Systematic Improvement of Parton Showers with Effective Theory

TL;DR

This paper develops a systematic method to improve parton shower simulations by incorporating next-to-leading order power corrections through effective field theory, enhancing accuracy in modeling particle collisions.

Contribution

It introduces a novel mapping between parton shower ingredients and effective field theory operators, enabling systematic classification and computation of power corrections.

Findings

Classified branching corrections into hard-scattering and jet-structure types.

Derived a framework to include matrix elements with additional hard partons.

Maintained localization of interference structures in the shower.

Abstract

We carry out a systematic classification and computation of next-to-leading order kinematic power corrections to the fully differential cross section in the parton shower. To do this we devise a map between ingredients in a parton shower and operators in a traditional effective field theory framework using a chain of soft-collinear effective theories. Our approach overcomes several difficulties including avoiding double counting and distinguishing approximations that are coordinate choices from true power corrections. Branching corrections can be classified as hard-scattering, that occur near the top of the shower, and jet-structure, that can occur at any point inside it. Hard-scattering corrections include matrix elements with additional hard partons, as well as power suppressed contributions to the branching for the leading jet. Jet-structure corrections require simultaneous consideration of potential 1 -> 2 and 1 -> 3 branchings. The interference structure induced by collinear terms with subleading powers remains localized in the shower.