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Heavy Quarks and Heavy Quarkonia

at RHIC

April 7th 2006DongJo Kim

Department of Physics University of Jyvaskyla, Finland

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1. A short Overview of RHIC results.① RHIC history② Jet-Quenching (pion RAA, Jet suppression)③ Flow ( light hadrons, even heavier particles)

2. Extension from Light quarks to heavy quarks 3. How to measure Heavy flavor ?

① Semi-leptonic heavy flavor decay (Cocktail/Converter)② J/Ψ

4. PHENIX heavy flavour measurement① Open charm Results( RAA , charm flow )

Radiative energy loss, bottom contribution② J/psi Results ( RAA )

Suppression (Screening) vs Enhancement (recombination)

5. Summary

Outline of TalkOutline of Talk 1-(2)1-(2)1-(2)1-(2)

1-(2)1-(2)1-(2)1-(2)

4-(1)4-(1)4-(1)4-(1)

4-(1)4-(1)4-(1)4-(1)

4-(2)4-(2)4-(2)4-(2)

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RHIC program is operating very successfully.PHENIX online data transfer and reconstruction remarkable

RHIC HistoryRHIC History

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Suppression is very strong (RAA=0.2!) and flat up to 20 GeV/c

Energy loss of partons in dense matter A medium effect predicted in QCD( Energy loss by colored parton in medium composed of unscreened color charges by gluon bremsstrahlung : LPM radiation )Gyulassy, Wang, Vitev, Baier, Wiedemann… See nucl-th/0302077 for a review. Baier, Dokshitzer, Mueller, Peigne, Shiff, NPB483, 291(1997), PLB345, 277(1995), Baier hep-ph/0209038

The matter is extremely opaqueThe matter is extremely opaque

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Collective FlowCollective Flow

Identified charged hadron v2 indicates① Early thermalization② Constituent quark scaling Partonic collectivityEven Φ flows, within the errors consistent with other hadrons

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• PHENIX– Single electron measurements in

p+p, d+Au, Au+Au sNN = 130,200,62.4 GeV

• STAR– Direct D mesons hadronic

decay channels in d+Au• D0Kπ• D±Kππ• D*±D0 π

– Single electron measurements in p+p, d+AuPhys. Rev. Lett. 88, 192303 (2002)

Experimentally observe the decay products of Heavy Flavor particles (e.g. D-mesons) (* DongJo )

– Hadronic decay channels DKD00

– Semi-leptonic decays De() Ke

Meson D±,D0

Mass 1869(1865) GeV

BR D0 --> K+- (3.85 ± 0.10) %

BR D --> e+ +X 17.2(6.7) %

BR D --> ++X 6.6 %

How to measure Heavy Flavor ?How to measure Heavy Flavor ?

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S/B > 1 for pT > 1 GeV/c

Run04: X=0.4%, Radiation length

Run02: X=1.3%

Signal/Background

We use two different methods to determine the non-photonic electron contribution (Inclusive = photonic + non-photonic )

• Cocktail subtraction – calculation of “photonic” electron background from all known sources• Converter subtraction– extraction of “photonic” electron background by special run with additional converter (X = 1.7%)

New Electron ResultsNew Electron Results

Ch

arm

/B

otto

m

ele

ctro

ns

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Proton-Proton Baseline Gold-Gold Suppression

Non-Photonic Electron SpectraNon-Photonic Electron Spectra

Clear high pT suppression developing towards central

collisions

Clear high pT suppression developing towards central

collisions

Fixed Order Next-to-Leading Log pQCD calculation(M. Cacciari, P. Nason, R. Vogt hep-ph/0502203 )

Fixed Order Next-to-Leading Log pQCD calculation(M. Cacciari, P. Nason, R. Vogt hep-ph/0502203 )

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Suppression of High pT CharmSuppression of High pT Charm

pp

AA

AAAA

dpd

T

dpNd

R

3

3

3

3

Strong modification of

the spectral shape in

Au+Au central collisions

is observed at

high pT

Theory Comparison

Disagreement with PHENIX preliminary data!

1000gdN

dy

dNg/dy=1000

M. Djordjevic, M. Gyulassy, S.Wicks, Phys. Rev. Lett. 94, 112301M. Djordjevic, M. Gyulassy, S.Wicks, Phys. Rev. Lett. 94, 112301

How can we solve the problem?

Reasonable agreement, but the dNg/dy=3500 is not physical!

3500gdN

dy

dNg/dy=3500N. Armesto et al.,

Phys. Rev. D 71, 054027 (2005)

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(3) q_hat = 14 GeV2/fm

(2) q_hat = 4 GeV2/fm

(1) q_hat = 0 GeV2/fm

(4) dNg / dy = 1000

Theory curves (1-3) from N. Armesto, et al., hep-ph/0501225(4) from M. Djordjevic, M. Gyulassy, S.Wicks, Phys. Rev. Lett. 94, 112301

Theory ComparisonTheory Comparison

Data favor models with large parton densities and strong coupling

Main uncertainty:Bottom

contribution at high pT

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• Electrons • Pionss = .3

Plot shown by Wicks/Horowitz at HF workshopIn BNL Dec 05

Plot shown by Wicks/Horowitz at HF workshopIn BNL Dec 05

+ Elastic Energy loss ?+ Elastic Energy loss ?+ Elastic Energy loss ?+ Elastic Energy loss ?First results indicate that the elastic energy loss may be important

M. G. Mustafa, Phys.Rev.C72:014905,2005First results indicate that the elastic energy loss may be important

M. G. Mustafa, Phys.Rev.C72:014905,2005

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Charm Flows Charm Flows

Charm quark exhibit a degree of thermalization

~ comparable to that of light partons

Theory curves from:Greco, Ko, Rapp: Phys. Lett. B595 (2004) 202

v2 (D) = v2 ()

v2 (D) = 0.6 v2 ()

v2 (D) = 0.3 v2 ()

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Electrons from heavy flavor decays were measured at s = 200 GeV in Au+Au collisions at RHIC

Nuclear modification factor RAA shows a strong suppression of the electrons at high pT in Au+Au collisions

Observed RAA favors models with large parton densities and strong coupling

Charm flows! v2(D) ~ 0.6 x v2(p) , indicating substantial coupling of the charm quarks to the bulk dynamics of the medium

Charming? Summary Charming? Summary

(3) q_hat = 14 GeV2/fm

(2) q_hat = 4 GeV2/fm

(1) q_hat = 0 GeV2/fm

(4) dNg / dy = 1000

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In a calculation by Teaney and Moore (hep-ph/0412346), they calculate the expected elliptic flow (v2) and transverse momentum modifications for different charm quark diffusion coefficients (free parameter). The two effects go hand in hand.

Charm suppression and FlowCharm suppression and Flow

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A .Different predictions on J/Ψ behaviour when QGP is formed

Perturbative Vacuum

cc

Color Screening

cc

① Color screening will lead to suppression of charmonium production in heavy ion collisions (T. Matsui, H. Satz, Phys. Lett. B178(1986)416).

② Lattice QCD results show that the confining potential between heavy quarks is screened at high temperature. This screening should suppress bound states such as J/Ψ. However, recent lattice results indicate that the J/Ψ spectral functions only show modest modification near the critical temperature, and thus may not be suppressed until higher T.

③ But after taken the recombination into account, much less suppression or even enhancement is predicted

A. Andronic, P.B. Munzinger et al., nucl-th/0303036 L. Grandchamp, R. Rapp, hep-ph/0103124 R.L. Thews et al., Phys. Rev. c63(2001)054905

Heavy QuarkoniaHeavy Quarkonia

B .Disentangle Normal nuclear effectsGluon shadowing, Nuclear AbsorptionInitial state energy loss , Cronin effect.

free energy : S.Digal et al. Phys.Rev.D64(2001)094015 linear comb. of both: C.Y.Wong hep-ph/0509088 internal energy: W.M.Alberico et al. hep-ph/0507084

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J/ e+e– identified in RICH and EMCal

– || < 0.35 – p > 0.2 GeV

J/μ+μ– identified in 2 fwd

spectrometers– 1.2 < || < 2.4– p > 2 GeV

Centrality and vertex given by

BBC in 3<||<3.9

How does PHENIX see the J/ ?How does PHENIX see the J/ ?(* DongJo )(* DongJo )

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Computing the J/ yieldComputing 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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–1.95 < y < –1.70

Signal extraction in Cu+CuSignal extraction in Cu+Cu

• Cuts :– Dimuons cuts

• 2.6 < mass < 3.6 GeV/c²• 1.2 < |rapidity| < 2.2

– Track quality cuts– …

• Combinatoric background from uncorrelated dimuons :– Nbgd = 2√(N++. N– –)

• Signal = number of counts within the J/ invariant mass region • (2.6 – 3.6 GeV/c²) after subtracting Nbgd to the distribution of the opposite sign dimuons.

• Systematic errors : ~10% from varying fits of the background subtracted signal. Also account for the physical background that can be included into the previous counting.

iJ

iMB

iJi

Ay

NNJCuCu

dy

dNB

.

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Background sourcesBackground sources

• Physical background: correleted dimuons

– Drell-Yan:

– Open charm: D, D µ± + …

• Combinatoric background: uncorrelated dimuons

, K µ + … (decay before the absorber)

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Getting acc*eff correction factors in Cu+CuGetting acc*eff correction factors in Cu+Cu

• Using Monte Carlo J/ generated by PYTHIA over 4π• embed the J/ within muon arm acceptance into real minimum bias Cu+Cu

data• Apply to them the same triggers and signal extraction method as the ones

applied to the data Acc.eff(i) is the probability that a J/ thrown by PYTHIA in a given bin

i to survive the whole process followed by the data

Acc*eff vs rapidity (statistical errors only)

Systematic errors :

• 5% from track/pair cuts and uncertainities in pT, y and z-vertex input distribution

• 8% from run to run variation (mainly due to the varying number of dead channels in MuTr).Acc*eff vs pT (statistical errors only)

Acc*eff vs centrality (statistical errors only)

iJ

iMB

iJi

Ay

NNJCuCu

dy

dNB

.

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σabs =1 mb

RHIC : beyond cold nuclear effects ?RHIC : beyond cold nuclear effects ?• Available d+Au data :

– Weak shadowing (modification of gluon distribution) and weak nuclear absorption (σabs

~ 1mb favored)

• Au+Au data : even compared to the « worst » σabs~ 3mb case

– Factor 2 of suppression beyond cold effects in the most central Au+Au bin

ppColl

ABAB yieldN

yieldR

RRdAdAPhys. Rev. Lett 96, 012304 (2006)

1 mb3 mb

rapidity

σabs =3 mb

SuppressionSuppressionFactor ~ 2 Factor ~ 2

Number of participants

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RHIC vs SPS (I) : raw comparisonRHIC vs SPS (I) : raw comparison

• SPS :– √s ~ 17 GeV i.e. a factor 10 below

RHIC

– Cold effect = normal nuclear absorption σabs = 4.18 ± 0.35 mb

– Maximum ε ~ 3 GeV/fm3 (τ0 = 1)

• Compare to RHIC : – Cold effect = shadowing +

nuclear absorption σabs ~ 1mb (Vogt, nucl-th/0507027)

– Maximum ε ~ 5 GeV/fm3 (τ0 = 1), higher than at SPS, but still, the same pattern of J/ suppression !

SPS normalized to NA51 p+p value (NA60 preliminary points from Arnaldi, QM05).

NA50Pb+Pb

NA60In+In

PHENIXAu+Au

PHENIXCu+Cu

PHENIX cold effectNA50 cold effect

PHENIX : |y|~1.7

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RHIC vs SPS (II) : extrapolating suppression models

RHIC vs SPS (II) : extrapolating suppression models

• Suppression models in agreement with NA50 data overestimate the suppression when extrapolated at RHIC energies :– quite striking for mid and

most central Au+Au bins– already the case for Cu+Cu

most central bins ?(Hadronic?) co-mover scattering

Direct suppression in a hot medium :Cu+Cu Au+Au

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Some recombination effects ?Some recombination effects ?

• Adding some regeneration that partially compensates the suppression : there is a better agreement between the model and the data.

Direct suppression in a hot medium :Cu+Cu Au+Au

Regeneration :Cu+Cu Au+Au

Total :Cu+Cu Au+Au

Grandchamp et al. hep-ph/0306077

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Recombination predictions for < pT² > vs NcollRecombination predictions for < pT² > vs Ncoll

• Recombination ( Thews et al., nucl-th/0505055 ) predicts a narrower pT distribution with an increasing centrality, thus leading to a lower <pT²>

• Within the large error bars :– <pT²> seems to be consistent with a flat dependence– data falls between the two hypothesis partial recombination ?

p+p, d+Au, Cu+Cu, Au+Au

No recombination

With recombination

No rec

ombin

ation

With recombination

Open markers : |y|<0.35Solid markers : |y|~1.7

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Recombination predictions vs rapidityRecombination predictions vs rapidity

• Recombination ( Thews et al., nucl-th/0505055 ) predicts a narrower rapidity distribution with an increasing Npart.

• Going from p+p to the most central Au+Au : no significant change seen in the shape of the rapidity distribution.

No recombinationAll recombination

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SummarySummary

PHENIX preliminary results on J/dileptons at forward and mid-rapidity in Cu+Cu and Au+Au :

• Suppression pattern– Beyond cold nuclear effects, at least factor 2 of suppression in most

central Au+Au events– Similar to SPS suppression, despite a higher energy density reached– Overestimated by models in agreement with NA50 data and

extrapolated at RHIC energy• Understandable as recombinations that partially

compensate the J/ suppression ?– Still open question (test vs <pT²> dependance and rapidity distribution)

• Alternate explanations ? – Direct J/ is not melting at present energy densities ? Only the higher

mass resonances ’ and χc ? (recent lattice QCD results)• Need to improve knowledge on cold nuclear effects at RHIC

cc

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SummarySummary

• A wealth of new PHENIX data on heavy quarks and heavy quarkonia.

• Charm is a very optimal probe of thermalization and properties of the medium, but the price for this may well be the loss of a probe via quarkonia for deconfinement.

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• J/Ψ Analysis Status • J/Ψ Analysis Status • 20004 Au+Au,2005 Cu+Cu( ppg member )

– Acceptance x Efficiency corrections– LVL2 efficiency – Fine Detector response tuning– V2 analysis

• 2005 , p+p( ppg member ) & run6 status– large statistics working in progress– Finalizing all necessary stuffs

• Single muon Analysis Status • Single muon Analysis Status • QM05 Results for Light Hadrons at 200GeV• Cu+Cu 62GeV by Hot Quark 2006 at Italy, May 15th – 20th

( +Prompt muons )

• Y-PHENIX Computing Farm • Y-PHENIX Computing Farm

Analysis Status Analysis Status

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Thanks !!!Thanks !!!

• New Life begins in Finland

• New Alice Analysis begins !

• New baby is coming !

• Lots of Sports activities !

• New Life begins in Finland

• New Alice Analysis begins !

• New baby is coming !

• Lots of Sports activities !

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Backup slidesBackup slides

• Charm Raa more from GLV

• PHENIX/STAR comparisons

• Cocktail Analysis

• Electron spectra in p+p collisions (FONLL)

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Why, according to pQCD, pions have to be at least two times more suppressed than single electrons?

Suppose that pions come from

light quarks only and single e-

from charm only.

Pion and single e- suppression would really be the same.

g

0

b

b+ce-

However,

1) Gluon density to pions increases the pion suppression, while

2) Bottom contribution to single e- decreases the single e- suppression

leading to at least factor of 2 difference between pion and single e- RAA.

35/33RAA(e-) / RAA(0) > 2

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Plot shown by Wicks/Horowitz

What is the difference between these plots?1. alpha_s = 0.3 (left) and alpha_s = 0.4 (right)2. The STAR data shown at QM2005 and in their proceedings are different.

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Heavy quark suppression with the elastic energy loss

The elastic energy loss significantly changes the charm and bottom suppression!

CHARM

BOTTOM

Done by Simon Wicks.

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The three types of D mesons that contribute single electrons are:

name b.f. DeX percentage contribution to electrons in PYTHIAD+ 17.2% 21.6%D0 7.7% 66.8%D+

S 8.0% 11.6%

Note that most all excited charm mesons do not decay semi-leptonically, but only contribute via sequential decayD*+ D0 + 68.3%

D+ 0 30.6%D+ 1.1%

D*0 D0 0 61.9%D0 38.1%

D+/D0 = 0.32 (PYTHIA) gives an average b.f. DeX of 9.7%PHENIX paper uses D+/D0 = 0.65 0.35 which gives b.f. DeX of 11.0%Theory prediction of Lin, Vogt, Wang uses b.f. DeX of 12.0%

Possible Ds Measurement ?Possible Ds Measurement ?

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Not All Experiments Agree EitherNot All Experiments Agree Either

RAA agrees, but the proton-proton references are different by ~ 50%.

0.2

0.4

Also, can the theory resolve an RAA suppression value of 0.2? Is the parton density then too high?

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ComparisonComparison

Not shown were "30-40%" systematic errors.

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Cocktail Subtraction Analysis

Cocktail Subtraction Analysis

• Calculate inclusive single electron spectrum from all known electron sources: 0 Dalitz decay (dominant

contributor at low pt)– Photon conversions in PHENIX

material– Other light meson’s

(’) leptonic decays– Direct radiation contribution– Weak kaon decays electrons (Ke3)

• Input to the Cocktail 0 & ± invariant pT distributions

as published by PHENIX– Yield ratios of other light mesons

to pions as measured at RHIC (where available)

– Use mT scaling of pion momentum distribution for light mesons

– Photon conversions from full simulation of PHENIX apparatus

– Direct and Ke3 from PHENIX measurements

• Excess of the data over the Cocktail prediction can be interpreted as heavy flavor particle semi-leptonic decays contribution

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Note: Bottom dominates for pT> 2.5 GeV/c

Comparison with PYTHIA (tuned to available data)pT < 1.5 GeV/c: reasonable

pT > 1.5 GeV/c: spectra

“harder” than PYTHIA LOhard fragmentation?bottom enhancement?higher order contributions?

Comparison with FONLLFixed Order Next-to-Leading Log

pQCD calculation

(M. Cacciari, P. Nason, R. Vogt

hep-ph/0502203 )better description of spectral shapestill room for further contributions

from jet fragmentation?

PHENIX data

Non-Photonic Single Electron Spectra pp @ s = 200 GeV

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Heavy quarks (charm and beauty) - produced early in the collision. Live long enough to sample the plasma Intrinsic large mass scale allows precise calculations What can we look in order to find out the characteristics or properties of the

medium(QGP)

Yields of charm and beauty pairs compared to first principle lattice simulations determine the energy density and temperature J/Ψ suppression

Comparison between light and heavy quark suppression distinguishes between theoretical models of energy loss in the QGP Charm vs Light quark energy loss ( Jet-Quenching )

Mass dependence of diffusion of heavy quarks determines plasma properties, e.g. viscosity and conductivity Charm flow

B. Muller

S. Bethke

c

b

Why Heavy Quarks ?Why Heavy Quarks ?