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Open Charm Production at .

Open Charm Production at. Andrew Glenn University of Tennessee. July 7, 2004. Outline. Motivation (Experimental and Theoretical) Single muon Au+Au analysis Other charm data at PHENIX and STAR Summary and Outlook. Why is Charm Interesting (in A+A)?. Thermal. Pre-thermal.

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Open Charm Production at .

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  1. Open Charm Productionat . Andrew Glenn University of Tennessee July 7, 2004

  2. Outline • Motivation (Experimental and Theoretical) • Single muon Au+Au analysis • Other charm data at PHENIX and STAR • Summary and Outlook Andrew Glenn

  3. Why is Charm Interesting (in A+A)? Thermal Pre-thermal Initial production Hadronic QGP Can charm help show the difference? Vs. Andrew Glenn

  4. Charm Production Charm production at RHIC is dominated by gluon fusion Factorization theorem for charmed hadron production J.C.Collins,D.E.Soper and G.Sterman, Nucl. Phys. B263, 37(1986) ds [A+BH+X] = Sijfi/A fj/Bds [ijcc+X]DcH + ... fi/A, fj/B : distribution fuction for parton i,j DcH : fragmentation function for c ds [ijcc+X] : parton cross section + ... : higher twist (power suppressed by LQCD/mc, or LQCD/pt if pt≫mc ) : e.g. "recombination" PRL, 89 122002 (2002) Andrew Glenn B. L. Combridge et al. Nuc. Phys., B151:429–456, 1979

  5. Measure Thermalization Time? Initial estimates showed pre-equilibrium charm production to be similar to the initial production in a QGP at RHIC energy. Andrew Glenn Berndt Muller and Xin-Nian Wang. Phys. Rev. Lett., 68:2437–2439, 1992.

  6. Probably not. Refined estimates showed the post initial production to be small. Zi-wei Lin and M. Gyulassy. Nucl. Phys., A590:495c–498c, 1995. Peter L´evai, Berndt Muller, and Xin-Nian Wang. Phys. Rev., C51:3326–3335, 1995. Most charm is made via gluon fusion in the initial stage. Andrew Glenn

  7. Charm Enhancement? One early interpretation of the NA45 electron pair enhancement was a large charm enhancement P. Braun-Munzinger, D. Miskowiec, A. Drees, and C. Lourenco. Eur. Phys. J., C1:123–130, 1998. Andrew Glenn

  8. Quite Possibly (but less) Open CharmEnhancement ? NA50 Muon pair data showed that charm was not so largely enhanced. BUT there was still a significant excess which may be due to charm enhacement M. C. Abreu et al. Eur. Phys. J., C14:443–455, 2000. Andrew Glenn

  9. Centrality Dependence NA50 Enhancement up to 3.5 in central Pb+Pb M. C. Abreu et al. Eur. Phys. J., C14:443–455, 2000. Andrew Glenn

  10. Hadronization Fragmentation Vs. Coalescence Quarks can combine with unrelated fragmenting parton: ph = z p, z<1 Quarks can combine with unrelated quarks. Observed since ’77 as ‘leading particle effect’ (recombination). How much larger of a role might this play at RHIC; especially in a ‘quark soup’ (coalescence). recombining partons: p1+p2=ph Andrew Glenn

  11. Enhancement at RHIC Vs. SPS This region can’t contributeto open charm throughfragmentation. Maximum Enhancement Estimates show that RHIC will has a lower fraction of c quark pairs below 2mD threshold to contribute to enhancement via coalescence. Andrew Glenn A. P. Kostyuk, M. I. Gorenstein, and W. Greiner. Phys. Lett., B519:207–211, 2001.

  12. D Ratios • The ratios of different D mesons will differ in hadron vs. QGP scenario. • Free relativistic fermion quark gas at T=200 MeV and a baryon chemical potential, µ = 0: D−s / D− = 0.94 • A equilibrated hadronic bose gas at T=180 MeV: D−s / D− = 0.610 • Final state interactions such as D± + K± → D±s+ π± could modify the ratios and need to be corrected for. Cheuk-YinWong. Nucl. Phys., A630:487–498, 1998. and private communication Andrew Glenn

  13. Other Information from Charm Electrons from charm V. Greco, C. M. Ko, and R. Rapp. Quark coalescence for charmed mesons in ultrarelativistic heavy-ion collisions. 2003. Transverse momentum spectra and flow parameters are sensitive to QGP. Andrew Glenn

  14. Nuclear Effects Shadowing Nuclear effects such as shadowing, energy loss, kT broadening, cronin enhancement, and gluon saturation (Color Glass) need to be considered CGC Cronin Jens Ole Schmitt et al. Phys.Lett., B498:163–168, 2001. R. Vogt. Int. J. Mod. Phys., E12:211–270, 2003. Andrew Glenn B. Z. Kopeliovich, J. Nemchik, A. Schafer, and A. V. Tarasov. Phys. Rev. Lett., 88:232303, 2002. Dmitri Kharzeev and Kirill Tuchin. hep-ph/0310358, 2003.

  15. Charmonium Reference In the past, J/ψ production (supression) has been measured relative to Drell-Yan. In order to minimize nuclear effects, such as gluon shadowing, open charm will be a better reference. J/Psi to DY Charmonium has a much different production mechanism than Drell-Yan. J/Psi to Open Charm RHIC SPS/AGS H. Satz and K. Sridhar. Phys. Rev., D50:3557–3559, 1994. Andrew Glenn

  16. The Apparatus Steel Absorber Detector (Iarocci Tubes) Andrew Glenn

  17. Run II Au+Au Data Sample • RHIC Run II Au+Au (The first muon capable run) • Start With 7.7M Minimum-Bias Events(Cleanest section of running period) • Cuts on: • Vertex (-20 to 38cm) • Track Quality (2/DOF < 7, NTrHits >=12) •  (-1.51 to -1.79 or  = 155 -161o) Uniform acceptance in event vertex. • Azimuthal Cut Andrew Glenn

  18. Run IV Au+Au • Better Shielding (Tunnel and MuID Hole) • Better Statistics (~1.5 Billion Min-bias!) • Better Hardware Acceptance (stable HV..) Run II Run III Andrew Glenn

  19. Sources of Muon Candidates • D (B) meson semi-leptonic decays(D K …) Prompt Signal • Decay muons from hadron decays (±± , K±± ) • ‘Hadron’ Punch Through(±, K±, p) • Decays from J/, , Drell-Yan…(Small Contribution) MuID Gap 0 1 2 3 4 Background     Steel absorber Andrew Glenn

  20. Muon Identification MuID Last Gap = 2 Gap (Plain) 0 1 2 3 4 Centrality > 20% Data –Red Simulation –Black 1 GeV  Sharp Muon Peak 3 GeV  3 GeV  Long tail from interacting hadrons (more evidence to come) steel Main muon identification is from momentum/depth matching Andrew Glenn

  21. Run IV Stopping Peaks Muon Peaks South North Andrew Glenn

  22. Decay Contribution We want to separate the contribution from prompt muon production and /K decays • D c = 0.03 cm Decays before absorber •  c = 780 cm Most are absorbed, but some decay first • K c = 371 cm Most are absorbed, but some decay first • γcτ >> 80cm → Decay Probability nearly constant between nosecones magnet 40 cm X Muon tracker Muon ID Collision Point Z nosecone • Collisions occurring closer to the absorber will have fewer decay contributions. Should see a linear increase in decay background with increasing vertex. Andrew Glenn

  23. Vertex Dependence Very Linear Shape Due to Decays Centrality > 20% = Centrality > 20% 1 < pT > 3 GeV/c Centrality > 20% Not due to vertex detector resolution Andrew Glenn

  24. Interacting Hadron Vertex Last Gap = 2 Centrality > 20% Centrality > 20% Interacting Hadrons: Last Gaps 2 and 3, Pz St3 tail. Flat shape indicates little to no decay (hence muon) component Andrew Glenn

  25. Free Decay pT Distribution Muon Vertex Region I Region II Region II – Region I Centrality > 20% Decays Z absorber Scaled prompt decay + punchthrough + ?? Z vertex From simple (event vertex corrected) subtraction of near muons from far muons(Hence NOT NORMALIZED, also NOT ACCEPTANCE/EFFICIENCY CORRECTED) Andrew Glenn

  26. Simulations • With the availability of BRAHMS  and K data at Muon Arm rapidities, we can examine a data driven simulation approach. • An accurate modeling of K and  (and p) production for simulation input is required for punchthrough estimations. Andrew Glenn

  27. Data Driven Particle Generator BRAHMS5% most central 5% Most Central Events Provides scaling BRAHMS data extracted from Djamel Ouerdane’s thesis Use scaled PHENIX central arm data to for basis of event generator. BRAHMS preliminary data helps with scaling and justification ( P(y,pT) ≈ P(y)P(pT) ). Only measurements for 5% most central events are available from BRAHMS. Andrew Glenn

  28. Early Simulation Results • 900K Single K’s and ’s thrown with BRAHMS (preliminary, 5% most central) pT and dN/dy shapes. pT > 1 GeV required. Passed through full simulation/reconstruction. Decays Punchthrough (non-muons) Last Gap = 4Same  cut as data Last Gap = 4Same  cut as data Andrew Glenn Projected decay contribution ends at ~-73cm

  29. Rough Component Breakdown Free Decays z=-40cm nose cone Other Decays Z=-73cm decay sim. Punch Through Prompt muons + unresolved background (combinatoric …) Andrew Glenn

  30. Completing the Analysis • Complete large statistics simulations to more accurately estimate punch though and background. • Complete a more accurate estimate of combinatory background. • Bin analysis in pT to determine prompt muon spectra. • Finish acceptance*efficiency corrections. Andrew Glenn

  31. p+p Muon Open Charm Blueline = statistical uncertainty. Green band = systematic uncertainty. Prompt muons Blue dotted line = expectation. Measured decay muons with the expectation μ- No absolute value yet; final efforts in progress Y. Kwon et. al Andrew Glenn

  32. p+p Muon Open Charm II Max BG Work in progressestimates for backgroundsas a function of pT Min BG Y. Kwon et. al Andrew Glenn

  33. Has J/ψ Muon Data Andrew Glenn

  34. J/ψ Visible in Run IV Au+Au Data South Arm Centrality >40 Andrew Glenn

  35. Electron Measurements PHENIX PRELIMINARY Au+Au consistant with binary scaling p+p Andrew Glenn

  36. . Electron Measurements II Min. bias at Au+Au sNN=200GeV • Fully corrected spectrum • Acceptance & eID efficiencies • 2.5M and 2.2M events analyzed with and without the converter • Backgrounds from KeX (less than 5%) and , , ee (1%) decays subtracted • Systematic error is 13% at high pT (e++e–)/2 sys. error PHENIX Andrew Glenn

  37. 0 < pT < 3 GeV/c, |y| < 1.0 D± d+Au minbias D0+D0 7.4<pt<9.3 GeV/c STAR has measured charm in d+Au Mass plots from dAu data using event-mixing technique QM 2004 8.5< pt<11.0 GeV/c STAR also has a single electron charm measurement. Andrew Glenn

  38. Summary and Outlook • Open (and hidden) charm measurements are very important to RHIC HI/QGP physics. • PHENIX is capable of making charm measurements via semileptonic decays (at forward and central rapidity). • Electron measurments exhist, and muon measurements are close. • Quicker simulations (using staged cloning) are being tested to aid in estimating punch through. • Future upgrades may enhance our ability to do these measurements. (displaced vertex detection, pad chambers …) Andrew Glenn

  39. Additional Slides Andrew Glenn

  40. Peripheral Data Vs Simulation Simulation: Muons From Central Hijing Data: Centrality > 60 (For cleaner events) Last Gap = 2 Falsely extended tracks Last Gap = 4 No clear peak or tailsince last gap. Last Gap = 3 Andrew Glenn

  41. Hadronization Animations U C C U C U Andrew Glenn

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