Higher-Order Corrections to Timelike Jets

TL;DR

This paper introduces a new formalism for timelike jet evolution that systematically incorporates matrix element corrections, improves accuracy, and is implemented in a publicly available event generator plugin.

Contribution

It presents a simple, systematic method for including higher-order matrix element corrections in timelike jet evolution within a Markov chain framework.

Findings

Successfully incorporates corrections up to alpha_s^4

Provides a modular scheme with estimated uncertainties

Implemented in the VINCIA plugin for PYTHIA 8

Abstract

We present a simple formalism for the evolution of timelike jets in which tree-level matrix element corrections can be systematically incorporated, up to arbitrary parton multiplicities and over all of phase space, in a way that exponentiates the matching corrections. The scheme is cast as a shower Markov chain which generates one single unweighted event sample, that can be passed to standard hadronization models. Remaining perturbative uncertainties are estimated by providing several alternative weight sets for the same events, at a relatively modest additional overhead. As an explicit example, we consider Z -> q qbar evolution with unpolarized, massless quarks and include several formally subleading improvements as well as matching to tree-level matrix elements through alpha_s^4. The resulting algorithm is implemented in the publicly available VINCIA plugin to the PYTHIA 8 event generator.