In-medium modification of dilepton continuum at the PHENIX experiment at RHIC

by Alberica Toia (Stony Brook University, USA)

Friday 6 Jul 2007, 14:00 → 15:00 Europe/Zurich

IT AMPHITHEATRE (CERN)

Among other penetrating probes, electromagnetic probes are ideal tools to investigate the full time evolution and dynamics of the hot and dense matter produced in high energy heavy ion collisions, as they undergo no interaction in the final state. In the dilepton continuum Dalitz decays of light hadrons and direct decays of vector mesons, which might be modified in the medium, add to hard processes, such as correlated charm production and to direct thermal photons, emitted as a blackbody radiation from the plasma.

PHENIX is the only RHIC detector designed to reconstruct both electrons and muons, and thus to study dielectron, dimuon, but also electron-muon signals, therefore covering a large rapidity acceptance.

PHENIX has measured the dielectron continuum in heavy ion reactions at sqrt (s_NN)= 200 GeV and compared peripheral collisions, which agree well to the cocktail of known hadronic sources, with more central collisions, which show an indication of an enhanced yield in the low mass region. The intermediate mass region on the other hand hints at a suppression pattern increasing with centrality which adds additional information to the charm medium modifications.

First measurements of p+p reactions can provide a baseline to constrain the reference and interpret the signals in heavy ion collisions. Data from different measurements will be shown and compared to the superposition of meson decays and theoretical results on thermal radiation from pion annihilation in the hot fireball, including or not medium modifications of the intermediate rho meson.

http://aliceinfo.cern.ch/static/HIF/welcome.html