Multiplicative-Accumulative matching of NLO calculations with parton showers

TL;DR

This paper introduces a novel multiplicative-accumulative matching approach to combine NLO calculations with parton showers, achieving applicability, positive weights, and clear shower attribution, enhancing accuracy and flexibility in particle physics simulations.

Contribution

It presents a new hybrid matching method that combines multiplicative and additive techniques to improve NLO and parton shower integration.

Findings

Applicable to general showers like MCatNLO and POWHEG

Produces positive-weight events similar to KrkNLO and POWHEG

Ensures all showering is attributed to the parton shower code

Abstract

We propose a new approach for combining next-to-leading order (NLO) and parton shower (PS) calculations so as to obtain three core features: (a) applicability to general showers, as with the MCatNLO and POWHEG methods; (b) positive-weight events, as with the KrkNLO and POWHEG methods; and (c) all showering attributed to the parton shower code, as with the MCatNLO and KrkNLO methods. This is achieved by using multiplicative matching in phase space regions where the shower overestimates the matrix element and accumulative (additive) matching in regions where the shower underestimates the matrix element, an approach that can be viewed as a combination of the MCatNLO and KrkNLO methods.