Azimuthal correlations and partial-wave analysis in photon-photon collisions.

Abstract

We are showing that, for the partial-wave analysis of exclusive $\ensuremath{\gamma}\ensuremath{\gamma}$ reactions, some useful information may be provided by the study of azimuthal correlations (involving the tagging of at least one of the photons). As an example, we consider the reaction $e\overline{e}\ensuremath{\rightarrow}e\overline{e}\ensuremath{\pi}\ensuremath{\pi}$ with $\overline{e}$ scattered at finite angle, i.e., $\ensuremath{\gamma}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$ at the resonance ${f}_{2}(1270)$, using two different $q\overline{q}$ bound-state models (nonrelativistic and relativistic) for that resonance, plus an $S$-wave contribution.