NNLO QCD analysis of the virtual photon structure functions

TL;DR

This paper performs a detailed NNLO QCD analysis of virtual photon structure functions in two-photon processes, providing theoretical predictions relevant for experimental measurements in electron-positron collisions.

Contribution

It presents the first NNLO QCD evaluation of the virtual photon structure function $F_2^rac{ ext{gamma}}{}$ and NLO for $F_L^ extrac{ ext{gamma}}{}$, including target mass effects.

Findings

NNLO corrections significantly improve theoretical accuracy.

Target mass effects are important at large x.

Phenomenological analysis of effective structure function $F_{ m eff}^ extrac{ ext{gamma}}{}$.

Abstract

The next-to-next-to-leading order (NNLO) QCD analysis is performed for the virtual photon structure functions which can be measured in the double-tag events in two-photon processes in $e^+e^-$ collisions. We investigate the perturbative QCD evaluation of $F_2^\gamma(x,Q^2,P^2)$ to NNLO and $F_L^\gamma(x,Q^2,P^2)$ to NLO with and without taking into account the target mass effects, which are relevant for the large $x$ region. We also carry out the phenomenological analysis for the experimentally accessible effective structure function $F_{\rm eff}^\gamma=F_2^\gamma+(3/2)F_L^\gamma$.