Event generation from effective field theory

Abstract

A procedure is developed for using soft collinear effective theory (SCET) to generate fully exclusive events, which can then be compared to data from collider experiments. We show that SCET smoothly interpolates between QCD for hard emissions, and the parton shower for soft emissions, while resumming all large logarithms. In SCET, logarithms are resummed using the renormalization group, instead of classical Sudakov factors, so subleading logarithms can be resummed as well. In addition, all loop effects of QCD can be reproduced in SCET, which allows the effective theory to incorporate next-to-leading and higher-order effects. We also show through SCET that in the soft/collinear limit, successive branchings factorize, a fact which is essential to parton showers, and that the splitting functions of QCD are reproduced. Finally, combining these results, we present an example of an algorithm that incorporates the SCET results into an event generator which is systematically improvable.