Abstract
We report on measurements of dielectron production in collisions at a center-of-mass energy of 200 GeV per nucleon-nucleon pair using the STAR detector at BNL Relativistic Heavy Ion Collider. Systematic measurements of the dielectron yield as a function of transverse momentum and collision centrality show an enhancement compared to a cocktail simulation of hadronic sources in the low invariant-mass region . This enhancement cannot be reproduced by the -meson vacuum spectral function. In minimum-bias collisions, in the invariant-mass range of , integrated over the full acceptance, the enhancement factor is . The enhancement factor exhibits weak centrality and dependence in STAR's accessible kinematic regions, while the excess yield in this invariant-mass region as a function of the number of participating nucleons follows a power-law shape with a power of . Models that assume an in-medium broadening of the -meson spectral function consistently describe the observed excess in these measurements. Additionally, we report on measurements of - and -meson production through their decay channel. These measurements show good agreement with Tsallis blast-wave model predictions, as well as, in the case of the meson, results through its decay channel. In the intermediate invariant-mass region , we investigate the spectral shapes from different collision centralities. Physics implications for possible in-medium modification of charmed hadron production and other physics sources are discussed.
42 More- Received 9 April 2015
DOI:https://doi.org/10.1103/PhysRevC.92.024912
©2015 American Physical Society