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arXiv 1012.4098hep-phhep-ex
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$k_T$分解中π介子形状因子的次引导阶修正

Next-to-leading-order correction to pion form factor in $k_T$ factorization

Hsiang-nan Li, Yue-Long Shen, Yu-Ming Wang, Hao Zou

摘要:

在$k_T$分解定理中,我们计算了π介子电磁形状因子在超前扭曲处的次超前阶(NLO)修正。用$k_T^2$在夸克图和有效夸克图中考虑了离壳的部分子,得到了与横动量相关的π波函数.通过旋转Wilson线使其远离光锥,从而使TMD π波函数中的光锥奇点正则化。初态和终态部分子之间胶子交换的软发散正好抵消。通过取上述两组图的差,我们导出了π电磁形状因子的红外有限$k_T$依赖的非线性光学硬核。改变重整化和因式分解尺度,我们发现,非线性光学校正是较小的,当这两个尺度设置为不变质量的内部粒子:它变得低于40%的领先阶(LO)的贡献的动量转移平方$Q^2>7$ GeV $^2$。结果表明,非线性光学超前扭转修正在解释实验数据中并不起重要作用,但本振高扭转贡献起重要作用。

英文摘要:

We calculate next-to-leading-order (NLO) correction to the pion electromagnetic form factor at leading twist in the $k_T$ factorization theorem. Partons off-shell by $k_T^2$ are considered in both quark diagrams and effective diagrams for the transverse-momentum-dependent (TMD) pion wave function. The light-cone singularities in the TMD pion wave function are regularized by rotating the Wilson lines away from the light cone. The soft divergences from gluon exchanges among initial- and final-state partons cancel exactly. We derive the infrared-finite $k_T$-dependent NLO hard kernel for the pion electromagnetic form factor by taking the difference of the above two sets of diagrams. Varying the renormalization and factorization scales, we find that the NLO correction is smaller, when both the scales are set to the invariant masses of internal particles: it becomes lower than 40% of the leading-order (LO) contribution for momentum transfer squared $Q^2>7$ GeV$^2$. It is observed that the NLO leading-twist correction does not play an essential role in explaining the experimental data, but the LO higher-twist contribution does.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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