Detailed measurement of the e+e- pair continuum in p plus p and Au plus Au collisions at √sNN=200 GeV and implications for direct photon production
Detailed measurement of the e+e- pair continuum in p plus p and Au plus Au collisions at √sNN=200 GeV and implications for direct photon production
复制标题
DOI：
10.1103/physrevc.81.034911
复制
发表时间：
2010-03-01
影响因子：
3.1
通讯作者：
Zolin, L.
中科院分区：
文献类型：
--
作者：
Adare, A.;Afanasiev, S.;Zolin, L.
PHENIX测量了根s（NN）= 200 GeV Au+Au和p+p碰撞中在宽质量和横动量范围内的e（+）e（-）对连续谱。e（+）e（-）产额与基于PHENIX测量的强子源的期望值进行了比较。在中质量区域，介于phi和J/psi介子的质量之间，产额与相关c（c）相对于棒产生的预期一致，尽管不排除其他机制。在低质量区，低于φ，p+p包含的质谱是很好地描述了已知的贡献轻介子衰变。相比之下，在该区域中的Au+Au最小偏差包含质谱显示出4.7 +/- 0.4（stat）+/- 1.5（syst）+/- 0.9（model）的因子增强。在低质量（m（ee）< 0.3 GeV/c（2））和高p（T）（1 < p（T）< 5 GeV/c）下，观察到增强的e（+）e（-）对产额，这与虚直接光子的产生一致。该过量被用于推断真实的直接光子的产额。在中心Au+Au碰撞中，直接光子产额超过p+p的部分在p（T）中是指数的，其反斜率T = 221 +/-19（stat）+/- 19（syst）MeV。流体动力学模型的初始温度范围从T-init类似或等于300-600 MeV的时间为0.6-0.15 fm/c的碰撞后，在定性协议与直接光子数据在Au+Au。当p（T）< 1 GeV/c时，低质量区的辐射会进一步增强，并随着中心性的增加而增加，而且T的斜率与100 MeV相似或相等。理论模型低估了低质量，低p（T）增强。
PHENIX has measured the e(+)e(-) pair continuum in root s(NN) = 200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. The e(+)e(-) yield is compared to the expectations from hadronic sources, based on PHENIX measurements. In the intermediate-mass region, between the masses of the phi and the J/psi meson, the yield is consistent with expectations from correlated c (c) over bar production, although other mechanisms are not ruled out. In the low-mass region, below the phi, the p+p inclusive mass spectrum is well described by known contributions from light meson decays. In contrast, the Au+Au minimum bias inclusive mass spectrum in this region shows an enhancement by a factor of 4.7 +/- 0.4(stat) +/- 1.5(syst) +/- 0.9(model). At low mass (m(ee) < 0.3 GeV/c(2)) and high p(T) (1 < p(T) < 5 GeV/c) an enhanced e(+)e(-) pair yield is observed that is consistent with production of virtual direct photons. This excess is used to infer the yield of real direct photons. In central Au+Au collisions, the excess of the direct photon yield over the p+p is exponential in p(T), with inverse slope T = 221 +/- 19(stat) +/- 19(syst) MeV. Hydrodynamical models with initial temperatures ranging from T-init similar or equal to 300-600 MeV at times of 0.6-0.15 fm/c after the collision are in qualitative agreement with the direct photon data in Au+Au. For low p(T) < 1 GeV/c the low-mass region shows a further significant enhancement that increases with centrality and has an inverse slope of T similar or equal to 100 MeV. Theoretical models underpredict the low-mass, low-p(T) enhancement.