Timelike showers with jet recoils

TL;DR

This paper introduces a novel method for enforcing four-momentum conservation in timelike parton showers by allowing recoil to be distributed to groups of partons called jets, enhancing the accuracy of the simulation.

Contribution

It presents a new recoil scheme for dipole parton showers that maintains NLL accuracy without explicit jet clustering during evolution.

Findings

Algorithm satisfies NLL accuracy criteria

Recoil to jets is viable for dipole/antenna showers

Numerical tests confirm theoretical predictions

Abstract

We propose a new way to impose four-momentum conservation on timelike parton-shower branchings, allowing for recoil to be imparted not only to individual partons but also to groups of partons, "jets". In this work we present an explicit realisation of this idea for a dipole parton-shower, using angular ordering to decide which partons are grouped into jets in a way that does not require explicit jet clustering at each stage of the evolution. We verify that the algorithm satisfies next-to-leading logarithmic (NLL) accuracy criteria, from numerical fixed-order tests as well as resummation tests across a range of observables. Our conclusion is that jet recoils provide a viable path for adapting existing dipole/antenna-type showers to achieve NLL accuracy.