Jet Correlations at RHIC Zhangbu Xu BNL

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Identified high pt spectra and Open charm from
STAR

• Identified hadrons at high pT
• dE/dx at relativistic rise
• p, p Spectra in dAu, AuAu (pTgt5 GeV/c)
• Open Charm at RHIC
• Charm Cross Section and Spectra
• Compatibility of Current Measurements
• Need detector upgrades

• Zhangbu Xu (BNL)
• for the STAR Collaboration

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Time Projection Chamber 45 padrow, 2 meters
(radius), s(dE/dx)?8, -1lt?lt1 Multi-gap Resistive
Plate Chamber TOFr 1 tray (1/200), s(t)85ps
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dE/dx at higher pT
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?-(Kp) Separation

• 3 Gauss fits dE/dx(p)gt1.3dE/dx(K)dE/dx(p) as
  normal Gauss s1, mean0
• ?-(Kp) Separation 1.5-2?

• Worst Contamination 1-3 at 50 Eff , 10 at
  70-90 Eff

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Pion Spectra
p/ p- ratio is about 1 pbar/p 0.5

• TPCTOF
• Pion 0.-10 GeV/c
• Kaon 0.2-3GeV/c
• Proton 0.2-? GeV/c

• TPC
• Pion 0-0.6GeV/c
• Kaon 0.2-0.6GeV/c
• Proton 0.2-1 GeV/c

• TOF
• Pion 0.2-1.6GeV/c
• Kaon 0.2-1.6GeV/c
• Proton 0.2-3 GeV/c

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p? Nucl. Mod. Factor

• RCP h- 20 higher than p- pT3-4
  GeV/cconsistent with h/pi ratio
• Vitev prediction at dN/dy650
• TOFr agrees with dE/dx p-
• ISR pp parametrization same as PHENIX
• Estimated Syst. Error 5-10

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Higher ? AuAu_at_62
dE/dx in dAu_at_200
hlt0
hgt0
h
h-
Different particle composition visible!!!
Better dE/dx resolution longer track, shorter
drift distance
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p- in dAu
Identified pions similar to inclusive hadrons
Au-side gt d-side in all pT (upto 5 GeV/c) Still
many things to do in the near future!!!
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Particle ID above 10 GeV/c
Charged hadrons statistics limited Neutral
pions triggered in EMC (A. Mischke (STAR)
nucl-ex/0412045) pp reference work in progress
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Proton PID at high pT
h-/h
Central AuAu 200 GeV

• dE/dx separation quite large at pT 10 GeV/c
• Ratios of inclusive hadrons confirm particle
  compositions and ability to identify particles

h/h-
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Antiparticle/Particle Ratios
p/p- ratio constant vs pT ?p/p ratio consistent
with flat in pT Run4 x10 more data small
errors, higher pT
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Baryon Production
Central AuAu 200 GeV
Proton (relative) yield decreases rapidly beyond
pT3 GeV/c!
pion, proton spectra at high pT PID jet
correlations
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Effects related to Open Charm

• Radiation Energy Loss
• Collision Energy Loss
• Dead Cone Effect
• Ter-Mikayelian Effect
• Transition Radiation
• Flow (radial elliptic)
• (quark) Coalescence
• Death of dead cone All these happen at
  intermediate pTEmphasize on experimental
  measurements

Down Down Up Up Down Up Up Down
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Charm Total Cross Section
Data STAR/PHENIX x2 (lt2s)? Lower Energies
inconsistent? Models PHENIX consistent with
default PYTHIA,pQCD STAR gt3
above ? Energy dependence mR and mF? Need
smaller errors to constrain pQCD and determine
the effects in Cosmic Ray Showers
X. Dong USTC
Can we confirm or rule out Cosmic Ray experiments
(Pamir, Muon, Tian Shan) under similar
conditions?
Pamir, Nuovo Cim 24c (2001) 557 NPB 122(2003)
353c
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Combine STAR/PHENIX Charm
X. Dong USTC
STAR PRL 94(2005) PHENIX pp (QM04) S.
Kelly et al. JPG30(2004) S1189
Discrepancy between STAR and PHENIX should be
resolved! J. Stachel, ICPAQGP05 Summary talk
No discrepancy? scc1.1?0.1 ? 0.3 mb STAR (1.4)
PHENIX (0.7)
D0 ltpTgt 1.3 GeV/c D?e ltpTgt 0.5 GeV/c
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Null Effect at RHIC?

• Null Effect of energy loss in AuAu?
• What is missing in this comparison? Reference pp
  data!

PLB 557 (2003) PLB 560 (2003)
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Electron Spectra
STAR PRL 94(2005) PHENIX AuAu PRL 88
(2002) PRL 94 (2005) PHENIX pp (QM04) S.
Kelly et al. 30(2004) S1189
Energy dependence Large dispersion of
data STAR/PHENIX pp, dAu, AuAu
(STAR) DNP03, QM04, ISMD04
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RAA and v2(D-gte)
PHENIX nucl-ex/0502009 F. Laue (STAR) SQM04
(PHENIX) ICPAQGP05
Collision (over radiation) energy loss? Low pT
(scc) binary scaling?
Need more statistics and lower syst. And
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Where is Beauty?
Need precise vertex detector able to measure B
decays
STAR Preliminary
A. Tai, A. Suide (STAR) QM04
hep-ph/0502203
QM05 STAR electron, direct charm in AuAu Will
the same puzzle continue?
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Centrality Dependence
Total Cross Section matches with hadron yield
(pTgt1.5 GeV/c)?Inclusive hadron yield due to
FSI Will strong centrality dependence of charm
spectral shape affect how we extract charm yield
from electron spectra? Direct charm at low pT in
AuAu
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Electrons at 62.4 GeV AuAu
Electron identification at 62.4GeV AuAu from
run4 Gamma conversion studied in details by
reconstructing ee- pairs at low invariant mass
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Photonic background
Photonic background matches with inclusive
electrons. ? Consistent with low charm yield at
62.4 GeV Ready for run4 AuAu electron spectra
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Conclusions

• Charged hadron identification at high pT can be
  done with STAR TPC (TOF)
• AuAu 62.4 GeV
• h/p ratios depend on charge, centrality and pT
• RCP of h and pions approach each at pT5 GeV/c
• AuAu 200 GeV
• Identification at high pT possible, p/h ratios
  decrease at pTgt3 GeV/c
• Rapidity Asymmetry of pions in dAu follows
  closely that of inclusive hadrons
• More and exciting results from high pT PID soon.
• Charm cross sections measured in pp, dAu and
  AuAu(soon).
• Comparisons to Models and other experiments
  discussed
• Open Charm measurements at RHIC exciting, but
  also have limitations/puzzles so far.
• Vertex detector upgrades needed!

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Low-mass ee- Pairs Prospects at RHIC
Need open charm suppression by 5 or measured
with -10
R. Rapp nucl-th/0204003
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Pamir EM shower depth
With charm
XREC upgrade
Without charm
Pamir, Nuovo Cim 24c (2001) 557
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STAR/PHENIX ? x2?
dN/dy (phi) JG MA STAR 6.5, PHENIX 3.9
Combined 6.0-0.4
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Charm From STAR
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Open Charm Spectrum
D/D0 ratio is consistent with other experiments
and models
A. Tai QM04
Power-law describes the spectrum well up to
11GeV/c Spectrum is very hard
STAR Preliminary
Different Measurements at different pT
bins. Study the limits on other pT bins?
Fantastic!!! But