LHAPDF中的光子碎裂函数：现有集合与基于Pythia的提取
Photon Fragmentation Functions in LHAPDF: Existing Sets and a Pythia-Based Extraction
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中文总结 AI 辅助
本研究从Pythia簇射事例提取光子碎裂函数并存储于LHAPDF，对比插值方式并定义面向对撞机的包络集合，为相关唯象学研究提供便携基线。
中文摘要 AI 辅助
具有实验相关隔离判据的直接光子预测仍保留对部分子到光子碎裂函数的残余依赖，其唯象学不确定性仍仅受到较弱约束。我们开展一项实用研究，从Pythia部分子簇射事例中提取光子碎裂函数并存储于LHAP格点中。我们简要回顾光子碎裂在微扰量子色动力学中的作用，随后构造与味相关的函数$D^{\mathrm{PS}}_{\gamma/i}(z,\mu_D)$的簇射水平估计，该函数是光子动量分数$z$和碎裂标度$\mu_D$的函数。提取的分布显示出夸克与胶子道之间预期的定性层级，且碎裂贡献随标度增大而增加。同时，我们将常用的BFG、GRV和GDRG参数化转换为LHAP格点并研究其插值。我们发现LHAP中默认的对数三次插值比传统实现中常用的线性插值更忠实地再现了列表化碎裂函数的非平凡$z$和标度依赖。我们还基于BFG和GRV族定义了一个简单的面向对撞机的包络集合。这些结果为未来的唯象学研究和更系统的光子碎裂函数提取提供了便携基线。
英文摘要
Prompt-photon predictions with experimentally relevant isolation criteria retain a residual dependence on parton-to-photon fragmentation functions, whose phenomenological uncertainties remain only weakly constrained. We present a pragmatic study of photon fragmentation functions extracted from Pythia parton-shower events and stored in LHAPDF grids. We briefly review the role of photon fragmentation in perturbative QCD and then construct shower-level estimates of the flavour-dependent functions $D^{\mathrm{PS}}_{γ/i}(z,μ_D)$ as functions of the photon momentum fraction $z$ and fragmentation scale $μ_D$. The extracted distributions show the expected qualitative hierarchy between quark and gluon channels and an increasing fragmentation contribution with scale. In parallel, we convert the commonly used BFG, GRV, and GDRG parameterizations into LHAPDF grids and study their interpolation. We find that the default logcubic interpolation in LHAPDF reproduces the non-trivial $z$- and scale-dependence of the tabulated fragmentation functions more faithfully than the linear interpolation commonly used in legacy implementations. We also define a simple collider-oriented envelope set, based on the BFG and GRV families. These results provide a portable baseline for future phenomenological studies and for more systematic extractions of photon fragmentation functions.
发表机构
- INFN（意大利国家核物理研究所）
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