大型强子对撞机（LHC）喷注内的$Υ(nS)$产生
$Υ(nS)$ Production within Jets at the LHC
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中文总结 AI 辅助
本文通过次领头阶碎裂喷注函数框架研究LHC喷注内$Υ(nS)$产生，发现底夸克偶素的动量分数分布对长距离矩阵元选择不敏感，为LHC高精度测量提供理论基准。
中文摘要 AI 辅助
重夸克偶素在喷注内部的产生为量子色动力学（QCD）动力学及束缚态形成机制提供了灵敏探针。尽管近期研究表明，喷注内粲夸克偶素的可观测量能有效区分相互竞争的非相对论量子色动力学（NRQCD）长距离矩阵元（LDME）组，但该区分能力是否在底夸克偶素领域依然存在仍是待解决的问题。本文首次开展喷注内$Υ(1S)$、$Υ(2S)$和$Υ(3S)$产生的唯象研究，采用碎裂喷注函数（FJF）框架，在次领头阶（NLO）下结合DGLAP演化、阈值重求和及更高底夸克偶素态的级联衰变贡献。与粲夸克偶素形成鲜明对比，研究发现喷注内底夸克偶素的动量分数（$z_H$）分布呈现出对LDME组选择显著不敏感的普适形状，该普适性源于S波自旋三重态色八重态（$^3S_1^{[8]}$）产生机制的强主导地位，且得到$χ_b$级联衰变跃迁的强化。本文的预测既符合近期CMS实验观测到的特征性大$z_H$峰，也符合随喷注横动量增大而出现的谱展宽现象。这些结果确立了喷注内粲夸克偶素与底夸克偶素碎裂的明确物理差异，为大型强子对撞机（LHC）未来的高精度测量提供了理论基准。
英文摘要
Heavy quarkonium production inside jets offers a sensitive probe of QCD dynamics and bound-state formation mechanisms. While recent studies demonstrate that charmonium-in-jet observables effectively discriminate among competing nonrelativistic QCD (NRQCD) long-distance matrix element (LDME) sets, whether this discriminating power persists in the bottomonium sector remains an open question. Here, we present the first phenomenological study of $Υ(1S)$, $Υ(2S)$, and $Υ(3S)$ production inside jets using the fragmenting jet function (FJF) framework at next-to-leading order (NLO), incorporating DGLAP evolution, threshold resummation, and feeddown contributions from higher bottomonium states. In sharp contrast to charmonium, we find that bottomonium-in-jet momentum-fraction ($z_H$) distributions exhibit a universal shape that is remarkably insensitive to the choice of LDME sets. We show that this universality stems from the strong dominance of the S-wave spin-triplet color-octet ($^3S_1^{[8]}$) production mechanism reinforced by $χ_b$ feeddown transitions. Our predictions capture both the characteristic large-$z_H$ peak and the spectral broadening with increasing jet transverse momentum observed in recent CMS measurements. These results establish a clear physical distinction between charmonium and bottomonium fragmentation inside jets, providing a theoretical benchmark for future high-precision measurements at the LHC.
