发表机构
Institute of Physics, Academia Sinica（中央研究院物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究结合\textsc{Pythia}建模的靶碎裂贡献与OPE贡献，重现HERA领头中子数据，还给出未来EIC上领头中子产生的预测，以扩展对小$x_\pi$的敏感性。
AI 中文摘要
HERA上H1和ZEUS实验的领头中子电产生测量数据已被用于在沙利文单介子交换（OPE）框架内约束小动量分数下的介子部分子分布函数（PDFs），补充了来自介子诱导的Drell-Yan测量对大$x_\pi$的约束。此前分析主要聚焦于大中子纵向动量分数$x_L$区域，该区域深度非弹性散射（DIS）靶碎裂的贡献被抑制。本研究使用\textsc{Pythia}事件发生器对靶碎裂贡献进行建模，表明其与OPE贡献的结合可在整个测量的$x_L$范围内重现HERA领头中子数据的主要特征，且无需引入额外的特设归一化因子。该结果证明了将更广泛的领头中子数据纳入未来全局分析的潜力，从而扩展对更小介子动量分数$x_\pi$的敏感性。研究还调查了与介子-核子顶点形状因子相关的模型依赖性，表明HERA数据对\textsc{Pythia}中实现的不同靶碎裂处理方式敏感。最后，本研究给出了未来美国电子离子对撞机（EIC）上领头中子产生的预测，确定了能增强对介子结构敏感性同时抑制DIS靶碎裂贡献的束流能量配置和运动学区域。
英文摘要
Leading-neutron electroproduction measurements from the H1 and ZEUS experiments at HERA have been used to constrain pion parton distribution functions (PDFs) at small momentum fractions within the Sullivan one-pion-exchange (OPE) framework, complementing large-$x_π$ constraints from pion-induced Drell--Yan measurements. Previous analyses have focused primarily on the region of large neutron longitudinal momentum fraction, $x_L$, where contributions from deep-inelastic scattering (DIS) target fragmentation are suppressed. In this work, we use the \textsc{Pythia} event generator to model the target-fragmentation contribution and show that its combination with the OPE contribution reproduces the main features of the HERA leading-neutron data over the full measured $x_L$ range without introducing additional ad hoc normalization factors. This result demonstrates the potential of incorporating a broader range of leading-neutron data into future global analyses, thereby extending sensitivity to smaller pion momentum fractions $x_π$. We investigate the model dependence associated with the pion--nucleon vertex form factor and show that the HERA data are sensitive to different target-fragmentation treatments implemented in \textsc{Pythia}. Finally, we present projections for leading-neutron production at the future U.S. Electron-Ion Collider (EIC), identifying beam-energy configurations and kinematic regions that provide enhanced sensitivity to pion structure while suppressing DIS target-fragmentation contributions.
Comments32 pages, 24 figures
