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STAR Open Heavy Flavor Measurements

STAR Open Heavy Flavor Measurements. Gang Wang ( UCLA ). Motivation D 0 / D s / D* Non-photonic electron Summary. 1. X. Zhu, et al , Phys. Lett. B647 , 366(2007). Why heavy quarks?. - Higgs m ass: electro-weak symmetry breaking (current quark mass).

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STAR Open Heavy Flavor Measurements

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  1. STAR Open Heavy Flavor Measurements Gang Wang (UCLA) • Motivation • D0 / Ds / D* • Non-photonic electron • Summary 1

  2. X. Zhu, et al, Phys. Lett. B647, 366(2007). Why heavy quarks? - Higgs mass: electro-weak symmetry breaking (current quark mass). - QCD mass: Chiral symmetry breaking (constituent quark mass). • Strong interactions do not affect heavy-quark mass. • Initial fusion dominates heavy flavor production. • Study properties of the hot and dense medium at the early stage of heavy-ion collisions. • Light flavor thermalization. M. Gyulassy & Z. Lin, PRC 51 (1995) 2177 Charm quark

  3. Large acceptance |h| < 1, 0 < f < 2p • TPC dE/dx, momentum • TOF 1/b difference The STAR detector and Particle ID p K p Run9 ~ 72% of full TOF Run10: 100% significantly improved PID for final state hadrons, especially for kaons 3

  4. D0 PRL. 94 (2005) 62301 run3 Previous D0 measurements run4 STAR Preliminary ArXiv: 0805.0364

  5. run4 run3 NPE+μ NPE+D0 NPE+μ+D0 STAR Preliminary ArXiv: 0805.0364 Nbin scaling • Charm x-section ~ Nbin. Difficulties: • Short life time • Low production rate • Large combinatorial bg

  6. D0 in 200GeV p+p 0.4 < pT < 2.2 GeV/c Same sign Mixing event Track rotation run9 Yifei Zhang, DNP2010 talk Mass window: 1.72 – 2.1 GeV/c2 ~ 4s signal observed.

  7. Dsin 200GeV Au+Au with the help of Silicon Vertex Tracker. • Assume pT spectrum shape similar to D0: 47% yield covered. • D± yields estimated from D±/D0 ratio from e+e- data. run7 I.Kuznetsova, J. Rafelski, Eur. Phys. J. C 51 1 (2007) 113-133 Sarah LaPointe, WWND2010 talk Preliminary results indicate statistical hadronization.

  8. D*in 200GeV p+p run4 Background combinations: Wrong sign: D0 and -, D0bar and + Side band: 1.72< M(K) < 1.80 or 1.92 < M(K) < 2.0 GeV/c2 Yifei Zhang, DNP2010 talk All triggers included. More than 4s signal at low pT and very significant at high pT - mostly from EMC-based high neutral energy triggers.

  9. No significant charge asymmetry D*in 200GeV p+p STAR Preliminary All triggers included. More than 4s signal at low pT and very significant at high pT - mostly from EMC-based high neutral energy triggers. Wrong sign and side-band method reproduce background well. Yifei Zhang, DNP2010 talk 9

  10. Summary: D mesons • Previous STAR NPE/μ/D0 measurents in Au+Au and d+Au show the Nbin scaling of charm x-section. • STAR Dsmeasurement in Au+Au tends to support the statistical hadronization model. • Open charm hadrons are reconstructed from STAR run9 p+p 200 GeV data. • 4 sD0 signal at low pT and more significant D* signal at high pT are observed. • Working on efficiency for pT spectra and cross-section. 10

  11. Photon conversions p0 → g g, g→ e+ e- in material Dalitz decays p0 → ge+ e- Heavy flavor electrons D/B → e± + X Weak Kaon decays Ke3: K± → p0e±e < 3% contribution in pT > 1 GeV/c Vector Meson Decays w, , fJ,  → e+e- < 15% contribution in all pT Electron signal and background Non-photonic electron Photonic electron 11

  12. Long and slowly dying issue on RHIC NPE STAR STAR PRL 97(2007)192301 PHENIX PRL 98(2007)172301 run3 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 12

  13. STAR efforts STAR preliminary Beam pipe + SVT + SSD+ Dalitz • Significantly Increase the S/B of this analysis (2008-present) • Cross check NPE measurements with early runs. Count Beam pipe + Dalitz TPC Inner Field cage R(cm) Wei Xie, HP2010 talk 13 Yield of conversion electrons at different radial location

  14. STAR high pT NPE in 200GeV p+p Wei Xie, HP2010 talk • Measurement done using TPC+EMC using run08 and run05 data. • pT>2.5GeV/c NPE measurement with dramatically different background agree with each other very well • Combined using “Best Linear Unbiased Estimate”. χ2/ndf = 4.81/7 = 0.69 14

  15. Comparison with the Published NPE Results Wei Xie, HP2010 talk • STAR and PHENIX NPE result in 200GeV p+p collisions • consistent within errors at pT > 2.5 GeV/c • STAR High pT NPE results are consistent with FONLL in 200GeV p+p collisions 15 See Wenqin Xu's talk for details on eB x-section!

  16. Near Side: what’s the contribution of B/D decay to the non-photonic electrons? trigger Motivations Conical Pattern in 2-Particle Correlations in Au+Au Collisions pTtrig= 3-4.0 GeV/c; pTasso = 0.5-1 GeV/c What if we trigger on non-photonic electrons? Away Side in medium: How does B/D lose energy? Via conical emission? 16

  17. Study of heavy flavor via non-photonic electrons PYTHIA • Dmesons have their directions well represented by the daughter electrons, above 1.5 GeV/c. • Electrons from B decays can represent the B meson momentum direction well if pT > 3 GeV/c. 17

  18. 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

  19. B Meson Suppression in 200 GeV Au+Au Phys. Rev. Lett. 105 (2010) 202301 run5&6 • ~30-60% of non-photonic electron come from B meson in 200GeV p+p collisions. • Assume the same fraction in Au+Au collisions, results indicate B meson is suppressed See Andre Mischke's talk for details! 19

  20. NPE-h Correlation in 500 GeV p+p Wei Li (ATHIC2010 talk) run9 • Raw NPE-h correlation without pile-up removal in 500GeV p+p collisions. • PYTHIA simulation still shows different near-side peaks for NPE from D and B. 20

  21. Broadened Awayside in the NPE-h Correlations CuCu AuAu 34.4 / 5 21.7 / 5 B. Biritz (QM2009) run5 run7 0 – 20%: 3 < pTtrig< 6 GeV/c & 0.15 < pTasso< 0.5 GeV/c Away side broadened, beyond PYHTIA fit, in both the Au+Au and the Cu+Cu collisions 21

  22. Non-photonic e-h correlations in d+Au 200 GeV 3 < pTtrig< 6 GeV/c & 0.15 < pTasso< 0.5 GeV/c run8 The away-side correlation can be well described by PYTHIA calculations for p+p. No medium effects seen here. Gang Wang, HP2010 talk

  23. Motivations Partonic flow picture is supported for u, d, s. What about heavier quarks? PHENIX, arXiv:nucl-ex/0604011; STAR, Nucl. Phys. A 830(2009)19c. Above 1.5 GeV/c, D-decay electrons well represent the mother D mesons’ direction. eDv2 ~ D v2 Similarly, above 3 GeV/c, eBv2 ~ B v2

  24. NPEv2 run7 Non-photonic e v2 is lower than hadron v2 (or KS0, Λ). STAR, Phys. Rev. C 77 (2008) 54901 Gang Wang, HP2010 talk 24

  25. Discrepancy in high pT NPE has been solved! • NPE-h correlations have been measured in p+p collisions to retrieve B and D contributions, and used to study B energy loss. • Using d+Au as a reference, the shape of NPE-h correlation on the away-side is found to be modified in central Cu+Cu and Au+Au collisions due to the presence of the dense medium created in these collisions. • NPE v2 values obtained via fitting the correlations fall in a reasonable range, and are lower than hadron(or KS0, Λ) v2. • Correlations with heavy flavor tag: jet reconstruction, ridge.. Summary: NPE 25

  26. Future of Heavy Flavor Measurement at STAR MTD (MRPC) See Xin Dong's talk for details! 26

  27. backup 27

  28. 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%)

  29. K*in 200GeV p+p K*0 0.4 < pT < 2.2 GeV/c K2*(1430) Yifei Zhang, DNP2010 talk Run 9 p+p 200 GeV 105M minbias events Three different methods to reproduce combinatorial background. Very good K*0 and K2*(1430) signal observed.

  30. Energy loss mechanisms of non-photonic Electrons l l u u u l K+ K+ Hot/Dense Medium c quark e-/- c c light D0 D0 D0 meson energy loss Ivan, et al K+ Hot/Dense Medium “dead cone effect”: gluon radiation suppressed at q< mQ/EQ c quark e-/- c D0 radiative energy loss (D. kharzeev, M.Djordjevicet al. ) Hot/Dense Medium c quark e-/- collision energy loss (Teany, Ralf, Denes et al.) 30 Wei Xie, HP2010 talk

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