Measurements of dielectron production in Au + Au collisions at sNN =200 GeV from the STAR experiment
We report on measurements of dielectron (e+e-) production in Au+Au 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 (pT) and collision centrality show an enhancement compared to a cocktail simulation of hadronic sources in the low invariant-mass region (Mee<1GeV/c2). This enhancement cannot be reproduced by the ρ-meson vacuum spectral function. In minimum-bias collisions, in the invariant-mass range of 0.30-0.76GeV/c2, integrated over the full pT acceptance, the enhancement factor is 1.76±0.06(stat.)±0.26(sys.)±0.29(cocktail). The enhancement factor exhibits weak centrality and pT 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 1.44±0.10. Models that assume an in-medium broadening of the ρ-meson spectral function consistently describe the observed excess in these measurements. Additionally, we report on measurements of ω- and φ-meson production through their e+e- decay channel. These measurements show good agreement with Tsallis blast-wave model predictions, as well as, in the case of the φ meson, results through its K+K- decay channel. In the intermediate invariant-mass region (1.1<3GeV/c2), 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.
Adamczyk, L; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Alekseev, I; Alford, J; Aparin, A; Arkhipkin, D; Aschenauer, EC; Averichev, GS; Banerjee, A; Bellwied, R; Bhasin, A; Bhati, AK; Bhattarai, P; Bielcik, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Bouchet, J; Brandin, AV; Bunzarov, I; Burton, TP; Butterworth, J; Caines, H; Calderón De La Barca Sánchez, M; Campbell, JM; Cebra, D; Cervantes, MC; Chakaberia, I; Chaloupka, P; Chang, Z; Chattopadhyay, S; Chen, JH; Chen, X; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, HJ; Das, S; De Silva, LC; Debbe, RR; Dedovich, TG; Deng, J; Derevschikov, AA; Di Ruzza, B; Didenko, L; Dilks, C; Dong, X; Drachenberg, JL; Draper, JE; Du, CM; Dunkelberger, LE; Dunlop, JC; Efimov, LG; Engelage, J; Eppley, G; Esha, R; Evdokimov, O; Eyser, O; Fatemi, R; Fazio, S; Federic, P; Fedorisin, J; Feng, Z; Filip, P; Fisyak, Y; Flores, CE; Fulek, L; Gagliardi, CA; Garand, D; Geurts, F; Gibson, A; Girard, M; Greiner, L; Grosnick, D; Gunarathne, DS; Guo, Y; Gupta, S; Gupta, A; Guryn, W; Hamad, A; Hamed, A; Haque, R; Harris, JW; He, L; Heppelmann, S; Hirsch, A; Hoffmann, GW; Hofman, DJ; Horvat, S; Huang, B; Huang, X; Huang, HZ; Huck, P; Humanic, TJ; Igo, G
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