Controlling inclusive cross sections in parton shower + matrix element merging

TL;DR

This paper introduces a method to improve parton shower and matrix element merging by preserving inclusive cross sections, enabling approximate NLO corrections and higher-order accuracy in particle physics simulations.

Contribution

It extends matrix element plus parton shower merging to maintain inclusive cross sections and incorporate approximate NLO corrections, enhancing simulation accuracy.

Findings

Preserves inclusive cross sections in merging algorithms.

Enables approximate NLO contributions similar to LoopSim.

Allows for NLO accuracy below the merging scale.

Abstract

We propose an extension of matrix element plus parton shower merging at tree level to preserve inclusive cross sections obtained from the merged and showered sample. Implementing this constraint generates approximate next-to-leading order (NLO) contributions similar to the LoopSim approach. We then show how full NLO, or in principle even higher order, corrections can be added consistently, including constraints on inclusive cross sections to account for yet missing parton shower accuracy at higher logarithmic order. We also show how NLO accuracy below the merging scale can be obtained.