A framework for second-order parton showers

A framework is presented for including second-order perturbative corrections to the radiation patterns of parton showers. The formalism allows to combine O(alpha(2)(s))-corrected iterated 2 -> 3 kernels for ordered gluon emissions with tree-level 2 -> 4 kernels for unordered ones. The combined Sudakov evolution kernel is thus accurate to O(alpha(2)(s)). As a first step towards a full-fledged implementation of these ideas, we develop an explicit implementation of 2 -> 4shower branchings in this letter. (C) 2017 The Author(s). Published by Elsevier B.V.