Precision determination of alpha_s using an unbiased global NLO parton set

TL;DR

This paper accurately determines the strong coupling constant alpha_s at the Z boson mass scale using a comprehensive NLO analysis of diverse experimental data, emphasizing the importance of a global dataset for reliable results.

Contribution

It provides a precise NLO determination of alpha_s from a global dataset, highlighting the necessity of combined data for stable PDF fits and consistent alpha_s extraction.

Findings

Alpha_s(M_Z)=0.1191±0.0006 (experimental)

Deep-inelastic data alone yields alpha_s(M_Z)=0.1177±0.0009

HERA-only data results are marginally consistent with the global fit

Abstract

We determine the strong coupling alpha_s from a next-to-leading order analysis of processes used for the NNPDF2.1 parton determination, which includes data from neutral and charged current deep-inelastic scattering, Drell-Yan and inclusive jet production. We find alpha_s(M_Z)=0.1191+-0.0006 (exp), where the uncertainty includes all statistical and systematic experimental uncertainties, but not purely theoretical uncertainties. We study the dependence of the results on the dataset, by providing further determinations based respectively on deep-inelastic data only, and on HERA data only. The deep-inelastic fit gives the consistent result alpha_s(M_Z)=0.1177+-0.0009(exp), but the result of the HERA-only fit is only marginally consistent. We provide evidence that individual data subsets can have runaway directions due to poorly determined PDFs, thus suggesting that a global dataset is necessary for a reliable determination.