NLO QED corrections to ISR in e+ e- annihilation and the measurement of σ(e+ e- \to hadrons) using tagged photons

The leptonic tensor for the process e+e−→γ+γ∗, which describes the next-to-leading order virtual and soft QED corrections to initial state radiation in e+e− annihilation with emission of an extra virtual photon decaying into hadrons, is calculated. A Monte Carlo generator for the reaction e+e−→γ+π+π− has been set up which includes these corrections. It thus describes configurations where the invariant mass of the hadrons plus photon is very close to s√. Predictions for cms energies of 1 to 10 GeV, corresponding to the energies of DAPHNE and B-meson factories, are presented. The possibility for an accurate measurement using tagged photons of σ(e+e−→hadrons), which plays an important role in …