The PHENIX White Paper

STAR collaboration meeting

2

outline

Introduction to PHENIX & our physics approach Energy density Thermalization & Collectivity High pT phenomena

jet quenching and binary scaling of high pT , charm Hadronization

Baryons, jet fragmentation and recombination Where to go from here?

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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

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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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PHENIX at RHIC

2 Central spectrometers

2 Forward spectrometers

3 Global detectors

6

methods

Tracking: drift chamber + pad chambers outside field Hadron PID: High res. TOF ( ~ 80 ps) sector

identify higher pT pions via 0 , RICH for charged Photons: high granularity and resolution EMCAL Leptons

Electrons in central arm: tracking + RICH, EMCALMuons forward/backward: magnet pole face absorbs

hadrons, 3 tracking stations inside muon magnet + additional absorber with sampling inside

Centrality: ZDC + BBC to avoid autocorrelations Reaction Plane: BBC to avoid autocorrelations

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PHENIX looks for J/ e+e- and

Need e/ separation 1/10,000

Ring Imaging Cherenkovcounter to tag electrons“RICH detector”

For e: vpart. > cmedium

All tracks: 0.8>p>0.9 GeV/c

enriched sample (w/ RICH cut)

p

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Philosophy

Optimize for rare probesParticle ID to high pT

High resolution for high pT performancetradeoff: above is expensive, pay for by losing acceptance

Triggering and DAQ capabilityTrigger various channels besides min bias

high pT photons: calorimeter showersmuons: MuID hits; select singles or muon pairselectrons: RICH hits + overlapping energy in EMCALselect thresholds for sufficient rejection in AuAu, pp, etc.

DAQ: 100 MB/sec gives bandwidth for ALL AuAu untilsecond half of run 4 (limited acceptance = smaller events)

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What energy density is achieved?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)Using 0 = 1 fm/c

well above predicted transition!

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Initial Energy density

dET/dy() > dET/dyfinal = 1.25 x dET/dfinal = 760 GeV

Three values of 0

min = 2R/fm/c (RHIC)fm/c (SPS)

fm/c (AGS) form=ħ/<mT (form) >

≤ ħ/<mT>final = 0.35 fm/c

<mT>=(dET/d)/(dN/d)=0.57 GeV)

therm ≤ 1 fm/c (hydro-models)≤ 2 fm/c (upper limit)

Conservative lower limits on at formation and thermalization(form) > 15 GeV/fm3 ( = 0.35 fm/c)(therm) > 2.8 GeV/fm3 ( = 2.0 fm/c)

These values >> ~1 GeV/fm3 from lattice QCDQuestion: what could it be if not QGP??

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Thermalization? particle ratios and spectra

consistent with strongly expanding thermalized source

observed strangeness production complete chemical equilibrium

/K/p measurement in aBroad pt range

Statistical fit:Tch~ 160MeV, s~1.0Strangeness saturation at RHIC?

stronger radial flow at RHIC?

Exp

ansi

on v

eloc

ity

Tkin ~ 100 MeV<T> ~ 0.5

Chemical freezeout

Thermal freezeout

RHIC

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rapid thermalization? elliptic Flow

v2 scaling with eccentricity collectivity built up at early stage

hydro-models with hadronic + QGP phases reproduce (qualitatively) measured v2(pT) of pions, kaons, and protons.

v2/ecc vs centrality v2 of /K/p and hydro

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Is thermalization achieved?v2 & spectra vs. hydrodynamic models

proton pion

Hydro models:Teaney(w/ & w/oRQMD)

Hirano(3d)

Kolb

Huovinen(w/& w/oQGP)

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HBT vs. hydro models

Nobody gets HBT right!

Origin of the “HBT puzzle”

Generic explanation: Nobody does freezeout of final state right

Another explanation:Maybe we’re fooled by the extraction of the radius parameters somehow

NB: Rside source transverse radius!

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Thermalization? Hydro-models score board

hadronic + QGP hydro reproduces features of v2(pT) of , K, p require early thermalization (therm<1fm/c) + high init > 10 GeV/fm3

most fail to get v2 and spectra simultaneously unequivocal statement on presence of QGP not yet possible HBT source parameters not reproduced by hydro inconsistencies prevent firm conclusions (boo)

Source average

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Collision energy dependence

Large dET/d, dNch/d, strangeness enhancement, strong radial flow, and elliptic flow have been observed in heavy ion collision at lower energy.

smooth changes as a function of s1/2 from AGS to SPS to RHIC energies. No sudden change with collision energy has been observed.

(dNch/d)/(0.5Npart) vs s1/2Elliptic flow dv2/dpT vs s1/2

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charm yield and direct photons

experimental verification of

binary scaling of point-like

pQCD processes.

Ncoll Scaling of point-like probes

0.906 < < 1.042

dN/dy = A (Ncoll)

Charm yield scales with Ncoll Direct photon scales with Ncoll

Electron from charm decay in Au+Au @200 GeV Direct from Au+Au @200GeV

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Direct Evidence of High (parton) Density MatterHigh pT suppression

The strong suppression of high pT production is a unique phenomenon that has not been previously observed.

Deuteron-Gold measurements demonstrate that any initial-state modification of parton distributions causes little or no suppression.

Direct evidence that Au+Au collisions at RHIC have produced matter at extreme density

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Cronin effect from 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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pp

AuAubinaryAuAuAA Yield

NYieldR

/

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

PRL91, 072301(2003)

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Evidence of jet origin of high pT particles

xT = 2pT /s related to pT of scattered parton; F is xT dependent

scaling in Au+Au dominant role of hard scattering and subsequent jet fragmentation in the production of high pT hadrons.

High pT two particle correlation xT scaling of 0 and charged

0 (h+ + h-)/2

scales

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Parton energy loss

GLV: initial gluon density dng/dy~1000 & init~15 GeV/fm3

consistent with init from our dET/d, hydro models

RAA data vs GLV model

Medium induced energy loss:only currently known physical mechanism to consistently explain the high pT suppression.

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Empirical energy loss from dataF

ract

iona

l ene

rgy

loss

For power-law spectrum with A/pT

n

(we find n= 8.1 in pp)

Final spectrum = initial - <fractional shift>

<shift> due to eloss of parent partonParent pT would be:pT’ = (1+S) pT(pp)

Fractional energy loss:Sloss = 1 - 1/(1+S)

10 GeV: E/x ~ 0.5 GeV/fm

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Anomalous p/ ratio

(anti)baryon to pion excess: most striking experimental surprise at RHIC new mechanism other than universal parton fragmentation is the

dominant source of baryons in the intermediate pT range.

Large p/ ratio in 2-4 GeV/cProton scales with NcollMesons don’t

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Is Recombination the answer?

Recombination models: natural explanation for baryon/meson & apparent quark number scaling of v2

Recomb. Models explain large p/ They also predict v2/n scaling

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But baryons show jet-like properties too…

Baryons at 2-4 GeV/c pT scale with Ncoll !

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Jets in PHENIX

Large multiplicity of charged particles--solution: find jets in a statistical manner using angular correlations of particles

mixed events give combinatorial background 2 x 90 degree acceptance in phi and ||<0.35

--solution: correct for azimuthal acceptance,

but not for acceptance Elliptic flow correlations

--solutions: use published strength values and subtract (or integrate over 90° then all even harmonics are zero)

PHENIX PRL 91 (2003) 182301

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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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PHENIX 2 particle correlations

Select particles with pT= 2.5-4.0GeV/c

Identify them as mesons or baryons viaTime-of-flight

Find second particle with pT = 1.7-2.5GeV/c

Plot distribution of the pair opening angles

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Subtract the underlying event

CARTOON

flow

flow+jet dN

Ntrig d

includes ALL triggers(even those with no

associated particles inthe event)

jetUnderlying event isbig! Collective flow causes another correlation in them:

B(1+2v2(pTtrig)v2(pT

assoc)cos(2))

associated particles with non-flow angular

correlations -> jets!Treat as 2 Gaussians

1

combinatorial background in Au+Au Measure by mixed events & subtract

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Is recombination the answer?

correlations of particles with leading baryons rule out the simplest recombination models, which assume a perfectly thermal source of partons.

At present, no complete understanding of hadron formation

Jet correlation with leading proton, meson

pT trig:2.5-4 GeV/c

Count partners1.7–2.5 GeV/c

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Answer to Q0

Q0: Does central Au+Au collisions produce a state of matter? Answer: Yes.

Evidence 1: Jet suppression in Au+Au collisionSuppression of high pT particles in Au+Au

Jet origin of high pT particles demonstrated by two particle correlation and xT scaling

Absence of suppression in d+Au TAB scaling of direct photon and charm yield in Au+Au

These observations provide a direct evidence that a dense matter formed in the final state is the cause of the suppression.

Evidence 2: Strong elliptic flowScaling of v2 with eccentricity shows that a high degree of collectivity

built up at a very early stage of collisionSuccess of hydrodynamic models in reproducing the elliptic flow

shows that the state can be well described as fluid – a matter.

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Answer to Q1

Q1: If the answer is yes, is it conceivable that the state of matter consisted only of hadrons?

Answer: NoThe lower limit of the energy densities derived from

dET/d are: ≥ 15 GeV/fm3 at formation at ≤ 0.35 fm/c ≥ 2.8 GeV/fm3 at thermalisation at ≤ 2 fm/c

The hydro-models require early thermalization (therm<1fm/c) and high initial energy density > 10 GeV/fm3

Initial gluon density dng/dy~1000 and initial energy density ~15 GeV/fm3 are obtained from GLV model of jet quenching. A similarly high initial energy density is obtained by other models.

All these estimates of energy density are well in excess of ~1 GeV/fm3 obtained in lattice QCD as the energy density needed to form a deconfined phase.

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Answer to Q2

Q2: If the answer is no, is the state of matter QGP? Answer: We don’t know.

+ We know that the matter is extremely dense and it thermalize very rapidly. The estimated energy densities are all well in excess of the density needed for a QGP.

ButThere is no direct evidence that

the matter is deconfinedthe primary degree of freedom of the matter is quark and

gluonsthe matter is at high temperature (T > 170 MeV)

We currently do not have a consistent model of Au+Au collision that can describe spectra, v2, and HBT. This prevents us from drawing quantitative conclusions on the properties of the matter such as the equation of state and the presence of a mixed phase.

furthermoreThere is no obvious and common definition of QGP.

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Answer to Q3

Q3: What key questions remains to be answered? Answer:

The term “QGP” should be better definedKey predictions that derive from the properties of above defined QGP

should be given, and these predictions should be tested by RUN4 data. For example:

RAA at very high pT (Test of jet quenching models) + jet coincidence (Test of jet quenching models)Fate of J/Test of deconfinement/recombination)Charm energy loss(Test of energy loss models)Thermal radiation (Measurement of the temperature)

A consistent model of heavy ion reactions should be constructed so that we can relate the experimental observables to the property of matter in a quantitative and consistent way.

The theory community should work towards– Increased cross comparison of both definitions and model

results– More rigorous bounds on values of extracted parameters (,

EOS, etc)

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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

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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

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

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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?

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pp

AuAubinaryAuAuAA Yield

NYieldR

/

2/pp

AuAupartAuAupartAA Yield

NYieldR

/

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

PRL91, 072301(2003)

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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

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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

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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.

46

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

47

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

51

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

52

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.

53

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

54

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.

56

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

57

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

58

PHENIX PRELIMINARY

PHENIX PRELIMINARYPHENIX PRELIMINARY

PHENIX PRELIMINARY

d+Au data vs centrality

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

59

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

No large suppression as for light quarks!

PHENIX PRELIMINARY

60

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

61

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

62

Analysis

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

Asymmetry cut < 0.5

63

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

64

Nuclear Modification Factor for (compared to 0)

peripheralbinaryperipheral

centralbinarycentral

NYield

NYield

//

0

RC

P =

PHENIX Preliminary

65

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

66

Identified Associated Particles--AuAu

Trigger (not identified)

“near side” < 90° jet partner identified

“away side” > 90° opposing jet fragment identified

67

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

68

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!

69

J/ in pp and d+Au

● Total cross section :

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

70

dAu/pp versus rapidity

71

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

72

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

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

73

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

74

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

75

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!

76

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

77

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

78

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

79

Centrality selection

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

80

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)

81

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

82

Phenix-Star comparison

STAR

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

83

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%

84

Grows with s as expected

85

charm by single e production

Cross section fits into expected energy dependence

130 GeV/A Au+Au

Phys.Rev.Lett. 88 (2002) 192303