Recoil and Power Corrections in High-x_T Direct-Photon Production

Abstract

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.

22 pages, 4 figures as epsi, one reference added

References in corpus (5)

• Principles of general final-state resummation and automated implementation
• Parton intrinsic motion in inclusive particle production: unpolarized cross sections, single spin asymmetries and the Sivers effect
• Resummed event shapes at hadron-hadron colliders
• Scaling of Power Corrections for Angularities from Dressed Gluon Exponentiation
• Measurement of direct photon production at Tevatron fixed target energies

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• Evaluating Results from the Relativistic Heavy Ion Collider with Perturbative QCD and Hydrodynamics
• Power Corrections to Electroweak Boson Production from Threshold Resummation
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