arXiv 1704.030462017-04-13nucl-ex

用STAR测量p+p和Au+Au碰撞中的共享动量分数$z_g$

Measurement of the Shared Momentum Fraction $z_g$ using Jet Reconstruction in p+p and Au+Au Collisions with STAR

Kolja Kauder

备注：: Proceedings of Quark Matter 2017 (XXVI International Conference on Ultrarelativistic Heavy-ion collisions)
DOI：: 10.1016/j.nuclphysa.2017.07.004

摘要：

当前能量损失模型的一个关键区别在于Altarelli-Parisi，AP，分裂函数的处理。已经表明，由SoftDrop梳理过程确定的共享动量分数，此后称为射流分裂函数$z_g$，可以对p+p碰撞中的对称AP函数进行Sudakov安全测量。STAR合作提出了在p+p和Au+Au碰撞中在$\sqrt{s_{NN}}=200$ GeV处的第一个z_g测量，其中在Au+Au中，我们使用在我们以前的动量不平衡测量中引入的特定双喷流选择。对于喷流分辨率参数$R=0.4$，这些双喷流对被认为是显着不平衡的p+p，但恢复平衡时，所有软成分。我们发现，在不确定性内，没有任何迹象表明，修改后的喷射分裂功能的触发或反冲侧，这di-jet选择。

英文摘要：

One key difference in current energy loss models lies in the treatment of the Altarelli-Parisi, AP, splitting functions. It has been shown that the shared momentum fraction, henceforth called Jet Splitting Function $z_g$ as determined by the SoftDrop grooming process can be made a Sudakov-safe measurement of the symmetrized AP functions in p+p collisions. The STAR collaboration presents the first z_g measurements at $\sqrt{s_{NN}}=200$ GeV in p+p and Au+Au collisions, where in Au+Au we use the specific di-jet selection introduced in our previous momentum imbalance measurement. For a jet resolution parameter of $R=0.4$, these di-jet pairs were found to be significantly imbalanced with respect to p+p, yet regained balance when all soft constituents were included. We find that within uncertainties there are no signs of a modified Jet Splitting Function on trigger or recoil sides of this di-jet selection.

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