arXiv 2408.063402024-08hep-ph

喷注中的热力学弦碎裂与弦密度效应

Thermodynamical string fragmentation and string density effects in jets

Robert Vertesi, Antonio Ortiz

备注：: 9 pages, 4 figures
发表信息：: Phys. Rev. D 112, 036009 (2025)
DOI：: 10.1103/tysz-8rh9

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AI总结：

本文通过消除选择偏差、关闭MPI并对比PYTHIA 8的不同碎裂模型，发现热力学弦碎裂结合弦紧密堆积机制能预测喷注重子增强及类径向流效应，且色弦结可能在喷注重味重子产生中起关键作用。

摘要：

已有研究提出通过在质子-质子（pp）碰撞中观测高喷注带电组分多重数（$N_{\rm j,ch}$）来寻找部分子碎裂过程中产生的热性质和集体性质。该提议最初使用集成了多部分子相互作用（MPI）和基于MPI的色重联（CR）模型的PYTHIA 8事件生成器（Monash调谐版本）进行测试，但这些研究未发现径向流存在的确凿证据。本文通过消除与带电粒子多重数触发相关的选择偏差，扩展了上述蒙特卡洛研究；此外，我们关闭了MPI以专门聚焦于喷注碎片。我们分析了用PYTHIA 8模拟的质心系能量$\boldsymbol{\text{\textbackslash}sqrt{\text{s}}=13}$ TeV pp碰撞，探索了生成器的不同实现方案：热力学弦碎裂模型和标准Lund碎裂模型，同时还研究了色弦结的影响。令人惊讶的是，热力学弦碎裂结合弦紧密堆积机制预测了喷注中重子增强的迹象。此外，轻味重子-介子比作为$j_{\rm T}$的函数在所有PYTHIA 8实现中表现出相似性，并暗示了类径向流效应；相比之下，低$j_{\rm T}$下的重味强子比（\boldsymbol{\text{\textbackslash}LcToDz}）作为$N_{\rm j,ch}$的函数，其趋势与最小偏置数据中作为带电粒子多重数函数观测到的趋势相似，这表明色弦结可能在喷注重味重子产生中起关键作用。同一机制还预测，$j_{\rm T}$积分的\boldsymbol{\text{\textbackslash}LcToDz}比随$N_{\rm j,ch}$增加而增加。

英文摘要：

It has been proposed to search for thermal and collective properties arising from parton-fragmentation processes by examining high jet charged-constituent multiplicities ($N_{\rm j,ch}$) in proton-proton (pp) collisions. This proposal was initially tested using the PYTHIA~8 event generator with the Monash tune, which incorporates multiparton interactions (MPI) and the MPI-based colour reconnection (CR) model. These studies did not reveal any conclusive evidence for the presence of radial flow. In this paper, we expand upon the proposed Monte Carlo study by eliminating selection biases associated with triggering on charged particle multiplicities. Furthermore, MPI are disabled to focus exclusively on jet fragments. We analyse pp collisions at $\sqrt{s}$=13 TeV simulated with PYTHIA~8, exploring different implementations of the generator: thermodynamical string fragmentation and the standard Lund fragmentation model. The impact of colour-string juctions was also explored. Surprisingly, the thermodynamical string fragmentation together with the close-packing of strings mechanism predicts a hint of baryon enhancement in jets. Additionally, the light-flavor baryon-to-meson ratios as a function of $j_{\rm T}$ exhibit similarities across all PYTHIA~8 implementations, and hint at radial flow-like effects. In contrast, the ratio of heavy-flavor hadrons (\LcToDz) at low $j_{\rm T}$ as a function of $N_{\rm j,ch}$ shows a trend similar to that observed as a function of charged-particle multiplicity in minimum-bias data, suggesting that colour-string junctions may play a crucial role in heavy baryon production in jets. The same mechanism also predicts a $j_{\rm T}$-integrated \LcToDz ratio that increases with increasing $N_{\rm j,ch}$.

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