QED BREMSSTRAHLUNG IN SEMILEPTONIC-B AND LEPTONIC TAU-DECAYS

In this paper we present seminalytical and Monte Carlo calculations of radiative corrections in semileptonic decays. For two decay channels, B+/- --> D0e+/-nuBAR(gamma) and tau --> e+/-nunuBAR(gamma), we compare numerical results on the electron spectrum from the exact analytical O(alpha) formula, the leading-log formula, and the approximate formula presently used in experimental analyses and Monte Carlo simulations. We estimate the physical precision of the presented results and propose a new prescription on how to treat QED bremsstrahlung effects in the B decays.