Speaker
Dr
Bachir Moussallam
(IPN, Universite Paris-Sud)
Description
We discuss how to generalize the classic results on photon-photon
scattering which combine dispersion theoretical constraints with
chiral symmetry and soft photon theorems to the photon-photon*(q^2)
scattering amplitude into a pion pair. This generalisation requires a
specific treatment of resonance exchange diagrams. The constructed
amplitude displays explicitly the dependence on pi-pi phase-shifts,
pion electromagnetic form factors (being also sensitive to the
omega-pi form factor puzzle) and pion polarizabilities. It is
matched to the NLO ChPT amplitude near zero energies and compared to
experimental measurements of e^+ e^- -> gamma pi0 pi0 by SND and
CMD-2 below one GeV. Applications are made to the pions generalized
polarizabilities, to the sigma meson (pole) electromagnetic form
factor and to the gamma pi pi contribution to the HVP and the muon g-2.
Primary author
Dr
Bachir Moussallam
(IPN, Universite Paris-Sud)
