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//Talk/2005/02icpaqgp05//Charm Production Thermalization Charm Production Thermalization

at RHICat RHIC

Nu Xu

Lawrence Berkeley National Laboratory

Many Thanks to Organizers!

X. Dong, H. Huang, H.G. Ritter, K. Schweda, A. Tai, Z. XuE.L. Bratkovskaya, L. Grandchamp, J. Raufeisen, R. Vogt

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OutlineOutline

Motivation

Charm production in p+p and d+Au collisions at RHIC

Charm flow measurements (preliminary)

Summary & Outlook

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Equation of State

€

∂μTμν = 0

∂μ j μ = 0 j μ (x) = n(x)uμ (x)

T μν = ε(x) + p(x)[ ]uμ uν − gμν ∗p(x)

Equation of state:

- EOS I : relativistic ideal gas: p = /3- EOS H: resonance gas: p ~ /6- EOS Q: Maxwell construction:

Tcrit= 165 MeV, B1/4 = 0.23 GeV

lat=1.15 GeV/fm3

P. Kolb et al., Phys. Rev. C62, 054909 (2000).

With given degrees of freedom, the EOS - the system response to the changes of the thermal condition - is fixed by its p and T ().

Energy density GeV/fm3

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High-Energy Nuclear CollisionsHigh-Energy Nuclear Collisions

Initial Condition - initial scatterings - baryon transfer - ET production - parton dof

System Evolves - parton interaction - parton/hadron expansion

Bulk Freeze-out - hadron dof - interactions stop

jets

J/ D

K, K*

p

d, HBT

elliptic flow velliptic flow v22

radial radial flowflow TT

Q2

time

partonic scatterings?early thermalization?

TTCC

TTchch

TTfofo

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Suppression and Correlation

In central Au+Au collisions: hadrons are suppressed and back-to-back ‘jets’ are disappeared. Different from p+p and d+Au collisions.

Energy density at RHIC: > 5 GeV/fm3 ~ 300

Parton energy loss: Bjorken 1982(“Jet quenching”) Gyulassy & Wang 1992…

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Collectivity, Deconfinement at RHIC

- v2, spectra of light hadrons and multi-strange hadrons - scaling of the number of constituent quarks

At RHIC: Partonic collectivity has been attained

Deconfinement has has been attained

PHENIX: PRL91, 182301(03) STAR: PRL92, 052302(04)

S. Voloshin, NPA715, 379(03)Models: Greco et al, PRC68, 034904(03)X. Dong, et al., Phys. Lett. B597, 328(04).….

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QCD Energy ScaleQCD Energy Scale

s-quark mass ~ 0.2 GeV, similar to values of TC critical temperature QCD QCD scale parameter TCH chemical freeze-out temperature

= 4f chiral breaking scale

mC

c-quark mass ~ 1.2 - 1.5 GeV >> QCD -- pQCD production - parton density at small-x -- QCD interaction - medium properties

Rcc ~ 1/mC => color screening J/ => deconfinement and thermalization

u-, d-, s-quarks: light-flavors || c-, b-quarks: heavy-flavorsheavy-flavors

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Why Charm?Why Charm?

1) Charm-quark’s constituent mass is very close to its current mass

2) The value of the charm-quark mass is much higher than the excitation of the system created in high-energy nuclear collisions

3) If open charm-quarks reaches kinetic equilibrium, coalescence process becomes possible for Charmonium formation and open-charm hadrochemistry

Charm-quarks constituent the ideal probe to study the Charm-quarks constituent the ideal probe to study the hot-dense medium created at RHIChot-dense medium created at RHIC

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J/J/ via coalescence via coalescence

J/J/ in central AA collisions, due to interaction with light flavors, values of mean pT decrease and yields increase deconfinement and thermalization for light flavors

Grandchamp and Rapp, NPA715, 545(03); hep-ph/0209141(02)

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Open-/closed-charm hadron yieldsOpen-/closed-charm hadron yieldsA. Andronic, P. Braun-Munzinger, K. Redlich, J. Stachel, Phys.Lett. B571 , 36(03).

L. Grandchamp and R. Rapp, Phys. Lett. B523 , 60(01).

(1) open charm cross; (3) medium effects ( properties);(2) direct pQCD production; (4) absorption (color screening) Model results are different, centrality dependence measurements are important!

RHIC

RHIC

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Charm Measurements

PHENIX: Electrons and MuonsSTAR: Electrons and directly reconstructed Ds

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STAR: TPC & MRPC-TOF

TPC dE/dx PID: pion/kaon: pT ~ 0.6 GeV/c; proton pT ~ 1.2 GeV/c

A new technology -Multi-gap Resistive Plate Chamber (MRPC), adopted from CERN-Alice

A prototype detector of time-of-flight (TOFr) was installed in Run3

One tray: ~ 0.3% of TPC coverage

Intrinsic timing resolution: ~ 85 pspion/kaon ID: pT ~ 1.7 GeV/cproton ID: pT ~ 3 GeV/c

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DD00 direct reconstruction direct reconstruction

Event mixing method:C. Adler et al., Phys. Rev. C66, 061901(R)(2002)H. Zhang, J. Phys. G30, S577(2004)

First Direct Open CharmReconstruction at RHIC

STAR Preliminary

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%)2.9(KD →±

%)8.3(%),68( 00* KDDD s →→±

%)2.6)((00 −++−→ ρKD

%)8.3(0 +−→ KD

D mesons measured at STAR

STAR Preliminary

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Hadron identification: STAR Collaboration, nucl-ex/0309012

STAR TOFr PIDSTAR TOFr PID

Electron identification: TOFr |1/ß-1| < 0.03 TPC dE/dx electrons!!!

electrons

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Electron Spectra [ cElectron Spectra [ c(b)(b) e+x ] e+x ]

An increasing excess found at higher pT region, pT > 1.0 GeV/c, Expected contribution of semi-leptonic decays from heavy flavor hadrons

STAR: nucl-ex/0407006

STAR Preliminary

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Consistent in D measurementsConsistent in D measurements

Directly reconstructed D mesons

D and electron spectra are consistent!

STAR: nucl-ex/0404029 STAR Preliminary

Electrons from D decay

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Combining FitsCombining Fits

Combined fit forD0 and electrons

PYTHIA: MSEL = 1, CTEQ5M1

Good agreement between D0 and electrons spectra!d+Au and p+p do not show significant nuclear effect

STAR PRL in print

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Open charm production at RHICOpen charm production at RHIC

- First reconstructed open charm spectrum at RHIC- pQCD pT spectra are steeper, total cross section is smaller by a factor of 3-5- STAR data: PRL in print, nucl-ex/0406007, nucl-ex/0404029- model results: R. Vogt, 2004

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Open charm production at RHICOpen charm production at RHIC

1) d/dy : a factor from model like Pythia. At 200 GeV, the factor 4.7 was used at STAR.

2) A strong dependent on the method of fragmentation in charm pT spectra observed, but not on rapidity distributions.

J. Raufeisen and J. Peng, Phys.Rev. D67, 054008(2003)HSD: Phys. Rev. C67 , 054905(2003).

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y

x

py

px

coordinate-space-anisotropy momentum-space-anisotropy

Anisotropy Parameter vAnisotropy Parameter v22

€

=⟨y 2 − x 2⟩⟨y 2 + x 2⟩

v2 = cos2ϕ , ϕ = tan−1(py

px

)

Initial/final conditions, EoS, degrees of freedom

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Non-photonic electron v2

STAR: 0-80% (F.Laue SQM04) PHENIX: Minimum bias statistical error only HSD: E. Bratkovskaya et al., hep-ph/0409071 X. Dong, S. Esumi, et al., Phys. Lett. B597, 328(2004).

corrected for e± from decay M. Kaneta et al, J.Phys. G30, S1217(04)

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Summary Summary

1) Open charm yields measured in both 200GeV p+p and d+Au collisions. No evidence of deviation from binary collision scaling in d+Au collisions

2) Perturbative calculations under predicted both yields and spectrum shape. Hadronization process not under control

3) Study open charm v2 and J/ yields to address thermalization issues at RHIC.

4) μ-vertex upgrades Phenix and STAR - open charm: precision measurements on spectra and v2

- resonances with both hadronic & leptonic decays

€

c ctotal =700 −1200 (μb)

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STAR STAR μμ-vertex detector-vertex detector

H. Wieman et al., STAR Collaboration