Helicity-dependent showers and matching with VINCIA

Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. We present an antenna shower formalism that includes helicity dependence for massless partons. The formalism applies to both traditional (global) showers and sector-based variants. We combine the shower with VINCIA's multiplicative approach to matrix-element matching, generalized to operate on each helicity configuration separately. The result is a substantial gain in computational speed for high parton multi-plicities. We present an implementation of both sector and global showers, with min/max variations, and helicity-dependent tree-level matching applied through n 4 for V=H ! q " q þ n partons and through n 5 for H ! n gluons.