27 September 2015 to 3 October 2015
Kobe, Fashion Mart, Japan
Japan timezone

System-size and energy dependences of dielectron excess invariant-mass spectra at STAR

30 Sept 2015, 11:10
20m
Exhibition Space 2-B

Exhibition Space 2-B

Contributed talk Electromagnetic Probes Electromagnetic Probes II

Speaker

Mr Shuai Yang (University of Science and Technology of China)

Description

Dilepton measurements play an essential role in the study of hot and dense nuclear matter, created in heavy-ion collisions. Dileptons are produced in the whole evolution of the system and escape with minimum interaction with the strongly interacting medium. Thus, they provide information about the various stages of the system during the evolution. In the low mass region ($M_{ee}<1.1$ $GeV/c^{2}$), they retain information about the in-medium modifications of vector mesons which are considered as a link to chiral symmetry restoration. Recently, it is found in a model calculation that the charged particle multiplicity normalized dilepton excess yield in the low mass region is proportional to the lifetime of the hot, dense medium created in heavy-ion collisions at $\sqrt{s_{NN}}$ = 6-200 $GeV$ [1]. The energy density created in U+U collisions at $\sqrt{s_{NN}}$ = 193 $GeV$ is expected to be higher by about 20% and the medium created might have a longer lifetime compared with the Au+Au collisions at $\sqrt{s_{NN}}$ = 200 $GeV$. Thus it would be interesting to compare the normalized dielectron excess yields in U+U and Au+Au collisions. In this talk, we will present the invariant mass, transverse momentum, and centrality dependent measurements of dielectron production in U+U collisions at $\sqrt{s_{NN}}$ = 193 $GeV$. With the acceptance correction applied, we will report the invariant dielectron excess mass spectra in U+U collisions at $\sqrt{s_{NN}}$ = 193 $GeV$ and in Au+Au at $\sqrt{s_{NN}}$ = 27, 39, and 62.4 $GeV$. Comparisons with the NA60 results and the STAR measurements in Au+Au collisions at $\sqrt{s_{NN}}$= 19.6 and 200 $GeV$ will be shown. System-size and energy dependences of low mass excess yield will be discussed together with model comparisons. [1] R. Rapp and H. van Hees, arXiv: 1411.4612.
On behalf of collaboration: STAR

Primary author

Mr Shuai Yang (University of Science and Technology of China)

Presentation materials