Regular Article — Theoretical Physics
Two photons into π0π0
Departamento de Física, Universidad de Murcia, E-30071, Murcia, Spain
Revised: 30 May 2008
Published online: 26 June 2008
We perform a theoretical study based on dispersion relations of the reaction γγ → π 0 π 0 emphasizing the low-energy region. We discuss how the ƒ 0(980) signal emerges in γγ → ππ within the dispersive approach and how this fixes to a large extent the phase of the isoscalar S-wave γγ → ππ amplitude above the threshold. This allows us to make sharper predictions for the cross-section at lower energies and our results could then be used to distinguish between different ππ isoscalar S-wave parameterizations with the advent of new precise data on ππ → π 0 π 0. We compare our dispersive approach with an updated calculation employing the unitary chiral perturbation theory (U gC PT). We also pay special attention to the role played by the σ-resonance in γγ → ππ and calculate its coupling and width to γγ, for which we obtain Γ(σ → γγ) = (1.68 ± 0.15) keV.
PACS: 11.55.Fv Dispersion relations – / 12.39.Fe Chiral Lagrangians – / 11.80.Et Partial-wave analysis – / 13.60.Le Meson production –
© SIF, Springer-Verlag Berlin Heidelberg, 2008