Kinematic distributions of the ηc photoproduction in ep collisions within the nonrelativistic QCD framework
Kinematic distributions of the ηc photoproduction in ep collisions within the nonrelativistic QCD framework
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DOI：
10.1103/physrevd.99.114018
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发表时间：
2019-02
影响因子：
5
通讯作者：
Hong-Fei Zhang;Yu Feng;Wen-Long Sang;Yu-peng Yan
中科院分区：
文献类型：
--
作者：
Hong-Fei Zhang;Yu Feng;Wen-Long Sang;Yu-peng Yan
本文研究了$ep$碰撞中的$\eta_c$光生。$c\bar{c}（^1S_0^{[1]}）$、$c\bar{c}（^1S_0^{[8]}）$、$c\bar{c}（^3S_1^{[8]}）$和$c\bar{c}（^1P_1^{[8]}）$的短程系数在$\alpha_s$展开中以领先顺序计算，其中首次实现了色单态贡献。我们仔细分析了截面的不同运动学分布，发现与色八重态部分相比，色单重态部分的贡献被大大抑制。这一特性使得$\eta_c$光生过程成为检验非相对论QCD中色八重态机制的理想实验室。通过采用不同的长距离矩阵元素集，我们观察到一些明显可区分的预测，这些预测可以用来仔细检查这些矩阵元素的有效性。
We study the $\eta_c$ photoproduction in $ep$ collisions in this paper. The short-distance coefficients for $c\bar{c}(^1S_0^{[1]})$, $c\bar{c}(^1S_0^{[8]})$, $c\bar{c}(^3S_1^{[8]})$, and $c\bar{c}(^1P_1^{[8]})$ photoproductions are evaluated at leading order in $\alpha_s$ expansion, where the color-singlet contribution is achieved for the first time. We have carefully analyzed different kinematic distributions of the cross sections and found that the color-singlet contribution is considerably suppressed comparing with the color-octet parts. This feature renders the $\eta_c$ photoproduction process an ideal laboratory to test the color-octet mechanism in nonrelativistic QCD. By taking different sets of long-distance matrix elements, we have observed some apparently distinguishable predictions, which can be utilized to scrutinize the validity of these matrix elements.