Dielectron production in Au plus Au collisions at root s(NN)=200 GeV

Adare, Andrew
Ogilvie, Craig
Apadula, Nicole
Campbell, Sarah
Ding, Lei
Dion, Alan
Hill, John
Hotvedt, Nels
Kempel, Todd
Lajoie, John
Lebedev, Alexandre
Ogilvie, Craig
Patel, Milap
Pei, H.
Perry, Joshua
Rinn, Timothy
Rosati, Marzia
Shimomura, M.
Silva, C.
Timilsina, Arbin
Wei, Feng
et al.
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We present measurements of e(+)e-production at midrapidity in Au + Au collisions at root 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 +/- 0.4(stat) +/- 0.4(syst) +/- 0.2(model) or to 1.7 +/- 0.3(stat) +/- 0.3(syst) +/- 0.2(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.

<p>This is an article from <em>Physical Review C </em>93 (2016): 014904, doi:<a href="http://dx.doi.org/10.1103/PhysRevC.93.014904" target="_blank">10.1103/PhysRevC.93.014904</a>. Posted with permission.</p>