Parton Showers beyond Leading Logarithmic Accuracy.

Mrinal Dasgupta,Keith Hamilton,Pier Francesco Monni,Gavin P Salam,Grégory Soyez,Frédéric A Dreyer

doi:10.1103/physrevlett.125.052002

Abstract

Parton showers are among the most widely used tools in collider physics. Despite their key importance, none so far have been able to demonstrate accuracy beyond a basic level known as leading logarithmic order, with ensuing limitations across a broad spectrum of physics applications. In this Letter, we propose criteria for showers to be considered next-to-leading logarithmic accurate. We then introduce new classes of shower, for final-state radiation, that satisfy the main elements of these criteria in the widely used large-N_{C} limit. As a proof of concept, we demonstrate these showers' agreement with all-order analytical next-to-leading logarithmic calculations for a range of observables, something never so far achieved for any parton shower.

Highlights

As a proof of concept, we demonstrate these showers’ agreement with all-order analytical next-to-leading logarithmic calculations for a range of observables, something never so far achieved for any parton shower
Partons refer to quarks and gluons, and a shower aims to encode the dynamics of parton production between the high-energy scattering and the low scale of hadronic quantum chromodynamics (QCD), at which experimental observations are made
We define leading logarithmic (LL) accuracy to include a condition that the shower should generate the correct effective squared tree-level matrix element in a limit where every pair of emissions has distinctly different values for Published by the American Physical Society both logarithmic variables

Summary

Introduction

We define leading logarithmic (LL) accuracy to include a condition that the shower should generate the correct effective squared tree-level matrix element in a limit where every pair of emissions has distinctly different values for Published by the American Physical Society both logarithmic variables. At next-to-leading logarithmic (NLL) accuracy, we further require that the shower generate the correct squared tree-level matrix element in a limit where every pair of emissions has distinctly different values for at least one of the logarithmic variables (or some linear combination of their logarithms).

Results

Conclusion