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

The leptonic tensor for the process e(+)c(-) --> gamma + gamma*, 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(+)c(-) --> gamma + pi (+)pi (-) 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(1/2). 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 sigma (e(+)e(-) --> hadrons), which plays an important role in the theoretical description of the muon anomalous magnetic moment and the running of the electromagnetic coupling, is discussed.