Multipion production in photon-photon collisions

Abstract

The magnitudes of the matrix elements for γγ→2π⁺2π⁻, γγ→π⁺π⁻2π⁰, γγ→2π⁺2π⁻π⁰, γγ→2π⁺2π⁻2π⁰, γγ→3π⁺3π⁻3π⁺ and γγ→3π⁺3π⁻π⁰are deduced from experimental data as a function of the invariant massW of the system (from 1.0 to 3.0 GeV). It is shown that the data are consistent with a universal energy dependence of the reduced channel amplitudes. A statistical model is shown to describe the peaks in the energy dependence of multipion production in γγ collisions quite well without introducing explicit intermediate resonances.