Efficient Matrix-Element Matching with Sector Showers

TL;DR

This paper introduces a sector antenna-based Markovian shower algorithm that seamlessly integrates tree-level matrix elements, enhancing accuracy and efficiency in particle physics simulations, with an implementation in PYTHIA 8 for Z0 decays.

Contribution

It presents a novel sector antenna shower algorithm that automatically incorporates tree-level matrix elements and achieves high efficiency and accuracy in simulations.

Findings

Efficient matching with only one matrix-element evaluation per order.

High unweighting efficiency maintained across multiple legs.

Implementation demonstrated in PYTHIA 8 for Z0 decays.

Abstract

A Markovian shower algorithm based on "sector antennae" is presented and its main properties illustrated. Tree-level full-color matrix elements can be automatically incorporated in the algorithm and are re-interpreted as process-dependent 2 -> n antenna functions. In hard parts of phase-space, these functions generate tree-level matrix-element corrections to the shower. In soft parts, they should improve the logarithmic accuracy of it. The number of matrix-element evaluations required per order of matching is 1, with an unweighting efficiency that remains very high for arbitrary numbers of legs. Total rates can be augmented to NLO precision in a straightforward way. As a proof of concept, we present an implementation in the publicly available VINCIA plug-in to the PYTHIA 8 event generator, for hadronic $Z^0$ decays including tree-level matrix elements through ${\cal O}(\alpha_s^4)$.