Access to Photon Fragmentation Functions in Hadronic Jet Production

Abstract

We argue that the process $pp\to (\text{jet}\gamma )X$, for which a photon is observed inside a fully reconstructed jet and is treated as part of the jet, offers new probes of the so far little known fragmentation functions for photons. We present a next-to-leading-order QCD calculation of the cross section for this process in the limit that the jet is relatively narrow. We also investigate the background resulting from the two-photon decay of neutral pions. We present numerical results relevant for possible measurements at the LHC and at RHIC. These suggest that $pp\to (\text{jet}\gamma )X$ should provide clean access to the photon fragmentation functions, provided an efficient suppression of the background is available in experiment.

16 pages, 3 figures; Minor changes, 1 Ref. added. Version to appear in PRD