Measurements of dielectron production in Au plus Au collisions at √sNN=27, 39, and 62.4 GeV from the STAR experiment

Authors：Abdulhamid, M. I.; Aboona, B. E.; Adam, J.; Adamczyk, L.; Adams, J. R.; Aggarwal, I.; Aggarwal, M. M.; Ahammed, Z.; Anderson, D. M.; Aschenauer, E. C.; Aslam, S.; Atchison, J.; Bairathi, V.; Baker, W.; Cap, J. G. Ball; Barish, K.; Bellwied, R.; Bhagat, P.; Bhasin, A.; Bhatta, S.; Bielcik, J.; Bielcikova, J.; Brandenburg, J. D.; Butterworth, J.; Cai, X. Z.; Caines, H.; Sanchez, M. Calderon de la Barca; Cebra, D.; Ceska, J.; Chakaberia, I.; Chaloupka, P.; Chan, B. K.; Chang, Z.; Chatterjee, A.

Source：Physical Review C - Nuclear Physics, 2023, 107(6): L061901.

DOI：10.1103/PhysRevC.107.L061901

• THERMAL DILEPTONS
• ENERGY-DEPENDENCE

We report systematic measurements of dielectron (e+e-) invariant-mass Mee spectra at midrapidity in Au + Au collisions at & RADIC;sNN = 27, 39, and 62.4 GeV taken with the STAR detector at the Relativistic Heavy Ion Collider. For all energies studied, a significant excess yield of dielectrons is observed in the low-mass region (0.40 < Mee < 0.75 MeV/c2) compared to hadronic cocktail simulations at freeze-out. Models that include an in-medium broadening of the p-meson spectral function consistently describe the observed excess. In addition, we report acceptance-corrected dielectron-excess spectra for Au + Au collisions at midrapidity (|yee| < 1) in the 0-80% centrality bin for each collision energy. The integrated excess yields for 0.4 < Mee < 0.75 GeV/c2, normalized by the charged particle multiplicity at midrapidity, are compared with previously published measure-& RADIC; ments for Au + Au at sNN = 19.6 and 200 GeV. Models that include an in-medium broadening of the p-meson spectral function consistently describe the observed excess. The normalized excess yields in the low-mass region show no significant collision energy dependence. The data, however, are consistent with model calculations that demonstrate a modest energy dependence.