The Angantyr model for heavy-ion collisions in Pythia8
The Angantyr model for heavy-ion collisions in Pythia8
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DOI：
10.1007/jhep10(2018)134
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发表时间：
2018-10
影响因子：
5.4
通讯作者：
C. Bierlich;G. Gustafson;L. Lönnblad;H. Shah
中科院分区：
文献类型：
--
作者：
C. Bierlich;G. Gustafson;L. Lönnblad;H. Shah
提出了一个在高能核碰撞中建立完全排斥强子末态的新模型。它是高能pp碰撞的直接外推（如Pythia所描述的），因此弥合了重离子和高能物理现象学之间的大部分现有差距。该模型的灵感来自旧的Fritiof模型和受伤的核子的概念。两个基本特征是在每个NN子碰撞的多部分子相互作用和衍射激发的治疗。衍射激发与核子部分子结构中的波动有关，并且在这里首次包括了射弹和靶中的波动。该模型能够很好地描述一般的末态性质，如多重数和横向动量分布，无论是在PA和AA碰撞。因此，该模型可以作为一个基线，了解非集体的背景下，对集体行为敏感的可观测。由于Pythia不包括再现pp碰撞中所见的集体效应的机制，因此这些效应也不能由Angantyr的当前版本再现。在未来的研究中，将增加高弦密度的影响，如更高的奇异值比和pp中的脊。
We present a new model for building up complete exclusive hadronic final states in high energy nucleus collisions. It is a direct extrapolation of high energy pp collisions (as described by P ythia), and thus bridges a large part of the existing gap between heavy ion and high energy physics phenomenology. The model is inspired by the old Fritiof model and the notion of wounded nucleons. Two essential features are the treatment of multi-parton interactions and diffractive excitation in each NN sub-collision. Diffractive excitation is related to fluctuations in the nucleon partonic sub-structure, and fluctuations in both projectile and target are here included for the first time. The model is able to give a good description of general final-state properties such as multiplicity and transverse momentum distributions, both in pA and AA collisions. The model can therefore serve as a baseline for understanding the non-collective background to observables sensitive to collective behaviour. As P ythia does not include a mechanism to reproduce the collective effects seen in pp collisions, such effects are also not reproduced by the present version of Angantyr. Effects of high string density, shown to be able to reproduce eg higher strangeness ratios and the ridge in pp, will be added in future studies.