STAR Heavy Flavor Measurements in Heavy-ion Collisions

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Outline: Quarkonia Measurements in

p+p, d+Au and Au+Au collisions

Open Charm Measurement D meson direct reconstruction. Non-photonic electron

Summary of the Present Results.

Future STAR Heavy Flavor Program.

06/18/2012 UIC HF Workshop 2012

W. Xie for STAR Collaboration(PURDUE University, West Lafayette)

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Quarkonia Suppression: “Smoking Gun” for QGP

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Color Screening

cc

cc

J/y

D+

d

• Low temperature• Vacuum

• High temperature• High density

(screening effect take place)

Sequential meltinga QGP thermometerH. Satz, NPA 783 (2007) 249c.

d

D-

The life of Quarkonia in the Medium can be Complicated

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• Observed J/y is a mixture of direct production+feeddown (R. Vogt: Phys. Rep. 310, 197 (1999)). – All J/y ~ 0.6J/y(Direct) + ~0.3 cc + ~0.1y’– B meson feed down.

• Important to disentangle different component

• Suppression and enhancement in the “cold” nuclear medium– Nuclear Absorption, Gluon shadowing, initial state energy loss, Cronin

effect and gluon saturation (CGC)

• Hot/dense medium effect – J/y, dissociation, i.e. suppression– Recombination from uncorrelated charm pairs D+

cc

cJ/y

Important to Study Open Heavy Flavor Production

• A good reference to J/Ψ suppression or enhancement.– Same or similar initial state effect.

• CGC, Shadowing, initial state energy loss, etc. – Large cross section (compared to J/ψ).

• Probability for recombination.• Accurate reference measurements.

• One of the important probes complimentary to J/ψ measurements – Interactions between heavy quark and medium are quite different

from the ones for light quarks• gluon radiation, collisional energy loss, collisional disassociation, etc

– allow further understanding of the medium properties.

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The STAR Detector

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MRPC ToF barrel

BBC

PMD

FPD

FMS

EMC barrelEMC End Cap

DAQ1000 Completed

TPC

FTPC

FGT Ongoing R&D

FHC

HLT HFT

MTD

Signals Observed in STAR

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STAR can measure heavy flavor• of all different kind

• (J/ψ, D0, D*, electron …)• in broad pT range.• at both mid and forward rapidity• in all collision species.

forward J/ψ

D0 Au+Au 200 GeV

D* p+p 200 GeV

D* p+p 500 GeV

STAR Charmonia Measurements

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e-/-

e+/+

J/y Suppression/Enhancement in 200GeV d+A and A+A and Collisions

d+Au Collisions:• Nice consistency with PHENIX

Cu+Cu Collisions: RAA(p>5 GeV/c) = 1.4± 0.4±0.2 RAA seems larger at higher pT. Model favored by data:

2-component: nucl-th/0806.1239 Incl. color screening, hadron phase

dissociation, coalescence, B feeddown.

Model unfavored by the data: AdS/CFT+Hydro:

JPG35,104137(2008)

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Phys.Rev.C80:041902,2009

RAA vs. pT vs. Npart

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Consistent with unity at high pT in (semi-) peripheral collisions Systematically higher at high pT in all centralities Suppression in central collisions at high pT

System size dependence due to J/y formation time effect? Escaping at high pT ?

See Hao Qiu’s talk this afternoon for details

J/y flow: more discriminating power

If charm quark flows. J/Psi from recombination also flow. If the observation is consistent with zero flow, it could mean

J/psi does not flow OR Flow is small due to mass ordering effect OR Recombination is not a dominant process.

Yan,Zhuang,XuPRL 97, 232301 (2006)

J/y

PHENIX NPE v2: arXiv:1005.1627v2

xy z

J/y spectra in 200GeV Au+Au collisions

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Broad pT coverage from 0 to 10 GeV/c

J/y spectra significantly softer than the prediction from light hadrons Much smaller

radial flow because it’s too heavy?

Regeneration at low pT?

Phys. Rev. Lett. 98, 232301 (2007)

See Hao Qiu’s talk this afternoon for details

STAR Preliminary

J/y elliptic flow v2

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disfavors the case that J/Ψ with pT > 2GeV/c is produced dominantly by coalescence from thermalized charm and anti-charm quarks.

See Hao Qiu’s talk this afternoon for details

STAR Preliminary

STAR Preliminary

STAR Preliminary

The sQGP is Complicated

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We thus need more probes, other than charms, to have a more complete picture of its properties, e.g. Upslions. Cleaner Probes compared to J/psi: recombination can be neglected at RHIC Grandchamp, Sun, Van Hess, Rapp, PRC 73, 064906 (2006)

Final state co-mover absorption is small.

See A. Kesich’s talk for details

A Quick Glimpse of STAR Upsilon Measurements

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Consistent with the melting of all excited states.

Models from M. Strickland and D. Bazow, arXiv:1112.2761v4

See A. Kesich’s talk for details

STAR Open Charm Measurements

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D0

K+

+

l

K-

e-/-D0

The charm cross section at mid-rapidity is:

The charm total cross section is extracted as: b

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D0 and D* pT spectra in p+p 200 GeV

[1] C. Amsler et al. (PDG), PLB 667 (2008) 1. [2] FONLL: M. Cacciari, PRL 95 (2005) 122001.

arXiv:1204.4244.

D0 scaled by Ncc / ND0 = 1 / 0.56[1]

D* scaled by Ncc / ND* = 1 / 0.22[1]

Consistent with FONLL[2] upper limit.Xsec = dN/dy|cc

y=0 × F × spp

F = 4.7 ± 0.7 scale to full rapidity.spp(NSD) = 30 mb

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D0 signal in Au+Au 200 GeV

Year 2010 minimum bias 0-80% 280M Au+Au 200 GeV events.

8-s signal observed. Mass = 1863 ± 2 MeV (PDG value is 1864.5 ± 0.4 MeV) Width = 12 ± 2 MeV

YiFei Zhang, JPG 38, 124142 (2011)

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Charm cross section vs Nbin

Charm cross section follows number of binary collisions scaling =>Charm quarks are mostly produced via initial hard scatterings.

All of the measurements are consistent.Year 2003 d+Au : D0 + eYear 2009 p+p : D0 + D*Year 2010 Au+Au: D0

Assuming ND0 / Ncc = 0.56 does not change.Charm cross section in Au+Au 200 GeV:Mid-rapidity:186 ± 22 (stat.) ± 30 (sys.) ± 18 (norm.) bTotal cross section:876 ± 103 (stat.) ± 211 (sys.) b[1] STAR d+Au: J. Adams, et al., PRL 94 (2005) 62301[2] FONLL: M. Cacciari, PRL 95 (2005) 122001.[3] NLO:  R. Vogt, Eur.Phys.J.ST 155 (2008) 213   [4] PHENIX e: A. Adare, et al., PRL 97 (2006) 252002.

YiFei Zhang, JPG 38, 124142 (2011)arXiv:1204.4244.

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D0 RAA compared with Alice result

YiFei Zhang, JPG 38, 124142 (2011) ALICE results shows D

meson is suppressed at high pT.

More luminosity and detector upgrade are needed from STAR to reach high pT.

At present, NPE is the key to study high pT charm and bottom production.

A. Rossi, JPG 38, 124139 (2011)

Non-photonic Electron Measurements

DGLV: Djordjevic, PLB632, 81 (2006)

BDMPS:Armesto, et al.,PLB637, 362 (2006)

T-Matrix:Van Hees et al., PRL100,192301(2008).

Coll. Dissoc. R. Sharma et al., PRC 80, 054902(2009).

Ads/CFT: W. Horowitz Ph.D thesis.

RL.+ Coll. J. Aichelin et al., SQM11

21 See M. Mustafa talk in the afternoon.

STAR: PRL 106, 159902 (2011)PHENIX: arXiv:1005.1627v2

Summary for the STAR Measurements

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No suppression for J/psi at high pT (5-10 GeV/c) in 200GeV Cu+Cu and peripheral Au+Au collisions,

suppression at high pT in central Au+Au collisions

J/psi suppression at high pT less than that at low pT

J/psi v2 measurements are consistent with zero, disfavor production at pT > 2 GeV/c dominated by coalescence from thermalized charm quarks

Upsilon measurement are consistent with 2S and 3S state melting.

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The charm cross section per nucleon-nucleon 200 GeV collision at mid-rapidity

Charm cross sections at mid-rapidity follow number of binary collisions scaling, which indicates charm quarks are mostly produced via initial hard scatterings.

D0 nuclear modification factor RAA is measured. No obvious suppression observed at pT < 3 GeV/c.

Large suppression of high-pT non-photonic electron production is observed.

A real challenge to our understanding of energy loss mechanism.

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Summary for the STAR Measurements

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Future of Heavy Flavor Measurement at STAR

MTD (MRPC)

See details in Yifei Zhang’s talk next

backup

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D0 signal in p+p 200 GeV

B.R. = 3.89%

p+p minimum bias 105 M

4-s signal observed.

Different methods reproduce combinatorial background.

Consistent results from two background methods.

𝐷0 (𝐷0 )→𝐾∓𝜋±arXiv:1204.4244.

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D* signal in p+p 200 GeV

• Minimum bias 105M events in p+p 200 GeV collisions.

• Two methods to reconstruct combinatorial background: wrong sign and side band.

• 8-s signal observed.

Background recomstruction:

Wrong sign: D0 and -, and +

Side band: 1.72< M(K) < 1.80 or 1.92 < M(K) < 2.0 GeV/c2

𝑫∗±→𝑫𝟎 (𝑫𝟎 )+𝝅±→𝑲∓𝝅±+𝝅±

arXiv:1204.4244.