Origin of the $k_T$ smearing in direct photon production

Paper

Abstract

We show that the Sudakov factor from the resummation of double logarithms

contained in the distribution functions is responsible for the

smearing mechanism employed in the next-to-leading-order QCD (

) calculations of direct photon production.

is the center-of-mass energy, and

the transverse momentum carried by a parton in a colliding hadron. This factor exhibits the appropriate

-dependent Gaussian width in

, such that our predictions are in good agreement with experimental data.