标题： 光子产生B_c介子的P波态 显示英文标题

标题： Photonic production of P-wave states of B_c mesons

摘要： Numerical calculations for the production of $P$-wave levels of $B_c$ quarkonium in $\gamma\gamma$ collisions are performed in the leading $O(\alpha_s^2\alpha_{em}^2)$ order of perturbation theory. The total cross-section of $P$-wave state production is about 10 % of that for the $S$-wave levels. 碎片化成分（$6+6$图）的贡献较低，基本贡献由重组机制（$8$费曼图）决定。 $\bar b\to B_c$碎片化（$6$图）的规范不变项非常准确地再现了碎片化模型的结果，而$c\to B_c$碎片化项与碎片化模型的预测存在显著偏差。 显示英文摘要

摘要： Numerical calculations for the production of $P$-wave levels of $B_c$ quarkonium in $\gamma\gamma$ collisions are performed in the leading $O(\alpha_s^2\alpha_{em}^2)$ order of perturbation theory. The total cross-section of $P$-wave state production is about 10 \% of that for the $S$-wave levels. The contribution of fragmentation component ($6+6$ diagrams) is low, and the basic contribution is determined by the recombination mechanism ($8$ Feynman diagrams). The gauge invariant term of the $\bar b\to B_c$ fragmentation ($6$ diagrams) quite accurately reproduces the result of the fragmentation model, whereas there is a strong deviation of the $c\to B_c$ fragmentation term from the predictions of the fragmentation model.