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arXiv 0712.3732hep-ph
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CGC中胶子产生的共线奇点和运行耦合修正

Collinear Singularities and Running Coupling Corrections to Gluon Production in CGC

Yuri V. Kovchegov, Heribert Weigert

摘要:

分析了在CGC框架下计算的弹核碰撞胶子产生截面的运行耦合修正的结构。我们认为,胶子生产截面(和胶子横动量谱和多重性)的运行耦合修正的列入带来了共线奇异性,由于最终状态分裂完全不受CGC的修正。因此,尽管存在饱和/CGC动力学,胶子产生截面并不是红外安全的。像往常一样,正则化奇点需要一个红外截止Lambda_coll来定义胶子的分辨率尺度。我们特别指出,在强耦合常数alpha_s(Lambda_coll^2)的自变量中,截断进入胶子产生截面。我们认为,强子生产的计算应该能够吸收共线的分歧到一个碎裂功能。胶子产生截面中的奇异共线项对所产生物质的能量密度没有贡献,而所产生的物质实际上是一个红外有限量。

英文摘要:

We analyze the structure of running coupling corrections to the gluon production cross section in the projectile-nucleus collisions calculated in the Color Glass Condensate (CGC) framework. We argue that for the gluon production cross section (and for gluon transverse momentum spectra and multiplicity) the inclusion of running coupling corrections brings in collinear singularities due to final state splittings completely unaffected by CGC resummations. Hence, despite the saturation/CGC dynamics, the gluon production cross section is not infrared-safe. As usual, regularizing the singularities requires an infrared cutoff Lambda_coll that defines a resolution scale for gluons. We specifically show that the cutoff enters the gluon production cross section in the argument of the strong coupling constant alpha_s(Lambda_coll^2). We argue that for hadron production calculations one should be able to absorb the collinear divergence into a fragmentation function. The singular collinear terms in the gluon production cross section are shown not to contribute to the energy density of the produced matter, which is indeed an infrared-finite quantity.

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