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arXiv 0909.2124hep-ph
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微扰QCD中的非单态物理演化核和大x系数函数

On non-singlet physical evolution kernels and large-x coefficient functions in perturbative QCD

S. Moch, A. Vogt

摘要:

本文研究了深度非弹性散射中味非单态观测量的物理演化核的大x行为,其中x是Bjorken变量,半包含e^+ e^-湮灭和Drell-Yan轻子对产生.与相应的MSbar方案系数函数不同,所有这些内核在1-x中的所有阶次都显示出单对数大x增强。我们推测,这种普遍的行为,建立了费曼图计算到第四阶,持有在所有的订单在强耦合常数α_s。由此产生的预测是针对高阶系数函数的最高ln^n(1-x)贡献。在Mellin-N空间中,这些预言采用了指数化的形式,然而,它似乎不如著名的软胶子指数化的前导项(1-x)^(-1)ln^n(1-x)。特别是在深度非弹性散射中,1/N修正对于所有实际相关的N都是不可忽略的。

英文摘要:

We study the large-x behaviour of the physical evolution kernels for flavour non-singlet observables in deep-inelastic scattering, where x is the Bjorken variable, semi-inclusive e^+ e^- annihilation and Drell-Yan lepton-pair production. Unlike the corresponding MSbar-scheme coefficient functions, all these kernels show a single-logarithmic large-x enhancement at all orders in 1-x. We conjecture that this universal behaviour, established by Feynman-diagram calculations up to the fourth order, holds at all orders in the strong coupling constant alpha_s. The resulting predictions are presented for the highest ln^n(1-x) contributions to the higher-order coefficient functions. In Mellin-N space these predictions take the form of an exponentiation which, however, appears to be less powerful than the well-known soft-gluon exponentiation of the leading (1-x)^(-1) ln^n(1-x) terms. In particular in deep-inelastic scattering the 1/N corrections are non-negligible for all practically relevant N.

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