j/ production in cu+cu and au+au collisions at √s nn = 200 gev measured by phenix at rhic

J/ production in Cu+Cu and Au+Au collisions at √sNN = 200 GeV measured by PHENIX at RHIC

Andry Rakotozafindrabe

LLR – École Polytechnique

42nd Rencontres de Moriond QCD session – Italy (March 2007)

23/03/200723/03/2007

Andry Rakotozafindrabe Andry Rakotozafindrabe – LLR– LLR 22

Physics motivation – the starting point What are the properties of the hot and dense matter produced

in relativistic heavy ion collisions ?

c and b are produced in the initial parton collisions, so they can be used to probe the created medium : open charm (or beauty) energy loss energy density

Topic already covered this morning by Alan Dion

, (quarkonia) suppressed by color screening deconfinement At lower energy, NA50 (CERN) experiment measured an anomalous J/

suppression in Pb+Pb collisions, in excess of the normal suppression expected from the nuclear absorption. NA50 Collaboration, Eur. Phys. J. C39 (2005) 335

At lower energy, NA60 (CERN) recent results in In+In

At RHIC energy ? 10x √sNN 2-3x gluon density

cc bb

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Satz, J.Phys.G32:R25,2006

Screening the J/ in a QGP Sequential dissociation as the

temperature (or energy density) increases :

Energy density (τ0 = 1fm) vs the max. √s for SPS, RHIC and LHC

’ J/χc

Production ~ ~ 60% direct production J/ ~ 30% via ~ 30% via χχcc J/ J/ + x + x ~ 10% via ~ 10% via ’’ J/ J/ + x + x

Temperature of dissociation Td for for χχcc and and ’: ’: TTdd ~ 1.1 ~ 1.1 TTcc

for for J/ : Td ~ 1.5 to 2 Tc

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Physics motivation – a few complications

Sensitive to: Initial state

Modification of the parton distribution functions (shadowing, CGC)

pT broadening (Cronin effect)

Parton energy loss in the initial state ?

Final state “Normal” nuclear absorption Absorption by (hadronic ?) comovers ? Color screening ? In-medium formation (recombination) ? Flow ?

J/or

+ feed-down b, ’, c J/ + x

quarkonia production g+g fusion dominant at RHIC

energies

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J/ in PHENIX : capsule historyRun Species √s [GeV ] Ldt # J/ # J/ Reference

|y|<0.35 1.2<|y|<2.2

01 Au+Au 130 1 b-1

02 Au+Au 200 24 b-1 13 PRC69, 014901 (2004) p+p 200 0.15 pb-1 46 65 PRL92, 051802 (2004)

03 d+Au 200 2.74 nb-1 364 1186 PRL96, 012304 (2006)p+p 200 0.35 pb-1 130 448

04 Au+Au 200 241 b-1 1000 4449 nucl-ex/0611020Au+Au 62 9 b-1

05 Cu+Cu 200 3 nb-1 2300 9000 coming soonCu+Cu 62 0.19 nb-1 146Cu+Cu 22.5 2.7 b-1

p+p 200 3.8 pb-1 1500 8005 hep-ex/061102006 p+p 200 10.7 pb-1

p+p 62 0.1 pb-1

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PHENIX detector

J/J/µµ++µµ––

1.2< |y| < 2.21.2< |y| < 2.2Pµ > 2 GeV/c = 2• Tracking, momentum measurement with cathode strip chambers• µ ID with penetration depth / momentum match

J/J/ e e++ee–– |y| < 0.35|y| < 0.35 Pe > 0.2 GeV/c =

• Tracking, momentum measurement with drift chambers, pixel pad chambers• e ID with EmCAL + RICH

Centrality measurement, vertex positionCentrality measurement, vertex position Beam-beam counters (charged particle production) Zero-degree calorimeters (spectator neutrons)

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Production baseline : (Run5) p+pJ/ @ √s = 200 GeV

Total cross section in p+p

Bll.pp(J/ ) = 178 ± 3(stat) ± 53(sys) ± 18(norm) nb

in agreement with COM

hep-

ex/0

6110

20

Cross section vs rapidity better constraints on

available J/ production mechanisms

Cross section vs pTForward rapidity

<pT2> = 3.59 ± 0.06 ± 0.16

Central rapidity

energy rapidityCross section vs : pT

ppColl

ABAB yieldN

yieldR

p+pJ/ measurement used as a reference for A+BJ/ :

30.020.0

2 18.014.4 Tp

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Heavy ion results @ √s = 200 GeV Au+Au final results : nucl-ex/0611020 Cu+Cu preliminary results (QM05) but forthcoming final results (article in preparation) with

increased statistics in the dielectron channel (a factor ~2)increased statistics in the dielectron channel (a factor ~2) significant improvement of systematic errorssignificant improvement of systematic errors better precision measurement than the present Au+Au results for better precision measurement than the present Au+Au results for

NNpartpart<~100<~100

1

RAA

0

Bar: uncorrelated errorBracket : correlated error

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RHIC : beyond cold nuclear matter effects Available d+Au data

qCNM : Weak shadowing and weak Weak shadowing and weak

nuclear absorption (nuclear absorption (σabs ~ 1mb favored) derived from ) derived from model Vogt PRC71, 054902 model Vogt PRC71, 054902 (2005)(2005)

Au+Au data : even compared to the « worst » σabs~ 2mb case shown here

suppression beyond cold effects for NNpartpart>100 at >100 at y~1.7

NNpartpart>200 at >200 at y~0

Need to improve the knowledge of CNM effects at RHIC

RHIC CNM effects :σ abs = 0, 1, 2 mb @ y=0, y=2 Cold nuclear matter predictions from Vogt, nucl-th/0507027 (shadowing + σabs)


nucl-ex/0611020

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RHIC : different amount of suppression at different rapidities

RAA vs Npart :

Stronger suppression at forward rapidity than at central rapidity

Ratio forward/central ~0.6 for Npart>100

CGC (initial state effect) ?

models predicts less heavy quark production at forward rapidity than at mid rapidity K. L. Tuchin J.Phys. G30 K. L. Tuchin J.Phys. G30

(2004) S1167 (2004) S1167

ratio RAA (1.2<|y|<2.2)

/RAA (|y|<0.35)

1RAA

0

1

0


nucl-ex/0611020

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RHIC vs SPS SPS @ 0<y<1 :

√√s ~ 17 GeVs ~ 17 GeV CNM = CNM = normal nuclear

absorption σabs = 4.18 ± 0.35 mb Maximum Maximum εε ~ 3 GeV/fm ~ 3 GeV/fm3 3 ((ττ00 = 1) = 1)

Compare to RHIC @ |y|<0.35 : x10 x10 √s √s CNM = CNM = shadowing + nuclear

absorption σabs from 0 to 2mb from 0 to 2mb (Vogt, nucl-th/0507027)(Vogt, nucl-th/0507027)

Maximum Maximum εε ~ 5 GeV/fm ~ 5 GeV/fm33 ( (ττ00 = 1), = 1), higher than at SPShigher than at SPS

Same pattern of J/ suppression for the same rapidity!

Suppression beyond CNM larger at RHIC

NA50 at SPS (0<y<1)PHENIX at RHIC (|y|<0.35)PHENIX at RHIC (1.2<|y|<2.2)

Bar: uncorrelated errorBracket : correlated errorGlobal error = 12% is not shown

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RHIC vs SPS (II) : extrapolating suppression models

Suppression models in agreement with NA50 data extrapolated at RHIC energies Opposite suppression behaviour vs rapidity Unmatched suppression pattern at central rapidity

Recombination at work at RHIC ?

Dissociation by comovers (Capella et al., hep-ph/0610313)

Dissociation by thermal gluons(R. Rapp et al., nucl-th/0608033

Nu Xu et al., Phys.Rev.Lett. 97 (2006) 232301)

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Recombination at RHIC ? Suppression+recombination predictions compared to data

RRAAAA vs N vs Npartpart

R. Rapp et al. PRL 92, 212301 (2004)Thews Eur. Phys. J C43, 97 (2005)Nu Xu et al. Phys.Rev.Lett. 97 (2006) 232301Bratkovskaya et al. PRC 69, 054903 (2004)A. Andronic et al. nucl-th/0611023

Better matching with the data

but regeneration goes as the (single) charm density which

is poorly known at RHIC

What about the other variables ?

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Yield vs rapidityYield vs rapidity

RMS 1.43±0.04RMS 1.40±0.04

RMS 1.32±0.06 RMS 1.30±0.05

No recombinationAll recombination

Thews & Mangano, PRC73 (2006) 014904c

Recombination predicts a narrower rapidity distribution

with an increasing Npart

Data shows a slight decrease of the RMS with increasing

centralitynucl-ex/0611020

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Yield vs rapidityYield vs rapidity <p<pTT

22> vs N> vs Ncollcoll

Recombination predicts a narrower pT distribution

with an increasing centrality, thus leading to

a lower <pT²>

Data shows a rather flat dependence of <pT²> with

centrality

Thews, Eur.Phys.J. C43 (2005) 97, Phys.Rev. C73 (2006) 014904(and private communication).

No recombination

With recombination

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Ending where it began: revisiting the sequential dissociation (I)

Karsch, Kharzeev & Satz, PLB 637 (2006) 75 : Sequential melting overall J/ survival probability (measured/expected):

S = 0.6 S direct J/ + 0.4 S J/←’, χc

Recent lattice QCD results : direct J/ melting at 10-30 GeV/fm3

S ~ 0.6 at RHIC

RAA/CNM vs.

Bjorken energy density

00

1

y

TBj dy

dE

A

Sequential dissociation of ψ’ and χc only does not seem to be consistent with the data

dET/dy : PHENIX, PRC 71, 034908 (2005)

Bar: uncorrelated errorBracket : correlated errorPHENIX Global error = 12% + 7%Box : uncertainty from CNM effects

εBj.τ0

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Refinement :3D hydro + sequential dissociation (II)

Gunji et al., hep-ph/0703061 :

Charmonia initial spatial distribution = from collisions in the Glauber model initial spatial distribution = from collisions in the Glauber model + free streaming in a full (3D+1) hydro+ free streaming in a full (3D+1) hydro J/ survival probability ( RAA/CNM with CNM = shadowing + nuclear

absorption σabs = 1mb )

S = (1 – fFD) S direct J/ + fFD S J/←’, χc

3 free parameters : feed-down : feed-down fFD , melting temperatures , melting temperatures TJ/ and and T’,χc

+ (3D+1) hydro : same setup as the one used to reproduce charged dN/dη measured at RHIC Assuming thermalization for Assuming thermalization for ττ°≥≥°0.60.6°fm, initial energy density distribution fm, initial energy density distribution

in the transverse plane, EOS of the medium (T<Tin the transverse plane, EOS of the medium (T<Tcc and T>T and T>Tcc), … ), …

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Refinement :3D hydro + sequential dissociation (II)

Gunji et al., hep-ph/0703061 :

Charmonia J/ survival probability ( RAA/CNM with CNM = shadowing + nuclear

absorption σabs = 1mb )

S = (1 – fFD) S direct J/ + fFD S J/←’, χc

3 free parameters : Feed-down : Feed-down fFD , melting temperatures , melting temperatures TJ/ and and T’,χc

+ (3D+1) hydro

best fit with : TJ/ = 2.12 Tc

T’,χc = 1.34 Tc

fFD = 0.25

± 0.10 due to uncertainty

on σabs (1 ± 1mb)Better matching with

the data

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Summary (I) PHENIX final results on J/dileptons at forward and mid-

rapidity in p+p, Au+Au, and preliminary results in Cu+Cu :

Improved baseline Run 5 p+p with x10 more statistics than Run 3Run 5 p+p with x10 more statistics than Run 3

Suppression pattern Beyond cold nuclear effects for NBeyond cold nuclear effects for Npartpart > 200 > 200 More suppression at forward than at central rapidity More suppression at forward than at central rapidity

RatioRatio forward/central ~0.6 for N~0.6 for Npartpart>100>100 May be accounted for by CGC models May be accounted for by CGC models Suppression models (comover) predicts the opposite behaviourSuppression models (comover) predicts the opposite behaviour

Similar to SPS suppression in the same rapidity region? despite a higher Similar to SPS suppression in the same rapidity region? despite a higher energy density reachedenergy density reached

Understandable as recombinations that partially compensate the J/ suppression ? Still open question (test vs <pStill open question (test vs <pTT²> dependance and rapidity distribution)²> dependance and rapidity distribution)

cc

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Summary (II) Alternate explanations ?

Sequential dissociation with feed-down assumed to be Sequential dissociation with feed-down assumed to be ~40% and direct and direct J/J/ not melting at present energy densities is not consistent with data not melting at present energy densities is not consistent with data

(3D+1) hydro + sequential dissociation in agreement with mid-rapidity (3D+1) hydro + sequential dissociation in agreement with mid-rapidity data if direct J/data if direct J/ is melting (at is melting (at T = 2.12 Tc) and if feed-down is assumed ) and if feed-down is assumed

to be to be (25 ± 10)% Feed-down not measured at RHIC energies At lower energies, large deviations between experiments

Need to improve knowledge on cold nuclear effects at RHIC Stay tuned : forthcoming final results for Cu+Cu !

Improved precision for the measurements in the range Npart <~ 100Improved precision for the measurements in the range Npart <~ 100

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Back-up

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Hint of things to come Final results for Cu+Cu

What about the forward vs central suppression at lower Npart ?

… Improved reference p+p :

x3 higher statistics from run 6x3 higher statistics from run 6 Future measurements in ’ ? Future measurements in χc Planning Au+Au (1 nb-1 vs 0.24

nb-1 in run 4 ) with high luminosity during Run 7

Later runs : d+Au with higher luminosity (28 nb-1 vs 2.7 nb-1 in run 3) ?

Run 6 200GeV p+p

Invariant Mass (GeV/c2)

A. Bickley, Hard Probes 06

(c - J/) Mass (GeV/c2)

PHENIXRun 5 200GeV p+p

(c - J/) Mass (GeV/c2)

Wor

k un

der

prog

ress

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Upsilon measurement

PHENIX : 1st Upsilons at RHIC from ~3pb-1 collected during the 2005 p+p run.

Dimuon mass spectrum for the two muon arms added

together.

PHENIX QM05

y~1.7~10 counts

STAR QM06

STAR Preliminary p+p 200 GeV e+e- Minv

Background Subtracted

19dt pb L

y=0~50 cnts

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STAR results and near future

STAR – J/ Run5 ppSTAR – J/ Run4 AuAu

STAR Preliminary

Dataset Au+Au@200 GeV : No trigger due to high backgroundNo trigger due to high background Just a faint signalJust a faint signal For efficient J/For efficient J/ trigger, full barrel ToF is trigger, full barrel ToF is

needed (just patch in Run5)needed (just patch in Run5) p+p@200GeV (Run5):

trigger commissioning (~1.7M events)trigger commissioning (~1.7M events) Run 6: expect 500-1000 (work in progress)

M. Cosentino, QWG06

Upsilon

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J/ production Production

~ ~ 60% direct production J/ ~ 30% via ~ 30% via χχcc J/ J/ + x + x ~ 10% via ~ 10% via ’’ J/ J/ + x + x

Large deviations between experiments : χc feed-down fraction vs √s Not measured at RHIC energiesNot measured at RHIC energies

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Invariant yield vs tranverse momentum

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<pT2> vs Npart

A closer look at <pT2> vs Npart

hep-ex/0611020 nucl-ex/0611020

hep-ex/0611020 nucl-ex/0611020

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Available d+Au data CNM : Weak shadowing (modification of gluon Weak shadowing (modification of gluon

distribution) and weak nuclear absorption distribution) and weak nuclear absorption ((σabs ~ 1mb favored) derived from model ) derived from model Vogt PRC71, 054902 (2005)Vogt PRC71, 054902 (2005)

Data driven parametrizations of CNMData driven parametrizations of CNM Karsch, Kharzeev & Satz, PLB 637

(2006) 75 Granier de Cassagnac, hep-ph/0701222

gluons in Pb / gluons in p

x

Shadowing AntiShadowing

Nucl. Phys. A696 (2001) 729-746

Cold nuclear effects : d+AuJ/

Vogt, PRC71, 054902 (2005), Kopeliovich, NP A696, 669 (2001)

Phys. Rev. Lett. 96 (2006), 012304

Low x2 ~ 0.003(shadowing region)

y ~ 0 : intermediate xAu ~ 0.020

xd xAu

J/ Northy > 0

y > 1.2 : low xAu ~ 0.003

xdxAu

J/ Southy < 0

rapidity y

y < -1.2 : large xAu ~ 0.090

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RHIC : beyond cold nuclear effects (II) ? Comparison to a data driven parametrization of CNM (Granier de

Cassagnac, hep-ph/0701222) in the same centrality classes CNM : RCNM : RAAAA(y, b) = (y, b) = ΣΣcollisionscollisions[[RRdAdA(-y,b(-y,b11

ii).R).RdAdA(+y,b(+y,b22ii)]/Ncoll )]/Ncoll

Essentially the same conclusions as the previous slide But stat+syst error that comes from d+Au data are visible Need a higher luminosity d+Au sample

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Small centrality dependence Model with absorption +

shadowing ( black lines* ): shadowing EKS98shadowing EKS98 σσabsabs = 0 to 3 mb = 0 to 3 mb

σabs = 1 mb good agreement

σabs = 3 mb is an upper limit

weak shadowing and weak nuclear absorption

J/ production in d+Au vs centrality

High x2 ~ 0.09

Low x2 ~ 0.003*Colored lines: FGS shadowing for 3 mb

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SPS vs RHIC (III) : RAA/CNM vs Npart

SPS @ 0<y<1 : CNM = CNM = normal nuclear absorption

σabs = 4.18 ± 0.35 mb

Compare to RHIC @ |y|<0.35 : CNM = CNM = shadowing + nuclear

absorption σabs=1 mb (Vogt, nucl- (Vogt, nucl-

th/0507027)th/0507027)

Additionnal syst. error from uncertainity on CNM Need to improve knowledge on Need to improve knowledge on

cold nuclear effects at RHICcold nuclear effects at RHIC

Suppression beyond CNM larger at RHIC

Bar: uncorrelated errorBracket : correlated errorGlobal errors (12% and 7%) are not shown here.Box : uncertainty from CNM effect

NA50 at SPS (0<y<1)PHENIX at RHIC (|y|<0.35)PHENIX at RHIC (1.2<|y|<2.2)

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Recombination at RHIC ?

R. Vogt nucl-th/0507027 (EKS)

R. L. Thews, M. L. Mangano Phys.Rev. C73 (2006) 014904

0mb

3mb

100% Recombination(shape only)

RAA vs y

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Charm flow

Significant flow observed for heavy flavor electrons Main source is Main source is DD meson meson

(1) Consistent with c-quark thermalization (2) large cross section is needed in AMPT ~10 mb (3) Resonance state of D & B in sQGP Charm quark strongly coupled to the matter

S. Sakai QM06 M. Djordjevic et al., Phys.Lett.B632 (2006) 81

c and b quark pT distributions at mid-rapidity before fragmentation : b contribution is

dominant at high pT

dNg/dy=1000

[PRC72,024906]

[PRC73,034913]

[Phys.Lett. B595 202-208 ]

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Computing the J/ yield

: number of ‘s reconstructed

: probability for a thrown and embeded

into real data to be found

(considering reconstruction and trigger efficiency)

: total number of events

: BBC trigger efficiency for events with a

: BBC trigger efficiency for minimum bias events

Invariant yield :

For Au+Au or Cu+Cu collision : ~

i : i-th bin (centrality for e.g.)

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Collision geometry and centrality (eg : Cu+Cu)

For a given b, Glauber model (Woods-Saxon function) predicts:● Npart (No. participants)● Ncoll (No. binary collisions)

10 fm b 0 fm0 Npart 1040 Ncoll 198

Spectators(neutrons) EZDC

Participants(charged particles)

QBBC

BBC charge N+S distribution for min.bias Cu+Cu √s = 200 GeV data

80-88%70-80%

etc

Monte-Carlo Glauber model

Probability for a given Npart

Each participant contributes to a Negative Binomial distribution of hits

Fit BBC charge distribution

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Energy density Longitudinally expanding plasma :

dEdETT/d/dηη measurement at mid-rapidity by PHENIX EMCal measurement at mid-rapidity by PHENIX EMCal

Which Which ττ00 ? ?

20

1

Rdy

dETBj

R2

0 ~ 1 fm/c

cross

~ 0.13 fm/c

secondaries formation

~ 0.35 fm/c

therm

~ 0.6 - 1 fm/c

j/ production in cu+cu and au+au collisions at √s nn = 200 gev measured by phenix at rhic

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