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New Open Charm Results at STAR via Hadronic Decay Channels

New Open Charm Results at STAR via Hadronic Decay Channels. Stephen Baumgart Yale University For the STAR Collaboration. Outline. D 0 in 200 GeV Cu+Cu Collisions 1) Motivation 2) Previous Open Charm Results in STAR 3) Analysis Method 4) Charm Cross Section in Cu+Cu Collisions

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New Open Charm Results at STAR via Hadronic Decay Channels

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  1. New Open Charm Results at STAR via Hadronic Decay Channels Stephen Baumgart Yale University For the STAR Collaboration

  2. Outline • D0 in 200 GeV Cu+Cu Collisions • 1) Motivation • 2) Previous Open Charm Results in STAR • 3) Analysis Method • 4) Charm Cross Section in Cu+Cu Collisions • Ds in 200 GeV d+Au Collisions • 1) Motivation • 2) Results • Conclusions • Outlook

  3. Why Study Charm Production? • Prediction of Charm Cross Section in p+p from QCD (FONLL) • Deviations from prediction in Cu+Cu, Au+Au will show medium effects. Ref: M. Cacciari, P. Nason, R. Vogt, Phys. Rev. Lett. 95, 122001 (2005) • Charm production is a good probe of early state of medium • Charm produced during initial gluon fusion • Charm produced before thermalization. Ref: Kuznetsova, J. Rafelski Eur. Phys. J. C 51, 113-133(2007) Basic Gluon Fusion Diagram

  4. Previous D0 Results D0 measured via Kp channel in Au+Au, d+Au. pt spectra obtained, cross sections measured. D0 Peak Reconstructed from Kp in Au+Au, STAR Preliminary D0 Peak Reconstructed from Kp in d+Au,STAR Collaboration, J. Adams et al., Phys. Rev. Lett. 94, 062301 (2005).

  5. STAR Detector at RHIC The Relativistic Heavy Ion Collider The Relativistic Heavy Ion Collider (RHIC) is located at Brookhaven. RHIC uses p+p, d+A, and A+A beams. The STAR Detector The Solenoidal Tracker at RHIC (STAR) is one of four detectors. Data from the Time Projection Chamber (TPC) was used for this analysis.

  6. py px Analysis Method Kaon Tracks Pion Tracks Unused Tracks Combinatorial Technique Rotational Background Subtraction p Momentum and dE/dx cuts used K 5 degree rotations

  7. D0 + D0 in Cu+Cu STAR Preliminary Significance of peak = 4.7 s

  8. ( D0 + D0)/2Spectra in Cu+Cu STAR Preliminary Fitting Function: *Systematic error evaluation for dN/dy in progress.

  9. Conversion from dN/dy to Cross-Section number of binary collisions p+p inelastic cross section conversion to full rapidity ratio from e+e- collider data *Systematic error evaluation for dN/dy in progress.

  10. Charm Cross-Section Comparison at 200 GeV STAR d+Au (MinBias) STAR Au+Au (MinBias) STAR Cu+Cu (MinBias) STAR Preliminary FONLL upper limit PHENIX p+p (MinBias + g trigger) PHENIX Au+Au (MinBias) FONLL prediction FONLL lower limit *Systematic error evaluation for STAR Cu+Cu in progress.

  11. Studying the Ds Meson in RHI Collisions • Ds yields enhanced by deconfinement. • Ds production uses charm that might otherwise go into J/y production or other charmed mesons. • The strangeness/entropy ratio can be used to predict the D/Ds ratio . Ref: I. Kuznetsova, J. Rafelski “Charm and bottom flavored hadrons production from strangeness rich quark gluon plasma hadronization”. APS 2007 April Meeting Ref: I. Kuznetsova, J. Rafelski Eur. Phys. J. C 51, 113-133(2007)

  12. D/Ds Peak in d+Au STAR Preliminary *Mass difference fixed Ds+ D+ Ds+ Significance = 3.4 s D+ Significance = 2.4 s X Efficiency Corrections not done yet X Low statistics for D, not resilient to large changes in cuts X No negatively charged D or Ds found yet

  13. Conclusions • 4.7s D0 peak found in Cu+Cu Collisions • First D0 measurement in Cu+Cu at RHIC • Charm cross section in Cu+Cu measured to be 0.94 +/- 0.18 (stat.) mb • Consistent with Binary Scaling • 3.4s Ds+ peak found in d+Au Collisions • First Ds measurement in a heavy ion experiment

  14. Outlook • Need accounting of systematic errors for D0 in Cu+Cu • More Au+Au statistics will improve open charm measurements • Ds search in Au+Au planned • TOF & HFT upgrades to STAR will improve charm measurements

  15. References (Backup) [1] M. Cacciari, P. Nason, R. Vogt, Phys. Rev. Lett. 95, 122001 (2005) [2] I. Kuznetsova, J. Rafelski Eur. Phys. J. C 51, 113-133(2007) [3] I. Kuznetsova, J. Rafelski “Charm and bottom flavored hadrons production from strangeness rich quark gluon plasma hadronization”. APS 2007 April Meeting

  16. Pt Bins (Backup) 0.3 < pt < 1.3 GeV/c 1.3 < pt < 2.3 GeV/c STAR Preliminary STAR Preliminary 2.3 < pt < 3.3 GeV/c STAR Preliminary

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