QCD Corrections to Photon Production in Association with Hadrons in $e^{+}{e}^{-}$ Annihilation

Abstract

A detailed investigation of the theoretical ambiguities present in the QCD description of photon production in $e^{+}{e}^{-}$ annihilation is given. It is pointed out that in a well-defined perturbative analysis it is necessary to subtract the quark-photon collinear singularities. This subtraction requires the introduction of an unphysical parameter in the perturbative part of the cross section. The subtracted term is factored into non-perturbative fragmentation function. The dependence on the unphysical parameter cancels in the sum of non-perturbative and perturbative parts. It is pointed out that for $E_{\gamma }\le \sqrt{s}/(2(1+{ϵ}_c))$ the non-perturbative contributions are suppressed. Using a general purpose next-to-leading order Monte Carlo program, we calculate various physical quantities that were measured in LEP experiments recently.

Comments: 23 pages, 11 figures, 1 table (available by request), LaTeX, ETH-TH/92-26