Probing the Structure of Jets: Factorized and Resummed Angularity Distributions in SCET

TL;DR

This paper uses soft-collinear effective theory to factorize and resum angularity distributions in electron-positron collisions, incorporating nonperturbative effects with a universal soft function model.

Contribution

It provides the first calculation of angularity distributions for all a<1 at NLL accuracy, including a universal nonperturbative soft function model.

Findings

Calculated jet and soft functions for all a<1 at first order in α_s

Resummed large logarithms to NLL accuracy

Implemented a universal nonperturbative soft function model

Abstract

Using the framework of soft-collinear effective theory (SCET), we factorize and calculate $e^+e^-$ angularity distributions, including perturbative resummation and the incorporation of a universal model for the nonperturbative soft function. Angularities $\tau_a$ are a class of event shapes varying in their sensitivity to the substructure of jets in the final state, controlled by a continuous parameter $a<2$. We calculate the jet and soft functions in factorized angularity distributions for all $a<1$ to first order in the strong coupling $\alpha_s$ and resum large logarithms to next-to-leading logarithmic (NLL) accuracy. We employ a universal model for the nonperturbative soft function with a gap parameter which cancels the renormalon ambiguity in the partonic soft function.