Generalized chiral perturbation theory and the reaction γγ → π^{0}π^{0}
Abstract
The cross section for γγ → π^{0}π^{0} and the pion polarizabilities are computed, within generalized chiral perturbation theory, in the full one loop approximation, i.e. up to and including order O( p^{5}). The result depends on the parameter α _{ππ} defining the tree level ππ scattering amplitude and on an additional low energy constant. The latter is shown to be related by an exact sumrule to the e^{+}e^{} data. The parameter α _{ππ} is related to the quark mass ratio r = m _{s}/m̂ via the expansion of pseudoscalar meson masses. The generalized one loop γγ → π^{0}π^{0} amplitude agrees with the experimental data in the threshold region provided r = m _{s}/m̂ ≲ 10. Higher order corrections are estimated comparing our calculation with the dispersive approach.
 Publication:

Nuclear Physics B
 Pub Date:
 October 1994
 DOI:
 10.1016/S05503213(94)800448
 arXiv:
 arXiv:hepph/9402318
 Bibcode:
 1994NuPhB.429..125K
 Keywords:

 High Energy Physics  Phenomenology
 EPrint:
 21 pages (plain latex)+1 fig (using feynman.tex)+ 6 figs (ps file appended), IPNO/TH 9408