Recent Results from . . on Heavy Flavor and Electromagnetic Probes at RHIC

Recent Results from Recent Results from .. .. on on Heavy Flavor and Heavy Flavor and

Electromagnetic Probes Electromagnetic Probes at RHIC at RHIC Andrew Glenn

University of Coloradofor the PHENIX collaboration

March 27, 2006

March 27, 2006 Andrew Glenn

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OutlineOutline

•Electromagnetic Probes–Direct Photons–Virtual Photons

•Heavy Flavor Production–Open Charm–Hidden Charm (J/Ψ)


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Electromagnetic ProbesElectromagnetic Probes

space

time

Hard Scattering

AuAu

Exp

ansi

on

Hadronization

Freeze-out

QGPThermaliztion

e- e+

electro-magnetic radiation: , e+e-, m+m-

rare, emitted “any time”; reach detector unperturbed by strong final state interaction

γ


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Photon SourcesPhoton Sources

PRC 69(2004)014903

• Initial hard scattering (p+p) pQCD• Thermal radiation from QGP (1<pT<3GeV)• Hadron-gas interaction (pT<1GeV/c)

() (), K* K• Compton scattering in hard scattered and thermal

partons (Jet-photon conversion)• Bremsstrahlung of hard scattered partons in medium

(small compared to the above)


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NO direct photon suppression (initial state), and large 0 suppression (final state)

Direct Photon BaselineDirect Photon Baseline

S.S.Adler, et. al. (PHENIX Collaboration), PRL 94, 232301(2005)

Nuclear Modification factorAA

AAAB pp

dNR

T dσ=


6

32

222

2

2

2

2

112

14

13

21)

M

m()m(F

m)

m

m(

m

m

dm

dN

Nee

eeeeee

e

ee

e

ee

ee −+−=α

Including Virtual PhotonsIncluding Virtual Photonsphase space factor

1 for high pT g

• Ratios of Minv bins to lowest one

• If no direct photons: ratios can be calculated from Dalitz decays

• If excess: direct photons

*

*

incl

direct

incl

direct

=

Ratios


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p+p direct photon

Thermal Hint?Thermal Hint?

• For pT<3GeV/c, thermal photon contribution looks dominant

• However, recent p+p result needs to be considered– Factor of ~4 larger than NLO pQCD at 3GeV/c! (still within error, though)

• Smaller errors on real photon will help for making a conclusion.

NLO pQCD: L.E.Gordon and W. Vogelsang, PRD48(1993)3136

pQCD is LO!

€

Inclusive /π 0

γ Decay /π 0

⎛

⎝ ⎜

⎞

⎠ ⎟≈γ Decay + γ Direct

γ Decay


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High Mass Virtual PhotonsHigh Mass Virtual PhotonsDilepton continuum


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Photon HighlightsPhoton Highlights

• High pT (>6GeV/c ) photon yield is well described by NLO pQCD calculation

• Virtual photon measurement using very low mass dileptons improves error bars at low pT

• Hint of non-pQCD (thermal?) photons in central collisions


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Heavy QuarksHeavy Quarks

• Carry the information of early stage of collisions.– Charm quark is massive (even at RHIC energy).

– Creation takes place only at the beginning of collisions.

• How are heavy quarks are effected by the medium?


11Heavy flavor electrons in Heavy flavor electrons in p+pp+p


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Prompt Prompt in p+p in p+p

PHENIX Preliminary

Appears to be little rapidity dependence of heavy quark production in p+p (large errors though)


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Quark Energy LossQuark Energy Loss

•What about heavy quarks ?•2001, proposed “dead cone” effect suggests smaller energy loss of charm •Recent theories propose energy loss of charm quark is similar to light quarks.(Armesto et al, PRD 71, 054027, 2005; M. Djordjevic et al., PRL 94, 112301, 2005.)


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Heavy Flavor in Au+AuHeavy Flavor in Au+Au

preparing the high pT spectrum (up to pT = 10 GeV/c).


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(3) q_hat = 14 GeV2/fm



(4) dNg / dy = 1000

Theory curves (1-3) from N. Armesto, et al., PRD 71, 054027

(4) from M. Djordjevic, M. Gyullasy, S.Wicks, PRL 94, 112301

• We see strong suppression even for heavy quark (charm).

•The data provides a strong constraint on the energy loss models.

Heavy Flavor RHeavy Flavor RAAAA in Au+Au in Au+Au


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Open Charm Flow in Au+AuOpen Charm Flow in Au+Au

Theory:Greco, Ko, Rapp: PLB 595 (2004) 202

• Significant anisotropy is observed for heavy flavor electron.

• v2 has good agreement of charm flow assumption below pT < 2.0 GeV/c

• In high pT region (pT > 2 GeV/c), v2 is reduced. (b quark contribution?)


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Theory AsideTheory AsideIn 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. The two effects go hand in hand.

Anything that increases the cross section for interactions will have this general effect.


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Open Charm HighlightsOpen Charm Highlights• Binary scaling of total charm

yield works well.

• Nuclear modification factor RAA shows a strong suppression at high pT region.

• Non zero v2 of heavy flavor electron observed.

• HEAVY QUARKS ARE SIGNIFICANTLY AFFECTED BY THE MEDIUM


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J/J/ΨΨ Production Production

QGP Mixed phase Freeze out

• Gluon Shadowing(Modification ofPDF in nuclei)

Nuclear

• Nuclear absorptionby the spectators• Cronin effect

• Color screening (Dissociation by gluons)

Need to understand the J/Ψproduction in each collision stage.

• Formation of J/Ψ by cc coalescence • Comover scattering


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RRAAAA of J/ of J/ΨΨ in Au+Au/Cu+Cu in Au+Au/Cu+Cu

|y|<0.35 1.2<|y|<2.4

Constrained by d+Au

•Suppression increased toward the central collisions.Factor of 3 suppression at most central (Au+Au)

•Beyond the suppression from cold matter effect.

•Same pattern between Au+Au and Cu+Cu at forward-rapidity, but different pattern at mid-rapidity.


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RRAAAA and Suppression Models and Suppression Models

Co-mover (σabs = 1mb)Direct dissociation(+Comover)QGP screening

(+Comover, feed down)

J/Ψ suppression at RHIC is over-predicted by the suppression models that described SPS data successfully.


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Recombination ModelsRecombination Models

•Better matching with results compared to the suppression models.

•Don’t forget about free paramerters.

•At RHIC (energy): Recombination compensates stronger suppression?


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Invariant pInvariant pTT distributions distributions

Cu+Cu

Extraction of <pT2> by fitting with A(1+(pT/B)2)-6


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<p<pTT22> as a function of N> as a function of Ncolcol

Au+Au = RED

Cu+Cu = BLUE

Dashed: without recombination

Solid: includes recombinationRecombination model

matches better to the data...But don’t forget the error bars

nucl-th/0505055


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Connected ObservablesConnected ObservablesSuppression due to multiple scattering in cold nuclear matter

Npart

A.M. Glenn, Denes Molnar, J.L. Nagle nucl-th/0602068


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Rapidity dependenceRapidity dependence

p+p

40-93%20-40%0-20%

Cu+Cu (200GeV)

p+p60-94%

40-60%

0-20%

20-40%

AuAu

CuCu

PHENIX Preliminary PHENIX Preliminary

•No significant change in rapidity shape in Au+Au and Cu+Cu.•RAA is flat (within errors) as a function of rapidity, which is not predicted by the recombination model.

nucl-th/0505055nucl-th/0507027


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RRAAAA vs. p vs. pTT in Au+Au/Cu+Cu in Au+Au/Cu+Cu

•Suppression of J/Ψ yield at low pT in both Au+Au and Cu+Cu.•High pT J/Ψ escape the medium? Leakage effect? [Phys. Lett. B 607 (2005)]

•Might one expect “pile up” at low pT for recombination+energy loss?


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J/J/ΨΨ Highlights Highlights• Factor of 3 (4 Cu+Cu) suppression in most central collisions

• Beyond the suppression from cold matter effects.

• Over-predicted by the suppression models effective for SPS.

• Possible signs of recombination, but plenty of open questions (flies in the ointment?)


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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 Florida Technical University, Melbourne, FL Georgia State University, Atlanta, GA University of Illinois Urbana Champaign, 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

Rikkyo University, Tokyo, Japan 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; 58 Institutions; 480 Participants*

*as of January 2004


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BONUS SLIDES


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Related talks at SQMRelated talks at SQM• Elliptic flow of inclusive single muon in sqrt(s_NN)

= 200 GeV Au+Au collision at PHENIXIhnJea Choi Yonsei University

• Medium Modification of Heavy Flavor Production Measured by PHENIX in Au+Au Collisions at sqrt(s_NN)=200 GeVAlan Dion State University of New York at Stony Brook

• J/Psi measurements in Cu+Cu and Au+Au collisions at sqrt(s) = 200 GeV by PHENIX at RHICAndry Rakotozafindrabe Laboratoire Leprince Ringuet (LLR) - École Polytechnique (France)

• The Azimuthal Anisotropy of Electrons from Heavy Flavor Decays in sqrt{s_{NN}}=200 GeV Au-Au Collisions at PHENIXShingo Sakai University of Tsukuba

• Measurement of Low Mass Dielectron Continuum in sqrt(s_NN)=200GeV Au-Au Collisions in the PHENIX Experiment at RHICAlberica Toia Stony Brook UniversityMeasurement of Open

• Heavy Flavor with Single Muons in pp and dAu collisions at 200 GeVXiaorong Wang, New Mexico State University


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PHENIX experimentPHENIX experiment

Muon Arms:Muons at forward rapidity

J/ 1.2< < 2.4 P > 2 GeV/c

Central Arms:Hadrons, photons, electrons

J/ e+e- 0.35 Pe > 0.2 GeV/c (2 arms x /2)

Centrality measurement: Beam Beam Counters together with Zero degree calorimetersCentrality is mapped to N

part (N

col) using Glauber model


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• Measure inclusive electron pairs or photons• Measure 0 and spectra via 2 decay, and estimate

background electron-pairs or photon distribution– Other hadron spectra estimated by mT scaling of power-law fit

to 0– Conservative assumption on normalization: /0=0.450.05, /0=1.0, ’/0=1.0

• Look for an excess of signals over background

Very low-mass dileptonsVery low-mass dileptons

0-30

90-140

140-200

200-300

Rdata

32

222

2

2

2

2

112

14

13

21)

M

m()m(F

m)

m

m(

m

m

dm

dN

Nee

eeeeee

e

ee

e

ee

ee −+−=α

Kroll-Wada Formula

phase space factor is unity for high pT

Compton

• Ratios of Minv bins to lowest one (Rdata)

• If no direct photons: the ratios become exactly what can be calculated from Dalitz decay formula above

• If excess over calculation: direct photons

Including Virtual PhotonsIncluding Virtual Photons


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excess ratio (measured/background)– Systematic error revisited and improved: pT-correlated: 7.5%, point-

by-point: 7.0%

• Consistent with Run2and very low-mass dilepton (~21% relative error to ratio)

Note that *dir / *incl +1 is slightly different from meas / background. Centrality range is different as well.Mass Range:0<Mee<30MeV/c2 (calculated from that in 90<Mee<300MeV/c2)

ResultsResults


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Overlaid with thermal + pQCD calc.

Additional ~10 % systematic error from inclusive included

• Very low mass dilepton ratio converted to direct photon spectrum

– Assumption: dir / incl = *dir / *incl (for Mee << M)

dir = *dir / *incl incl incl is real inclusive photon

D. d’Enterria, D. Perresounko, nucl-th/0503054

A Thermal Hint?A Thermal Hint?


36Direct photon in higher mass Direct photon in higher mass Dilepton?Dilepton?

• Contribution of direct photons converted into electron pairs?

• Try to see what it looks like

– Take the direct photon spectra

– Kroll-Wada’s formula to convert direct photon to electron-pair spectra

– Phase space factor considered• (1-mee

2/M2)3

– M = E, |F(mee)| = 1

– Acceptance filter for PHENIX is not applied

• Look at higher mass region.

Needs a detailed look with taking the acceptance into account.

0

Direct photon internal conversion

0-20% centralitypT>1.0GeV/c

Probably not significant compared to predicted thermally radiating dilepton.


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Cocktail comparisonCocktail comparison

• Data and cocktail absolutely normalized

•Cocktail from hadronic sources•Charm from PYTHIAPredictions are filtered in PHENIX acceptance

•Good agreement in p0 Dalitz•Continuum:hint for enhancement not significant within systematics

•What happens to charm?•Single e pt suppression•angular correlation???

• LARGE SYSTEMATICS!


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Data/cocktailData/cocktail

Measurement [10-5 counts/event]

Predictions[10-5 counts/event]

0.15-0.7 GeV/c2 17.8 ± 3.8 ± 1.50 12.3

1.1-2.5 GeV/c2 0.67 ± 0.50 ± 0.11 1.16


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Comparison with theoryComparison with theory

R.Rapp, Phys.Lett. B 473 (2000)R.Rapp, Phys.Rev.C 63 (2001)R.Rapp, nucl/th/0204003


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Total Charm Yield Total Charm Yield in Run2 Au+Auin Run2 Au+Au

• Binary scaling works well for total charm yield

• dNe/dy is fit to ANcollαα = 0.938+/-0.075+/-0.0018

• Coming soon: High statistic data in Run4 Au+Au

S.S. Adler, et al., PRL 94 082301


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Prompt Prompt in Run3 d+Au in Run3 d+Au

Suppression(?) in d going direction

Enhancement(?) in Au going direction

dAuSouth

NorthBeam direction


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Heavy flavor in Run3 d+AuHeavy flavor in Run3 d+Au

Minimum Biasnon-photonic electrons

PHENIX preliminary


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RRAAAA of heavy flavor electrons of heavy flavor electrons

Theory curves (1abc) from N. Armesto, et al., PRD 71, 054027

(2ab) from M. Djordjevic, M. Gyullasy, S.Wicks, PRL 94, 112301

PRL accepted recently (nucl-ex/0510047).

(1c) q_hat = 14 GeV2/fm

(1b) q_hat = 4 GeV2/fm

(1a) q_hat = 0 GeV2/fm

(2a) dNg / dy = 1000

(2b) dNg / dy = 3500

Clear evidence for strong medium effects!


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J/J/ΨΨ measurement measurement• PHENIX measured the J/ yield in p+p, d+Au, Au+Au and

Cu+Cu to understand the J/ production in each stage of collisions.

Base line for all measurementsσJ/as a function of rapidity, pT

Initial stage effect• Gluon shadowing

Nuclear medium effect• Nuclear absorption• Cronin effect

σJ/ as a function of rapidity, pT, XAu

p+p collisions

d+Au collisions


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• PHENIX measured the J/ yield in p+p, d+Au, Au+Au and Cu+Cu to understand the J/ production in each stage of collisions.

Au+Au collisionsCu+Cu collisions

Extract the medium effect• Color screening • Coalescence

σJ/ (yield) as a functionrapidity, pT

collision centralitycollision species (Au+Au/Cu+Cu)collision energy (200GeV/62.4GeV)

p+p/d+Au collisions

Note that feed down effect from c and ’ is also important.But they are not accessible with the current RHIC luminosity.

J/J/ΨΨ measurement measurement


46J/J/ΨΨ cross section in cross section in

p+pp+p • Cross section vs. rapidity and energy dependence

p-p J/Psi – PHENIX 200GeV

y

Integrated cross section σ = 2.61+-0.20(fit)+-0.26(abs) bGives a good base line for d+Au, Au+Au and Cu+Cu.

nucl-ex/0507032Accepted in PRL


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J/J/ΨΨ in d+Au Collisions in d+Au Collisions

gluons in Pb / gluons in p

X

Shadowing

Eskola, et al., Nucl. Phys. A696 (2001) 729-746.

AntiShadowing

Xd XAu

J/ inNorthy > 0

Xd XAu

J/ inSouthy < 0

rapidity y

South muon arm (y < -1.2) : –large XAu 0.090

Central arm (y 0) :–intermediate XAu 0.020

North muon arm (y > 1.2) : –small XAu 0.003

• Understand the cold matter effects– Gluon Shadowing

– Cronin effect (pT broadening)

– Nuclear Absorption

• Coverage of XAu in d+Au

at PHENIX


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J/J/ΨΨ in d+Au vs. p in d+Au vs. pTT

• Cronin effect (pT broadening)

Observation of pT broadening at RHIC.Initial state multiple scattering of partons

nucl-ex/0507032accepted in PRL


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ppTT broadening broadening

• Suppression factor α:

α vs. pT

• Comparison to E866 at s = 39 GeV.

xAu~ 0.01

xAu~ 0.003

xAu~ 0.1

ασσ )1972( ×= ppdAσdAu = σpp (2x197)α

Trend of pT broadening at RHIC is consistent with E866 results.



50Nuclear Absorption and Nuclear Absorption and ShadowingShadowing

• RdAu vs. rapidity, centrality, α vs. x coverage

E866: PRL 84, 3256 (2000)NA3: ZP C20, 101 (1983)

(in gold)

RdA

0

0.2

0.4

0.6

0.8

1.0

1.2

Rapidity

RdAu

Weak nuclear absorption : σ =1–3 mb (4.3 mb at SPS)Suppression increased weakly toward the central collisions.Weak shadowing (violation of XAu scaling) : α > 0.92



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Summary (d+Au J/Summary (d+Au J/ΨΨ measurements) measurements)• Observation of Cronin effect (pT broadening)

• Trend of Cronin effect is consistent with lowerenergy results.• Observation of nuclear absorption and shadowing effect.

– Nuclear absorption at RHIC is weak (1-3mb)compared to lower energy results (SPS, FNAL)– Shadowing effect is weak

• A modest baseline measurement for A+A collisions. • Further statistics are needed for the detail study

of cold matter effects.


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Invariant pInvariant pTT distributions distributions

J/ e+e- (Au+Au)

20-40%

40-93%

p+p

0-20%

20-40%

40-93%

J/ +- (Au+Au)Cu+Cu

Cu+Cu

Extraction of <pT2> by fitting with A(1+(pT/B)2)-6


53

Phys. Lett. B 561 (2003)

Feed down and J/Feed down and J/ΨΨ suppression suppression• Feed down from c and ’ is important.

30% from c and 10% from ’ (FNAL E705, HERA-B)

– Tdiss(’) Tdiss() 1.1 Tc << Tdiss(J/) 2 Tc (Lattice calc.)

– J/suppression at RHIC could be due to the melt of c and ’? (J/would survive at RHIC.)

The melt of c and ’ can explain Jsuppressionat SPS.

How about J/suppressionat RHIC?

Describe well up to mid-centraland more suppression at most central.Feed down is larger at RHIC?Melting of J/at most central?Need to study c and ’ production at RHIC (RHIC-2).

Recent Results from . . on Heavy Flavor and Electromagnetic Probes at RHIC

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