Mass effects in the polarized virtual photon structure

Abstract

We discuss target mass effects in the polarized virtual photon structure functions $g_1^γ(x,Q^2,P^2)$, $g_2^γ(x,Q^2,P^2)$ for the kinematic region $Λ^2\ll P^2 \ll Q^2$, where $-Q^2 (-P^2)$ is the mass squared of the probe (target) photon. We obtain the expressions for the structure functions in closed form by inverting the Nachtmann moments for the twist-2 and twist-3 operators. Numerical analysis shows that target mass effects appear at large $x$ and become sizable near the maximal value of $x$, as the ratio $P^2/Q^2$ increases. Target mass effects for the QCD sum rules of $g_1^γ$ and $g_2^γ$ are also investigated.

5 pages, LaTeX, 4 eps figures, npb.sty file included, Talk given at Loops and Legs 2004, Zinnowitz, Germany, April 25-30, 2004, to appear in the Proceedings