Single spin asymmetries in ${\gamma }^{\ast }\gamma \to \pi \pi \pi$ at large Q^2

Abstract

The ${\gamma }^{\ast }\gamma \to \pi \pi \pi$ reaction is analysed in QCD at large photon virtuality Q and small hadronic mass W. Its amplitude factorizes in a $3\pi$ generalized distribution amplitude and a hard subprocess ${\gamma }^{\ast }\gamma \to q\bar{q}$ or ${\gamma }^{\ast }\gamma \to gg$. The interference of this process with a Brehmsstrahlung process in e e or $e\gamma$ collisions gives rise to interesting single spin asymmetries, particularly when W is near the $\omega$ mass.

Comments: LaTeX, 12 pages