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arXiv 1301.4502hep-ph
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SCET与微扰QCD的软重构尺度

The scale of soft resummation in SCET vs perturbative QCD

Marco Bonvini, Stefano Forte, Margherita Ghezzi, Giovanni Ridolfi

摘要:

我们总结和扩展以前的结果进行比较的阈值remmation,使用软共线有效理论(SCET),在Becher-Neubert方法,标准微扰QCD形式主义的基础上因式分解和remmation的Mellin矩的部分子截面。我们表明,这个SCET结果的对数精度可以扩展半个对数的顺序,从而使它在完全符合标准QCD结果,如果一个合适的选择是由软标度μ s的SCET结果的特点。我们提供了一个主公式有关的两种方法为其他规模的选择。然后,我们表明,与Becher-Neubert尺度的选择的朗道极点,这在微扰QCD方法通常是通过功率或指数抑制项,在SCET方法中被删除的crumically subleading项,打破因式分解。这样的条款可能成为领导的一般选择的部分子分布,并始终领先时,remation是使用足够远的强子阈值。

英文摘要:

We summarize and extend previous results on the comparison of threshold resummation, performed, using soft-collinear effective theory (SCET), in the Becher-Neubert approach, to the standard perturbative QCD formalism based on factorization and resummation of Mellin moments of partonic cross sections. We show that the logarithmic accuracy of this SCET result can be extended by half a logarithmic order, thereby bringing it in full agreement with the standard QCD result if a suitable choice is made for the soft scale mu_s which characterizes the SCET result. We provide a master formula relating the two approaches for other scale choices. We then show that with the Becher-Neubert scale choice the Landau pole, which in the perturbative QCD approach is usually removed through power- or exponentially suppressed terms, in the SCET approach is removed by logarithmically subleading terms which break factorization. Such terms may become leading for generic choices of parton distributions, and are always leading when resummation is used far enough from the hadronic threshold.

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