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Dielectron production in Au + Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV

$$sqrt{s_{NN}}$$=200GeVでの金-金衝突における電子-陽電子対生成

Adare, A.*; 長谷川 勝一   ; 今井 憲一; 永宮 正治; 佐甲 博之   ; 佐藤 進  ; 谷田 聖   ; PHENIX Collaboration*; 他440名*

Adare, A.*; Hasegawa, Shoichi; Imai, Kenichi; Nagamiya, Shoji; Sako, Hiroyuki; Sato, Susumu; Tanida, Kiyoshi; PHENIX Collaboration*; 440 of others*

We present measurements of $$e^+e^-$$ production at midrapidity in Au + Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV. The invariant yield is studied within the PHENIX detector acceptance over a wide range of mass ($$m_{ee} < 5$$ GeV/$$c^2$$) and pair transverse momentum ($$p_T<5$$ GeV/$$c$$) for minimum bias and for five centrality classes. The $$e^+e^-$$ yield is compared to the expectations from known sources. In the low-mass region ($$m_{ee}=$$0.30-0.76 GeV/$$c^2$$) there is an enhancement that increases with centrality and is distributed over the entire pair $$p_T$$ range measured. It is significantly smaller than previously reported by the PHENIX experiment and amounts to $$2.3 pm 0.4({rm stat}) pm 0.4({rm syst}) pm 0.2({rm model})$$ or to $$1.7 pm 0.3({rm stat}) pm 0.3({rm syst}) pm 0.2({rm model})$$ for minimum bias collisions when the open heavy-flavor contribution is calculated with pythia or mc@nlo, respectively. The inclusive mass and $$p_T$$ distributions, as well as the centrality dependence, are well reproduced by model calculations where the enhancement mainly originates from the melting of the $$rho$$ meson resonance as the system approaches chiral symmetry restoration. In the intermediate-mass region ($$m_{ee}=$$1.2-2.8 GeV/$$c^2$$), the data hint at a significant contribution in addition to the yield from the semileptonic decays of heavy-flavor mesons.

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パーセンタイル:95.06

分野:Physics, Nuclear

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