/Eq

soft gluon distribution is

dP = sCF/ d/ kT2 dkT

2/(kT2+ 2 0

2) 2not small forheavy quarks!causes a dead cone

63

Why a liquid?

Mean free path is very shortSmaller than size of systemMust be so to get large energy loss

Interaction among gluons is quite strong

Have a (residual) correlation among partons until T>>Tc

64

Hydro describes single + multi-particles

• How to increase R without increasing Rout/Rside???

EOS?initial T & r profiles? emissivity?

Maybe an experimental artifact (i.e. Coulomb corrections) ?

But FAILS to reproducetwo-particle correlations!

65

Need partial Coulomb correction?

Full CoulombNo Coulomb

RlongRside λRout

R [

fm],

λ (

x10)

Long-lived resonance contribution• Full Coulomb correction on all pion pairs assuming well localized (core) source ~5fm.•pions from resonance decays come from a larger “halo” source, and have weaker (negligible) Coulomb effect.

fPC dependence of Bertsch-Pratt radii• Vary the fraction (fPC) of Coulomb corrected pairs from 0 (no Coulomb) to 1 (full Coulomb).• Rside and Rlong decrease as fPC is reduced.• In contrast, Rout increase as fPC is reduced. • The ratio Rout/Rside is very sensitive to fPC .

0 0.2 0.4 0.6 0.8 1.0fPC

Halo

Core

66

This recent analysis shows the change in Rout

/Rside

when the partial Coulomb correction is used instead of the full Coulomb correction.

The ratio moves in the direction of the models, but only increases to about one. Note the large k

T reach of the data. See Mike Heffner's talk for

detailed discussion of this and other HBT topics.

Rout

/Rside

from HBT

See Mike Heffner's talk Tuesday parallel 3

67

PHENIX looks for J/ e+e- and

There is the electron.

need electron / pion separation at the level of one in 10,000 (needle in a haystack!)

Ring Imaging Cherenkovcounter to tag electrons“RICH”

See signal whenvpart. > cmedium

68

Forward n tagged d+Au

p

n ZDC

Neutron tagged eventsenhance peripheral collisions

<Ncoll> = 5.0 / 3.6Could be Ncoll dependenced+Au looks very similar to p+Au

69

Centrality selection

In PHENIX “min bias” = 92% of geometric cross sectionUse Glauber model to calculate Npart

70

More on RdAu & Glauber calculation

What we actually doRdA= 1/Nevt d2Nparticle/ddpT

--------------------------------- <Ncoll>/pp,inel d2pp/ddpT

TheoreticallyRdA= 1/Nevt d2Nparticle,dAu/ddpT

--------------------------------- <TAB> d2pp /ddpT

As pointed out in nucl-th/0306044<Ncoll> = <TAB>* pp,inel ---------------------

1 – exp (- <TAB>* pp,inel )

We measure pp= 21.3mb

Evaluate trigger eff. for

full pp,inel and correct

particle yield by that

= 0.99982 for m.b.= 0.973 for leading n(absorbed in syst)

71

0 RAA vs. predictions

PHENIX Preliminary

shadowing

anti-shadowing

Theoretical predictions:

d+Au: I. Vitev, nucl-th/0302002 and private communication.

Au+Au: I. Vitev and M. Gyulassy, hep-ph/0208108, to appear in Nucl. Phys. A; M. Gyulassy, P. Levai and I. Vitev, Nucl. Phys. B 594, p. 371 (2001).

Initial state: mult. scatt.,shadowing + final state dE/dx (Au+Au)

Also: Kopeliovich, et al (PRL88, 232303,2002)

predict RpA~1.1 max at pT=2.5 GeV projectile as color dipole

72

Why no big energy loss for heavy quarks?

no x4 suppressionfrom peripheral to central,as predicted fordE/dx=-0.5GeV/fm!

But (we squirm) - Is 40-70% peripheral enough? error bars still big!

73

Jet Evidence in Azimuthal Correlations at RHIC

near-side correlation of charged tracks (STAR)trigger particle pT = 4-6 GeV/c distribution for pT > 2 GeV/c

signature of jets

also seen in (0) triggered events (PHENIX)trigger particle pT > 2.5 GeV/c distribution for pT = 2-4 GeV/c

M. Chiu, PHENIX Parallel Saturday

QM2002 summary slide (Peitzmann)

74

Identifying Jets - Angular Correlations

Remove soft background by subtraction of mixed event distribution

Fit remainder:Jet correlation in ; shape taken from PYTHIAAdditional v2 component to correct flow effects

PHENIX Preliminaryraw differential yields

2-4 GeV

75

Verify PYTHIA using p+p collisions

(neutral E>2.5 GeV + 1-2 GeV/c charged partner)

||<.35 ||>.35

ake cuts in to enhance near or far-side correlationsBlue = PYTHIA

76

In Au+Au collisions

1-2 GeV partner

(neutral E>2.5 GeV + charged partner)

||<.35 ||>.35

1/N

trig d

N/d

1/N

trig d

N/d

Correlation after mixed event background subtraction

Clear jet signal in Au + AuDifferent away side effect than in p+p

77

Jet strengthSee non-zero jet strength as partner pT increases!

jets or flow correlations? fit pythia + 2v2vjcos(2)

partner = .3-.6 GeV .6-1.0 GeV/c 2-4 GeV/c

1/N

trig d

N/d

v2vj

1-2 GeV/c

78

How do high pT yields scale?

vs. binary collisions:continuous decrease as

function of centralityfactor ~ 3.5 from

peripheral to central vs. participants:

first increase, then decrease as function of centrality

for Npart > 100 have 3 change (scaling or no?)

surface emission? re-interactions?accident?

18% scaling uncertainty from corrections

79

Opaque, expanding source would mean:

2222222 2)()( xtso YXRR

)(outX

)(sideY

29.13

5)(

)(

spheres

shellhalfs

R

R

65.012

5)(

)(

sphereo

shellhalfo

R

R

Opaque Expanding

Rischke RIKEN workshop (2002): Such strong xt correlations probably require a lack of boost-invariance...

80

Energy Dependence

Assumptions:in Lab in C.M.

Energy density (Bjorken):

2% most central at sNN=200 GeV:

5.5 GeV/fm3

From AGS, SPS to RHIC:

Transverse energy and charged particle multiplicity densities per participant consistent with logarithmic behaviour

d

dX

dy

dX

d

dX

dy

dX2.1

dy

dE

Rt

2

1

cfm

AfmR

/1

18.1 3/1

PHENIX preliminary

PHENIX preliminary

81

So, is there jet quenching?

Suppression observed to 8 GeV/c! (in 3 independent measurements)

Theory agrees with data when quark, gluon energy loss is included

NB: 2 examples here, others also must add some kind of medium modification of the fast quarks/gluons

In initial or final state?

82

Look at “transverse mass” mT2 = pT

2 + m02

— is distribution e-E/T?i.e. Boltzmann distribution from thermalized gas?

hadron spectra: , K, p and antiprotons

130GeV/A

yes !

Protons are flatter velocity boost to beamResult of pressure built up

83

Note pbar/p behavior

Centrality dependence only for pT > 3 GeV/c

Peripheral collisions have quite a few protons at mid-y

84

Phenix-Star comparison

STAR

Compare for charged hadrons at = 0 in min bias collisionsBoth compare to their own measured pp at s = 200 GeV

85

Are the RdA numbers wrong due to inel?

STAR

Compare for charged hadrons at = 0 in min bias collisionsBoth compare to their own measured pp at s = 200 GeV

PHENIX sees ~10% of single diffractive and 30% of double diffractive in ppAnalysis approach: correct pp to 42 mb via trigger efficiency correction; use =42mb to calculate Ncoll in d+Au~ same as <T(dAu)>* ppmeas in denominator

STAR triggers on forward n, sees all double diffractive and some single diffractive.

No room for PHENIX by 20-30% and STAR by 10%

86

Collide heavy ions at RHIC to

Create very high temperature and density matteras existed ~1 sec after the Big Banginter-hadron distances comparable to that in neutron starscollide heavy ions to achieve maximum volume

Study the hot, dense mediumis thermal equilibrium reached?transport properties? equation of state?do the nuclei dissolve into a quark gluon plasma?

Au + Au at s = 200 GeV/nucleon pairp+p and d+A to compareAlso polarized p+p collisions to study carriers of p’s spin

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We follow history of heavy ion collisions

PCM & clust. hadronization

NFD

NFD & hadronic TM

PCM & hadronic TM

CYM & LGT

string & hadronic TM

, e+e-,

+c,cbar

KpndReal and virtual photons from q scattering sensitive to the early stages. Probe also with q and g produced early, & passing through the medium on their way out.

Hadrons reflect medium properties when inelastic collisions stop (chemical then thermal freeze-out).

high , pressure builds up

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Grows with s as expected

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charm by single e production

Cross section fits into expected energy dependence

130 GeV/A Au+Au

Phys.Rev.Lett. 88 (2002) 192303

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25 Juin 2003

Central/peripheral versus Ncoll

• First measurement of J/ vs

Ncoll in pA(dA)!

• Low and med x2 have small

variation with Ncoll

– Weak nuclear effects

• High x2 has a steep rising

shape - no clear explanation

at present, see

High x2

Low x2