Recoil and power corrections inhigh−xTdirect photon production

We study a class of nonperturbative corrections to single-inclusive photon cross sections at measured transverse momentum $p_T$, in the large-$x_T$ limit. We develop an extension of the joint (threshold and transverse momentum) resummation formalism, appropriate for large $x_T$, in which there are no kinematic singularities associated with recoil, and for which matching to fixed-order and to threshold resummation at next-to-leading logarithm (NLL) is straightforward. Beyond NLL, we find contributions that can be attributed to recoil from initial-state radiation. Associated power corrections occur as inverse powers of $p_T^2$ and are identified from the infrared structure of integrals over the running coupling. They have significant energy-dependence and decrease from typical fixed-target to collider energies. Energy conservation, which is incorporated into joint resummation, moderates the effects of perturbative recoil and power corrections for large $x_T$.