论文标题
低$ p_t $直接光子生产用phenix测量
Low $p_T$ direct photon production at RHIC measured with PHENIX
论文作者
论文摘要
Phenix使用RHIC的多功能性将低$ p_ {t} $直接光子产生作为碰撞系统大小和梁能量的功能。对于大小对应于$ dn_ {ch}/dη$大于20-30的系统，我们观察到很大的直接光子产量，相对于反应平面的大型方位型各向异性以及$dn_γ/dy \ propto的特征性集中依赖性（dn_ propto） \\在此程序中，我们将在$ \ sqrt {s_ {nn}} $ = 39、62.4和200 GEV中呈现Au+Au碰撞的新结果。减去提示光子组件后，$ p_ {t} $的逆坡度从1-2 Gev/$ c $为250 meV/$ c $，但增加到2至4 gev/$ c $的范围约为400 meV/$ c $。在实验不确定性中，没有迹象表明逆斜率的系统尺寸依赖性。此外，通过功率$α$表示的收益率的系统大小依赖性在整个观察到的范围从1到6 GEV/$ C $中保持独立于$ p_ {t} $。像大产率和方位角各向异性一样，这些特征却与夸克gluon等离子体的热光子发射一致，但通过理论模型计算避免了定量描述。
PHENIX has used the versatility of RHIC to map out low $p_{T}$ direct photon production as function of collision system size and beam energy. For systems with a size corresponding to a $dN_{ch}/dη$ larger than 20-30, we observe a large yield of direct photons, a large azimuthal anisotropy with respect to the reaction plane, and a characteristic centrality dependence of $dN_γ/dy \propto (dN_{ch}/dη)^α$, with $α\sim$ 1.2. \\ In this proceeding, we will present new results from Au+Au collisions at $\sqrt{s_{NN}}$ = 39, 62.4 and 200 GeV. After subtracting the prompt photon component, the inverse slope for the $p_{T}$ range from 1-2 GeV/$c$ is 250 MeV/$c$, but increases to about 400 MeV/$c$ for the range from 2 to 4 GeV/$c$. Within the experimental uncertainty, there is no indication of a system size dependence of the inverse slope. Furthermore, the system size dependence of the yield, expressed through the power $α$, remains independent of $p_{T}$ over the entire observed range from 1 to 6 GeV/$c$. Like the large yield and azimuthal anisotropy, these features, while qualitatively consistent with the emission of thermal photons from the quark gluon plasma, elude a quantitative description through theoretical model calculations.
