近日，西南大学的桑文龙及其研究小组与美国阿贡国家实验室的Yingsheng Huang等人合作并取得一项新进展。经过不懈努力，他们成功在对撞机中通过粲夸克碎片产生完全粲四夸克。相关研究成果已于2024年9月2日在国际知名学术期刊《高能物理杂志》上发表。

在非相对论量子色动力学（NRQCD）框架下，该研究团队计算了粲夸克碎裂为S波全粲四夸克态（记作T_4c）的碎裂函数。粲夸克到T_4c的碎裂函数表示为可微扰计算的短程系数和非微扰的长程矩阵元（LDMEs）的乘积之和。短程系数通过α_s展开最低阶的微扰匹配程序确定。

长程矩阵元使用T_4c在原点处的四体波函数进行近似，这些波函数已通过文献中的各种现象学势模型进行评估。结合著名的QCD因子化和粲夸克到T_4c的碎裂函数，研究人员预测了在高横动量p_T区域对撞机中T_4c的产生率。研究人员在大型强子对撞机（LHC）上预测了p_T的微分分布和总截面。T_4c态产生的截面可以达到几fb到几百fb，表明LHC上T_4c事件产生具有很大潜力。

此外，研究人员还估算了电子-质子（ep）碰撞中T_4c的光产生。观察到，这些过程的截面在HERA和EIC上适中，在EicC上相对较小。考虑到这些对撞机的亮度，在ep对撞机上探测这些全粲四夸克态的前景具有一定挑战性。

附：英文原文

Title: Producing fully-charmed tetraquarks via charm quark fragmentation in colliders

Author: Bai, Xiao-Wei, Feng, Feng, Gan, Chang-Man, Huang, Yingsheng, Sang, Wen-Long, Zhang, Hong-Fei

Issue&Volume: 2024-09-02

Abstract: Within the framework of nonrelativistic QCD (NRQCD), we calculate the fragmentation function for a charm quark into an S-wave fully-charmed tetraquark, denoted as T_4c. The charm-to-T_4c fragmentation function is expressed as a sum of products of the perturbatively calculable short-distance coefficients and the nonperturbative long-distance matrix elements (LDMEs). The short-distance coefficients are ascertained through the perturbative matching procedure at lowest order in α_s expansion. The LDMEs are approximated using the T_4c four-body wave functions at the origin, which have been evaluated by various phenomenological potential models in literature. Incorporating the celebrated QCD factorization and the charm-to-T_4c fragmentation function, we predict the T_4c production rate at high transverse momentum pT regime in colliders. Both the differential distribution over pT and the integrated cross sections are predicted at the LHC. The cross sections for T_4c states production can reach several femtobarns to several hundreds femtobarns, suggesting a substantial potential for T_4c event production at the LHC. Additionally, we estimate for the photoproduction of T_4c in electron-proton (ep) collisions. It is observed that the cross sections for these processes are moderate at the HERA and EIC, and relatively small at the EicC. Given the luminosities of these colliders, the prospect of detecting these fully-charmed tetraquarks at ep colliders is somewhat challenging.

DOI: 10.1007/JHEP09(2024)002

Source: https://link.springer.com/article/10.1007/JHEP09(2024)002