arXiv 1802.061112018-02-16hep-phnucl-th

中心偏置pA和pp碰撞中的小x胶子分布

The small-x gluon distribution in centrality biased pA and pp collisions

Adrian Dumitru, Gary Kapilevich, Vladimir Skokov

备注：: 14 pages, 5 figures
DOI：: 10.1016/j.nuclphysa.2018.03.012

摘要：

核修饰因子$R_{pA}(p_T)$提供了强子对撞机上原子核小$x$胶子分布的信息。最近的几个实验测量的核修改因子不仅在最小偏差，而且为中央$pA$碰撞。本文分析了通过硬粒子数的中心性选择对软胶子场组态的影响。这种偏向可以看作是小- $x$胶子组态的重新加权。我们发现，中心碰撞的偏置核修正因子${\cal Q}_{pA}(p_T)$高于最小偏置事件的$R_{pA}(p_T)$，并且即使在小的$x$下，它也可能重新形成“克罗宁峰”。如果能够选择更紧凑的抛射体质子构型，使胶子占据更小的横截面积$A_\perp$，则预计峰值的大小将近似地像$1/{A_{\perp}}^ν$、$ν\sim0.6\pm0.1$那样增加。我们预测一个增强的${\cal Q}_{pp}(p_T)-1 \sim 1/(p_T^2)^ν$和克罗宁峰，即使中央$pp$碰撞。

英文摘要：

The nuclear modification factor $R_{pA}(p_T)$ provides information on the small-$x$ gluon distribution of a nucleus at hadron colliders. Several experiments have recently measured the nuclear modification factor not only in minimum bias but also for central $pA$ collisions. In this paper we analyze the bias on the configurations of soft gluon fields introduced by a centrality selection via the number of hard particles. Such bias can be viewed as reweighting of configurations of small-$x$ gluons. We find that the biased nuclear modification factor ${\cal Q}_{pA}(p_T)$ for central collisions is above $R_{pA}(p_T)$ for minimum bias events, and that it may redevelop a "Cronin peak" even at small $x$. The magnitude of the peak is predicted to increase approximately like $1/{A_{\perp}}^ν$, $ν\sim0.6\pm0.1$, if one is able to select more compact configurations of the projectile proton where its gluons occupy a smaller transverse area $A_\perp$. We predict an enhanced ${\cal Q}_{pp}(p_T)-1 \sim 1/(p_T^2)^ν$ and a Cronin peak even for central $pp$ collisions.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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