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Origin of the $k_T$ smearing in direct photon production

Hung-Liang Lai·Hsiang-nan Li
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Abstract

We show that the Sudakov factor from the resummation of double logarithms $\ln(s/k_T^2)$ contained in the distribution functions is responsible for the $k_T$ smearing mechanism employed in the next-to-leading-order QCD ($αα_s^2$) calculations of direct photon production. $s$ is the center-of-mass energy, and $k_T$ the transverse momentum carried by a parton in a colliding hadron. This factor exhibits the appropriate $s$-dependent Gaussian width in $k_T$, such that our predictions are in good agreement with experimental data.

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Hung-Liang Lai, Hsiang-nan Li. 1998-02-25. Origin of the $k_T$ smearing in direct photon production. https://doi.org/10.1103/physrevd.58.114020

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