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Measurements of Light Vector Mesons through the e + e - Channel at the PHENIX

Measurements of Light Vector Mesons through the e + e - Channel at the PHENIX. Xinhua Li for the PHENIX Collaboration University of California – Riverside. Introduction.

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Measurements of Light Vector Mesons through the e + e - Channel at the PHENIX

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  1. Measurements of Light Vector Mesons through the e+e- Channel at the PHENIX Xinhua Li for the PHENIX Collaboration University of California – Riverside

  2. Introduction Main goal of the Relativistic Heavy Ion Program at RHIC is detection of signals from potential phase transition in strongly interacting matter associated with deconfinement or chiral symmetry restoration Medium modifications of the light vector mesons should encode information on chiral restoration Decay to di-electrons is particularly interesting, since electrons do not re-scatter in the medium and their invariant mass reflects the mass of the vector meson in the altered vacuum state.

  3. Broadening ofr, w, f at high T Ralf Rapp, Physical Review C, 63 (2001)054907

  4. Central arms of the PHENIX Spectrometer Drift Chamber measures particle momentum Ring Imaging Cherenkov detects electrons Electro Calorimeter measures particle energy

  5. Electrons in PHENIX photon converter runs Number of photo- electrons in RICH Mass of e+e- pair E/p Chi2 in RICH

  6. RHIC Au-Au Luminosity

  7. Challenge 1) Small cross section Br(f->e+e- )dN/dy ~ 10-4; 2) Search for rare events in the environment of high multiplicity; 3) Large combinatorial background from photon conversions and Dalitz decays.

  8. Strategy 1. Select electron candidates. 2. Require positron and electron to be from different PHENIX central arms. 3. Transverse momentum above 300 MeV/c. 4. Reject electrons created from photon conversion. 5. Generate combinatorial background, using event mixing technique. 6. Normalize the background by , where is the number of e+e+ pairs from same events, is the number of e-e- pairs from same events, is the number of e+e- pairs from mixed events. 7. Subtract the background.

  9. Reconstructed f meson Statistics: 25.8 million minimum bias events of 200 AGeV AuAu Number of reconstructed f’s:

  10. Simulation

  11. Preliminary results , where is the number of f‘s corrected by embedding efficiency

  12. Outlook • In the next RHIC physics run: • Higher luminosity. • PHENIX Transition Radiation Detector will further improve electron identification. • EMCal-RICH electron trigger.

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