Numerical resummation at subleading color in the strongly ordered soft gluon limit

We present a Monte Carlo approach to soft-gluon resummation at subleading color which can be used to improve existing parton shower algorithms. At the single-emission level, soft-collinear enhancements of the splitting functions are explicitly linked to quadratic Casimir operators, while wide angle single-soft enhancements are connected to nontrivial color correlators. We focus on a numerically stable implementation of color matrix element corrections to all orders and approximate the virtual corrections by requiring unitarity at the single-emission level. We provide a proof-of-concept implementation to compute nonglobal event shapes at lepton colliders.
Comment: 11 pages, 3 figures, 1 table, revised claimed accuracy in response to arXiv:2003.06399, version accepted for publication in Phys. Rev. D