arXiv 0907.46022009-07nucl-ex

在RHIC-PHENIX对来自热和致密物质的软和中间$p_T$光子的测量

Measurements of soft and intermediate $p_T$ photons from hot and dense matter at RHIC-PHENIX

Yorito Yamaguchi

备注：: 4 pages, 3 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee
发表信息：: Nucl.Phys.A830:575c-578c,2009
DOI：: 10.1016/j.nuclphysa.2009.10.107

摘要：

在PHENIX用虚光子方法测量了$1.0 < p_{T} < 5.0 $ GeV/ $c$中p+p和Au+Au碰撞的直接光子。虚直接光子分量与包含的$e^{+}e^{-}$产率的分数通过使用$e^{+}e^{-}$质谱的形状分析来确定，所述$e^{+}e^{-}$质谱在$1.0 < p_{T} < 5.0 $ GeV/$c$的$m_{ee} < 300 $ MeV/$c^{2}$中。在p+p和Au+Au碰撞中的实际直接光子谱是从虚拟直接光子分数获得的，并且在Au+Au碰撞中看到了比二进制标度的p+p结果显著的过量。流体动力学模型再现了Au+Au的结果，表明物质的初始温度高于QGP的临界温度。2008年的d+Au数据由于其大量的统计数据而有望评估核效应的贡献。

英文摘要：

The measurements of direct photons in $1.0 < p_{T} < 5.0 $GeV/$c$ for p+p and Au+Au collisions have been made through the virtual photon method at PHENIX. The fraction of the virtual direct photon component to the inclusive $e^{+}e^{-}$ yield is determined by a shape analysis using the $e^{+}e^{-}$ mass spectra in $m_{ee} < 300 $MeV/$c^{2}$ for $1.0 < p_{T} < 5.0 $GeV/$c$. The real direct photon spectra in p+p and Au+Au collisions are obtained from the virtual direct photon fractions, and a significant excess over a binary-scaled p+p result is seen in Au+Au collisions. Hydrodynamical models which reproduce the Au+Au result indicate the initial temperature of the matter is higher than the critical temperature of QGP. The d+Au data taken in 2008 are promising to evaluate the contribution of the nuclear effects because of its large statistics.

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