Dielectrons and Direct Virutal Photons at RHIC-STAR
Shandong University, Qingdao, China 266237
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Published online: 16 June 2020
Electromagnetic probes are unique probes of the hot and dense medium cre- ated in relativistic heavy-ion collisions due to their minimal interactions with the partonic and hadronic medium. They can be produced at all stages of a collision, thus they provide unique ways to study the medium properties of the whole collision evolution. We present the dielectron invariant mass spectrum at √sNN = 27, 39, 39, and 62.4 GeV. Comparing to hadronic cocktail simulation, significant excesses of dielectron invariant mass spectrum at low mass are observed. The direct virtual photon invariant yields derived from the low-mass e+e− continuum in Au+Au collisions at √sNN = 200 GeV is presented and the excesses from thermal photons in low transverse momentum (pT) have been observed. Model calculations can simultaneously describe both dielectron low mass excesses and direct virtual photon low pT excesses.
© The Authors, published by EDP Sciences, 2020
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