1. Jia Shen Saint Mary’s College of California Dr. Ralf Rapp Cyclotron Institute at Texas A&M University Dilepton Spectra from Open Charm Decays in Heavy-Ion Collisions

2. Quark-Gluon Plasma and Heavy-Ion Collisions A quark-gluon plasma is believed to exist during the first 10 microseconds after the universe is created from the Big Bang. In the heavy-ion collision, a quark-gluon plasma is believed to exist for a very short time. rhic.physics.wayne.edu/~sean/collision_a.gif

3. http://en.wikipedia.org/wiki/Quark-gluon_plasma Particles produced in a Heavy-Ion Collision as seen by the STAR Detector

4. This project How to detect the Quark-Gluon Plasma? Idea: - Light quarks and gluons thermalize quickly and lose imprinted information - charm quarks are much heavier and do not easily thermalize => more sensitive probe of interactions in QGP - use di-electron decay spectra from charm quarks to probe Quark-Gluon Plasma

5. Dilepton Spectra from PHENIX Collaboration (2007) Dileptons from charm dominant in the M=1-3GeV mass region!

6. Step-1: Angular Correlation between charm and anticharm quark Back-to-Back (no interaction) Random angle (thermalization)

7. Step-2: Input charm transverse-momentum spectra dN/dPt =c Pt e^(-Et/Teff) key parameter: Teff => slope of the charm spectrum

8. Step-3: Procedure to calculate e+e- spectrum Decay c-quark into positron in its rest system boost positron into lab system repeat for anticharm -> electron Calculate invariant mass of electron- positron pair: M^2=(E_+E+)^2-(P_+P+)^2 study dependence of invariant mass distribution on charm-quark input (slope and angular correlation)

9. Result-1: Sensitivity to charm-anticharm relative angle random angle gives softer spectrum than “back-to-back “(180deg)

10. Result-2: Sensitivity to slope of charm spectrum Back-to-back Random Angle softer charm pt-spectrum reflects itself in softer dilepton invariant-mass spectrum for both angular scenarios

11. Conclusions Sensitivity of dilepton spectra to single- charm and charm-anticharm correlations confirmed and quantified Experimental acceptance cuts implemented

12. Future Directions: More realistic charm-anticharm input spectra: Check against single electron spectra in p-p collisions Use a model for charm-quark Interactions in the QGP (consistent with single-electron spectra in Au-Au Collisions) to obtain charm and dilepton spectra in Au-Au collisions