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W. Xie for STAR Collaboration (PURDUE University, West Lafayette). STAR Heavy Flavor Measurements in Heavy-ion Collisions. Outline : Quarkonia Measurements in p+p , d+Au and Au+Au collisions Open Charm Measurement D meson direct reconstruction. Non-photonic electron

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star heavy flavor measurements in heavy ion collisions

W. Xie for STAR Collaboration

(PURDUE University, West Lafayette)

STAR Heavy Flavor Measurements in Heavy-ion Collisions

  • 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.

UIC HF Workshop 2012

quarkonia suppression smoking g un for qgp

c

c

d

Quarkonia Suppression: “Smoking Gun” for QGP
  • Low temperature
  • Vacuum

J/y

  • High temperature
  • High density
  • (screening effect take place)

d

Sequential meltingaQGP thermometer

H. Satz, NPA 783 (2007) 249c.

D-

D+

the life of quarkonia in the medium can be complicated

c

c

c

The life of Quarkoniain the Medium can be Complicated
  • 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

J/y

D+

important to study open heavy flavor production
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.
slide6

The STAR Detector

EMC barrel

MTD

MRPC ToF barrel

EMC End Cap

FMS

BBC

FPD

TPC

FHC

PMD

FTPC

Completed

DAQ1000

Ongoing

R&D

HFT

FGT

HLT

6

signals observed in star
Signals Observed in STAR
  • STAR can measure heavy flavor
  • of all different kind
    • (J/ψ, D0, D*, electron …)
  • in broad pTrange.
  • at both mid and forward rapidity
  • in all collision species.

D* p+p 200 GeV

D0Au+Au 200 GeV

forward J/ψ

D* p+p 500 GeV

j y suppression enhancement in 200gev d a and a a and collisions
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)

Phys.Rev.C80:041902,2009

r aa vs p t vs npart
RAA vs. pT vs. Npart
  • Consistent with unity at high pT in (semi-) peripheral collisions
  • Systematically higher at high pTin all centralities
  • Suppression in central collisions at high pT
  • System size dependence due to J/y formation time effect?
  • Escaping at high pT?

See HaoQiu’s talk this afternoon for details

slide11

J/

z

y

x

Yan,Zhuang,Xu

PRL 97, 232301 (2006)

J/y flow: more discriminating power

PHENIX NPE v2: arXiv:1005.1627v2

  • 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.
j y spectra in 200gev au au collisions
J/y spectra in 200GeV Au+Au collisions
  • 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 HaoQiu’s talk this afternoon for details

j y elliptic flow v 2
J/y elliptic flow v2

STAR Preliminary

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

See HaoQiu’s talk this afternoon for details

the s qgp is complicated
The sQGP is Complicated

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.

STAR Preliminary

STAR Preliminary

STAR Preliminary

See A. Kesich’s talk for details

a quick glimpse of star upsilon measurements
A Quick Glimpse of STAR Upsilon Measurements

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

  • Consistent with the melting of all excited states.

See A. Kesich’s talk for details

d 0 and d p t spectra in p p 200 gev
D0 and D* pT spectra in p+p 200 GeV

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|ccy=0 × F × spp

F = 4.7 ± 0.7 scale to full rapidity.

spp(NSD) = 30 mb

arXiv:1204.4244.

[1] C. Amsler et al. (PDG), PLB 667 (2008) 1.

[2] FONLL: M. Cacciari, PRL 95 (2005) 122001.

  • The charm cross section at mid-rapidity is:
  • The charm total cross section is extracted as:
  • b

|

17

d 0 signal in au au 200 gev
D0 signal in Au+Au 200 GeV

YiFei Zhang, JPG 38, 124142 (2011)

  • 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

18

charm cross section vs n bin
Charm cross section vsNbin

YiFei Zhang, JPG 38, 124142 (2011)

arXiv:1204.4244.

All of the measurements are consistent.

Year 2003 d+Au : D0 + e

Year 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.) mb

Total cross section:

876 ± 103 (stat.) ± 211 (sys.) mb

[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.

Charm cross section follows number of binary collisions scaling =>

Charm quarks are mostly produced via initial hard scatterings.

19

d 0 r aa compared with alice result
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)

20

non photonic electron measurements
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

STAR: PRL 106, 159902 (2011)

PHENIX: arXiv:1005.1627v2

  • See M. Mustafa talk in the afternoon.
summary for the star measurements
Summary for the STAR Measurements
  • 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+Aucollisions
  • 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.
summary for the star measurements1
Summary for the STAR Measurements
  • 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.

|

|

23

future of heavy flavor measurement at star
Future of Heavy Flavor Measurement at STAR

MTD (MRPC)

  • See details in Yifei Zhang’s talk next
d 0 signal in p p 200 gev
D0 signal in p+p 200 GeV

arXiv:1204.4244.

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.

26

d signal in p p 200 gev
D* signal in p+p 200 GeV

arXiv:1204.4244.

  • Background recomstruction:
  • Wrong sign:
    • D0 and -, and +
  • Side band:
    • 1.72< M(K) < 1.80 or
    • 1.92 < M(K) < 2.0 GeV/c2
  • 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.

27