Scale Optimisation and Event Shapes in Deep-Inelastic Scattering

TL;DR

This paper investigates how optimizing renormalisation and factorisation scales affects perturbative calculations of event shape means in deep-inelastic scattering, revealing that separate scale choices can significantly reduce power corrections but introduce new fitting challenges.

Contribution

It introduces the concept of separate renormalization scales for quark- and gluon-initiated subprocesses in DIS, improving the accuracy of perturbative predictions.

Findings

Separate scales greatly reduce power corrections.

Optimization effects are small for standard scale choices.

Fitting low energy data remains challenging with new scale schemes.

Abstract

We study the effect of optimising the renormalisation and factorisation scales on perturbative calculations of event shape means defined in the Breit frame of ep DIS. Unlike in the case of e^+e^- event shape means, this has only a small effect on the NLO QCD predictions and a large power correction is still required to fit the data. However, if separate renormalization scales are introduced for the quark- and gluon-initiated sub-processes the optimisation has a much larger effect and greatly reduces the size of the required power corrections. Unfortunately, there are then problems fitting the low energy data for some observables.