STAR Highlights II: Production and Energy Loss

1
STAR Highlights II Production and Energy Loss
of Strange and Heavy Quarks
Lijuan Ruan (for the STAR Collaboration) (Brookha
ven National Laboratory)

• Outline
• Motivation and introduction
• Hard probes
• High pT kaon production in pp and
  AA
• Non-photonic electron production in
  pp and AA
• e-h correlation access bottom
  contribution in pp
• 
  
• Quarkonia production J/? in pp,
  AA
• 
  ? in dAu
• Summary and outlook

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The STAR Detector 2? coverage at mid-rapidity
TPC, EMC, FMS, DAQ1000, Time of Flight, Heavy
Flavor Tracker, Muon Telescope Detector
3
Jet energy loss

• Physics goal at RHIC identify and study the
  properties of matter with partonic
• degrees of freedom.
• Hard probes identified particles at high pT,
  heavy flavor, jets
• Spectra in pp collisions at pTgt2 GeV/c
  convolution of PDF?pQCD?FF
• In AuAu collisions at RHIC Fragmentation
  energy loss at pT gt 6 GeV/c.
• Nuclear Modification Factor gluon density and
  transport coefficient

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To further understand energy loss mechanisms and
medium properties

• Color charge dependence g q (CA/CF9/4) protons
  versus pions
• g q jet conversion in the medium protons versus
  pions, kaons versus pions
• Flavor dependence light q versus heavy Q
  enon-photonic versus light hadrons
• Understand particle production mechanisms in pp
  reference
• STAR, PLB 637 (2006) 161, PLB 616 (2005) 8

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Kaon in 200 GeV pp at high pT
Spectra in pp collisions at pTgt2 GeV/c
convolution of PDF?pQCD?FF Charged and neutral
kaons are extended up to 15 GeV/c in pp
collisions. Charged and neutral kaons are
consistent provide constraints on FFs.
Low pT KS STAR Phys. Rev. C 75 (2007) 64901

• Y. Xus talk (Parallel Session 6)
  

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Measure fragmentation functions in pp

• Pythia reproduces K0S fragmentation functions OK,
  deviations observed for strange baryons

• A. Timmins talk (Parallel Session 1)
  

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Jet hadro-chemistry in AuAu and pp
STAR Preliminary
STAR Preliminary

• The final jet hadro-chemistry change was
  observed
• K/? (AuAu) gt K/? (pp) RAA(ppbar) ? RAA(K) gt
  RAA (?) RAA(?)
• Consistent with jet conversion mechanisms and/or
  modified enhanced parton splitting in the hot,
  dense medium S. Sapeta and U.A. Wiedemann,
  arXiv0707.3494

• Y. Xus talk (Parallel Session 6)
  

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Jet hadro-chemistry in AuAu and pp

• Model comparisons
• Need detailed modeling of enhanced parton
  splitting and jet conversion
• Expanding medium
• Improved fragmentation function, which our data
  will provide better constraints on.
• High pT K measurements in dAu, centrality
  dependence in AuAu and v2

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RAA of non-photonic electrons

• Non-photonic electrons show a similar magnitude
  of suppression as light hadrons in AuAu and
  CuCu collisions
• No D and B spectra measurements at RHIC at high
  pT
• Whats the real c and b contribution to single
  electrons?

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e-h correlations bottom contribution
B decay D decay red BD (total)
Extract bottom contribution from the
data/simulation(PYTHIA) comparison non-photonic
electron spectra has a significant contribution
from bottom Collisional dissociation of heavy
mesons, in-medium heavy resonance diffusion,
multi-body mechanisms might play an important
role for heavy quark energy loss A. Adil and I.
Vitev, Phys. Lett. B649, 139 (2007) H. van Hess,
V. Greco and R. Rapp, Phys. Rev. C 73 034913
(2006) W. Liu and C. M. Ko, nucl-th/0603004 Dire
ct D, B measurements are crucial
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color screening and sequential suppression of
quarkonia
J/? suppression at low pT maybe from excited
stats (?, ?c) F. Karsch, D. Kharzeev and H.
Satz, PLB 637, 75 (2006) B. Alessandro et al.
(NA50), Eur. Phys. J. C 39 (2005) 335 R. Arnaldi
et al. (NA60), Quark Matter 2005 PHENIX
Phys.Rev.Lett.98, 232301,2007. 60 from direct
J/? not suppressed 30 ?c and 10 ?
dissociated
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AdS/CFT with hydro
Hot wind dissociation
Can we observe direct J/? suppression? Hot
wind dissociation ? high pT direct J/?
suppression Do we understand J/? production
mechanisms in pp collisions?
H. Liu, K. Rajagopal and U.A. Wiedemann PRL 98,
182301(2007) and hep-ph/0607062 M. Chernicoff, J.
A. Garcia, A. Guijosa hep-th/0607089
T. Gunji, QM08
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J/y spectra in pp and CuCu at 200 GeV
Model comparisons Color singlet model (CS)
direct NNLO still miss the high pT part. P.
Artoisenet et al., Phys. Rev. Lett. 101, 152001
(2008), and J.P. Lansberg private communication.
LO CS color octet (CO) better agreement with
the measurements, leave little room for higher
charmonium states and B feeddown contribution. G.
C. Nayak, M. X. Liu, and F. Cooper, Phys. Rev.
D68, 034003 (2003), and private
communication. CS and LO CSCO have different
power parameters ? different diagram
contribution? power parameter n8 for
NNLO CS n6 for LO CSCO
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xT scaling in pp collisions

• xT scaling
• ? and proton at pTgt2 GeV/c n6.60.1 PLB 637,
  161(2006)
• J/? at high pT n5.60.2 (the power parameter
  close to CSCO prediction)
• 3. Soft processes affect low pT J/? production

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Nuclear modification factor RAA

• Consistent with no suppression at high pT
  RAA(pTgt5 GeV/c)
• 1.4 0.40.2
• RAA(pTgt5GeV/c) gt 0.6
• (97 C.L.) ?
• RAA increase from low pT to high pT

arXiv 0904.0439
STAR Preliminary

• Jet quenching strong open charm suppression.
  J/? is likely to be produced dominantly through
  CS states A. Adil and I. Vitev, Phys. Lett. B649,
  139 (2007), and I. Vitev private communication
  S. Wicks et al., Nucl. Phys. A784, 426 (2007),
  and W. A. Horowitz private communication.
• Contrast to AdS/CFT Hydro prediction (99 C.L.)
  H. Liu, K. Rajagopal and U.A. Wiedemann PRL 98,
  182301(2007)T. Gunji, J. Phys.G 35, 104137
  (2008)
• Formation time, gluon dissociation,
  recombination, B reproduces the trend
• X. Zhao and R. Rapp (2007), arXiv0712.2407.

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Constrain bottom yields
STAR Preliminary
arXiv 0904.0439
STAR Preliminary

• correlations shows low B contribution (13 ? 5)
• can used to further constrain B yields

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Constrain bottom yields
STAR Preliminary
arXiv 0904.0439
STAR Preliminary

• pQCD predicts significant B?J/?
• correlations shows low B contribution
• can be used to further constrain B yields
• M. Cacciari, P. Nason and R. Vogt PRL
  95(2005),122001 CLEO collaboration PRL
  89(2002),282001

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The future measurements

• High pT (gt5 GeV/c) J/? power parameter n6 in
  pp RAA consistent with unity
• dominantly produced through CS states, formation
  time effect, cross
• section contrast to current NNLO CS pQCD
  calculations.
• To understand the production mechanism at high pT
  and medium
• properties using medium to understand the J/?
  production
• mechanism in pp
• Different collision system AuAu (RAA)
• Cold nuclear medium effect dAu
• Intrinsic charm contribution at large xF
• forward/backward measurements
• Different energy pp 500 GeV
• Correlations
• Spin alignment of J/?
• Higher states ?c, ?
• J/? v2
• Upsilon

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Upsilon?production in dAu
RdAu 0.98 0.32 (stat.) 0.28 (sys.)

• Run8 dAu 200 GeV
• High luminosity 32nb-1
• Low material in front of TPC
• L0L2 Upsilon trigger

• Consistent with Nbin scaling
• Consistent with anti-shadowing
• calculations

• R. Reeds talk (Parallel Session 5)
  

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Future dramatic improvement of J /? at low pT
PHENIX Acceptance hlt0.35,
f2p/2 STAR TOF-Upgrade Acceptance hlt0.9,
f2p J/y yields from 1 billion minbias AuAu
events 43.8x10-9/0.040x1092920.51.80.5
144,000?0.3 v2 error sJ/y spp N
Nbin e y RAA
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High luminosity for ? J/?
STAR high pT J/?
MTD excellent mass resolution for ?
separate different ? states
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Summary

• Understand particle production mechanisms in pp,
  constrain FFs
• Kaon pT spectra up to high pT 15 GeV/c
• Fragmentation function measurements
• Characteristics of jet quenching in hot, dense
  medium
• RAA(ppbar) ? RAA(K) gt RAA(?)RAA(?) at pTgt6
  GeV/c, jet conversion
• RAA(?)RAA(e) significant bottom contribution
  from e-h correlation at high pT, challenging pQCD
  energy loss calculations
• Quarkonia production mechanisms in pp and AA and
  their medium properties
• High pT J/? power parameter n6 in pp RAA
  consistent with unity dominantly produced
  through CS states, formation time effect, cross
  section contrast to current NNLO CS pQCD
  calculations
• ? cross section in dAu consistent with Nbin
  scaling
• EOS, thermalization
• Future measurements from TOF, HFT, MTD
• Precise D and B measurements energy loss
  mechanisms, thermalization
• J/? measurements from low to high
  pT,different ?states color screening, J/psi
  production mechanisms, EOS Thanks to the
  STAR Collaboration !