The role of the input scale in parton distribution analyses

TL;DR

This paper systematically investigates how the choice of input scale affects parton distribution analyses, revealing procedural bias impacts and proposing methods to estimate this uncertainty in QCD parameter determinations.

Contribution

It introduces a comprehensive study of input scale effects in parton distribution fits and proposes a practical procedure to estimate procedural bias.

Findings

Procedural bias significantly influences distribution results.

The input scale choice affects QCD parameter extraction.

A method to quantify this bias is proposed.

Abstract

A first systematic study of the effects of the choice of the input scale in global determinations of parton distributions and QCD parameters is presented. It is shown that, although in principle the results should not depend on these choices, in practice a relevant dependence develops as a consequence of what is called procedural bias. This uncertainty should be considered in addition to other theoretical and experimental errors, and a practical procedure for its estimation is proposed. Possible sources of mistakes in the determination of QCD parameter from parton distribution analysis are pointed out.