Transcript Document

STAR Heavy Flavor Measurements in Heavyion Collisions
W. Xie for STAR Collaboration
(PURDUE University, West Lafayette)
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
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Quarkonia Suppression: “Smoking Gun” for QGP
c
• Low temperature
c
• Vacuum
J/y
• High temperature
c
c
d
d
Color Screening
D+
D-
• High density
(screening effect take place)
Sequential meltinga QGP thermometer
H. Satz, NPA 783 (2007) 249c.
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The life of Quarkonia in 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)
c
J/y
• Hot/dense medium effect
– J/y,  dissociation, i.e. suppression
– Recombination from uncorrelated charm pairs
c
c
D+
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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
MTD
MRPC ToF barrel
EMC barrel
EMC End Cap
FMS
BBC
FPD
TPC
FHC
PMD
DAQ1000
HLT
FTPC
HFT
FGT
Completed
Ongoing
R&D
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Signals Observed in STAR
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.
D* p+p 200 GeV
D0 Au+Au 200 GeV
forward J/ψ
D* p+p 500 GeV
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STAR Charmonia Measurements
e-/-
e+/+
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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
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RAA vs. pT vs. Npart





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
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J/y flow: more discriminating power
J/y
Yan,Zhuang,Xu
PRL 97, 232301 (2006)
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.
z
y
x
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J/y spectra in 200GeV Au+Au collisions
Broad pT coverage
from 0 to 10 GeV/c
Phys. Rev. Lett. 98, 232301 (2007)
J/y spectra
significantly softer
than the prediction
from light hadrons
 Much smaller
radial flow because
it’s too heavy?
 Regeneration at
low pT?
See Hao Qiu’s talk this afternoon for details
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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 Hao Qiu’s talk this afternoon for details
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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
See A. Kesich’s talk for details
STAR
Preliminary
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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
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STAR Open Charm Measurements
K+
D0
e-/-
l
K+
D0
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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:
𝑑𝜎
𝑐𝑐
| 𝑦=0
𝑑𝑦
(𝑝 + 𝑝) = 170 ± 45 (𝑠𝑡𝑎𝑡. ) +38
−59 𝑠𝑦𝑠. 𝜇b
 The charm total cross section is extracted as:
𝜎𝑐𝑐 = 797 ± 210 𝑠𝑡𝑎𝑡. +208
−295 (𝑠𝑦𝑠) 𝜇b
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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
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Charm cross section vs Nbin
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.) b
Total cross section:
876 ± 103 (stat.) ± 211 (sys.) b
[1]
[2]
[3]
[4]
STAR d+Au: J. Adams, et al., PRL 94 (2005) 62301
FONLL: M. Cacciari, PRL 95 (2005) 122001.
NLO: R. Vogt, Eur.Phys.J.ST 155 (2008) 213
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.
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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)
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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.
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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+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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Summary for the STAR Measurements
The charm cross section per nucleon-nucleon 200 GeV
collision at mid-rapidity
𝑑𝜎
𝑐𝑐
| 𝑦=0
𝑑𝑦
(𝑝 + 𝑝) = 170 ± 45 (𝑠𝑡𝑎𝑡. ) +38
−59 𝑠𝑦𝑠. 𝜇b
𝑑𝜎
𝑐𝑐
| 𝑦=0
𝑑𝑦
(Au + Au) = 186 ± 22 𝑠𝑡𝑎𝑡. ± 30(𝑠𝑦𝑠. ) ± 18(𝑛𝑜𝑟𝑚. ) mb
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
MTD (MRPC)
 See details in Yifei Zhang’s talk next
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backup
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D0 signal in p+p 200 GeV
arXiv:1204.4244.
𝐷0 𝐷0 → 𝐾 ∓ 𝜋 ±
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.
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D* signal in p+p 200 GeV
𝑫∗± → 𝑫𝟎 𝑫𝟎 + 𝝅± → 𝑲∓ 𝝅± + 𝝅±
arXiv:1204.4244.
Background recomstruction:
• 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.
 Wrong sign:
 D0 and -, D0 and +
 Side band:
 1.72< M(K) < 1.80 or
 1.92 < M(K) < 2.0 GeV/c2
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