The Alaric parton shower for hadron colliders

TL;DR

The paper introduces Alaric, a new parton shower algorithm for hadron collider simulations, enabling systematic uncertainty quantification and recoil effect studies without altering evolution variables or splitting functions.

Contribution

It presents the Alaric parton shower framework, its implementation in Sherpa, and the first multi-jet merging for this new algorithm, enhancing QCD radiation modeling.

Findings

Alaric allows studying recoil effects away from soft and collinear limits.

It provides a systematic way to quantify uncertainties in parton shower simulations.

First multi-jet merging demonstrated with the Alaric algorithm.

Abstract

We introduce the Alaric parton shower for simulating QCD radiation at hadron colliders and present numerical results from an implementation in the event generator Sherpa. Alaric provides a consistent framework to quantify certain systematic uncertainties which cannot be eliminated by comparing the parton shower with analytic resummation. In particular, it allows to study recoil effects away from the soft and collinear limits without the need to change the evolution variable or the splitting functions. We assess the performance of Alaric in Drell-Yan lepton pair and QCD jet production, and present the first multi-jet merging for the new algorithm.