STAR中p+p和Au+Au碰撞的喷注子结构和部分子簇射演化
Jet sub-structure and parton shower evolution in p+p and Au+Au collisions at STAR
摘要：
最近在RHIC和LHC上对喷流结构变化的测量突出了差分测量对研究喷流淬灭性质的重要性。由于这些喷流结构的可观测量是密切依赖于部分子演化的角度和能量尺度，测量需要解开这两个尺度，以探测在不同的长度尺度的介质，研究其特性，如相干长度。为此，STAR合作提出了完全展开的射流子结构观测结果，旨在通过SoftDrop共享动量分数，梳理射流半径和200 GeV p+p碰撞中的射流质量作为射流横向动量的函数来提取与部分子簇射相关的基本量。我们还展示了第一次测量的迭代软滴梳理可观的第一，第二和第三分裂的起始叉横向动量范围从20-25 GeV。在比较未校正的数据，我们的模拟，我们能够看看快照的射流集群的历史，导致了解的时间演化的部分子簇射。建立了p+p基线，我们提出了第一次测量的射流的固有角结构在Au+Au碰撞在200 GeV通过实验鲁棒观测的两个领先的子射流（$θ_{SJ}$）之间的开口角。在金+金碰撞在星，我们利用一个特定的双射流选择在我们以前的动量不平衡（$A_{J}$）测量和测量的$A_{J}$和反冲射流光谱差异作为一个函数的角度类的基础上观察到的$θ_{SJ}$。通过这样的测量，我们探测介质对射流的响应，在特定的分辨率尺度上，并没有发现$θ_{SJ}$给出的不同角度尺度的射流在淬灭方面的显著差异。
英文摘要：
Recent measurements of jet structure modifications at RHIC and LHC highlight the importance of differential measurements to study the nature of jet quenching. Since these jet structure observables are intimately dependent on parton evolution in both the angular and energy scales, measurements are needed to disentangle these two scales in order to probe the medium at different length scales to study its characteristic properties such as the coherence length. To that effect, the STAR collaboration presents fully unfolded results of jet sub-structure observables designed to extract fundamental quantities related to the parton shower via the SoftDrop shared momentum fraction, the groomed jet radius, and the jet Mass in p+p collisions at 200 GeV as a function of jet transverse momenta. We also showcase the first measurement of iterative softdrop groomed observables for first, second and third splits with an initiator prong transverse momenta ranging from 20-25 GeV. In comparing the un-corrected data to our simulation, we are able to look at snapshots of the jet clustering history leading towards an understand of the time evolution of the parton shower. Having established the p+p baseline, we present the first measurement of the jet's inherent angular structure in Au+Au collisions at 200 GeV via an experimentally robust observable the opening angle between the two leading sub-jets ($θ_{SJ}$). In Au+Au collisions at STAR, we utilize a specific di-jet selection as introduced in our previous momentum imbalance ($A_{J}$) measurement and measure both the $A_{J}$ and the recoil jet spectra differentially as a function of the angular classes based on the $θ_{SJ}$ observable. With such measurements, we probe the medium response to jets at a particular resolution scale and find no significant differences in quenching for jets of different angular scales as given by $θ_{SJ}$.
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