Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Origin of the $k_T$ smearing in direct photon production   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
($\alpha\alpha_s^2$) 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.

30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat