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Measurement of Open Heavy Flavor Production in STAR Experiment at RHIC

Measurement of Open Heavy Flavor Production in STAR Experiment at RHIC. W. Xie for STAR Collaboration (Purdue University, West Lafayette).  l. Motivation for Studying Heavy Quarks. Heavy quark mass are external parameter to QCD. Sensitive to initial gluon density and gluon distribution.

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Measurement of Open Heavy Flavor Production in STAR Experiment at RHIC

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  1. Measurement of Open Heavy Flavor Production in STAR Experiment at RHIC W. Xie for STAR Collaboration (Purdue University, West Lafayette) DIS2010 Convitto della Calza, Firenze, 19th - 23rd April 2010

  2. l Motivation for Studying Heavy Quarks • Heavy quark mass are external parameter to QCD. • Sensitive to initial gluon density and gluon distribution. • Interact with the medium differently from light quarks. • Suppression or enhancement pattern of heavy quarkonium production reveal critical features of the medium. • Cold Nuclear effect (CNM): • Different scaling properties in central and forward rapidity region CGC. • Gluon shadowing, etc K+ e-/- K- Non-photonic electron  D0 Open heavy flavor e-/- e+/+ Heavy quarkonia

  3. The STAR Detector MTD EMC barrel MRPC ToF barrel EMC End Cap FMS BBC FPD TPC FHC PMD Completed DAQ1000 HLT Ongoing R&D HFT FGT

  4. The Long Standing Issue on RHIC NPE Measurement STAR STAR d+Au PRL 94(2005)62301 PRL 97(2006)252002 PRL 94(2005)082301 • Results differ by a factor of two in • pT spectra • Total cross section • p+p collisions • Au+Au collisions • Investigation is underway STAR PRL 97(2007)192301 PHENIX PRL 98(2007)172301

  5. STAR Solution • Significantly Increase the S/B of this analysis (2008-present) • Cross check NPE measurements with early runs. γ conversion R STAR preliminary Beam pipe + SVT + SSD+ Dalitz Count Beam pipe + Dalitz TPC Inner Field cage Yield of conversion electrons at different radial location R(cm)

  6. STAR high pT NPE Measurements in 200GeV p+p collisions • Measurement done using TPC+EMC using run08 and run05 data. • pT>2.5GeV/c NPE measurement with dramatically different background agree with each very well • Combined using “Best Linear Unbiased Estimate”. χ2/ndf = 4.81/7 = 0.69

  7. Comparison with the Published NPE Results • STAR and PHENIX NPE result in 200GeV p+p collisions • Are consistent within errors at pt > 2.5 GeV/c • STAR High pT NPE results are consistent with FONLL in 200GeV p+p collisions

  8. Disentangle Charm and Bottom Production B • Wider φ distribution for B meson because of the larger mass. • Combined fit on data to obtain the B meson contribution to non-photonic electron. D hep-ph/0602067

  9. Disentangle Charm and Bottom Production STAR preliminary JPG35(2008)104117 JPG35(2008)104117 • Near side: mostly from B mesons • Away side: charm (~75%), Bottom (~25%)

  10. B Quark contribution is Significant in p+pcolliosions STAR preliminary Nuclear Physics A830 (2009)849c ~30-60% of non-photonic electron come from B meson decay in 200GeV p+p collisions.

  11. Constrain B quark Cross Section STAR preliminary Nuclear Physics A830 (2009)849c • Obtain B quark high pT spectrum • Constrain B quark Production Cross Section at RHIC using Model predictions.

  12. Future of Heavy Flavor Measurement at STAR MTD (MRPC)

  13. Summary and Perspective • STAR NPE results and PHENIX published result are consistent within errors at pt > 2.5 GeV/c in 200GeV p+p Collisions. • STAR hight pT NPE Results are consistent with FONLL. • New measurements of D mesons and low pT NPE using TOF should provide good constraints on total charm cross section • Expecting exciting results in the coming years with upgraded detectors and luminosity.

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  15. Future of Heavy Flavor Measurement at STAR MTD (MRPC) Courtesy of T. Ullirich

  16. Analysis Method in STAR for High pT NPE Dominant background: • Photonic Reconstruction Efficiency • estimated from embedding. • Small variation in ε can leads to large difference in NPE

  17. Combining run5 and run8 results Using “Best Linear Unbiased Estimate” NIM A500(2003)391, • χ2/ndf = 4.8/7 = 0.69 • Run05 and run08 are consistent with each other.

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