Theoretical analysis of the γγ(*) → π0η process

Abstract

The theoretical analysis of the γγ → π0η process is presented within the energy range up to 1.4 GeV. The S -wave resonance a0(980) is described involving the coupled channel dispersive framework and the D-wave a2(1320) is approximated as a Breit-Wigner resonance. For the a0(980) the pole is found on the IV Riemann sheet resulting in a two-photon decay width of Γa0 → γγ = 0.27(4) keV. The first dispersive prediction is provided for the single-virtual γγ*(Q2) → π0η process in the spacelike region up to Q2 = 1 GeV2.