Fooling around with the Sudakov veto algorithm

The Sudakov veto algorithm for generating emission and no-emission probabilities in parton showers is revisited and some oversampling and reweighting techniques are suggested, mainly to improve statistics. Specifically we consider the generation of Sudakov form factors in algorithms of CKKW type for matrix element/parton shower merging, both at tree- and loop-level, and the generation of highly suppressed splittings inside standard parton showers. (orig.)