Value of alpha_s from deep-inelastic-scattering data

TL;DR

The paper addresses the precision determination of the strong coupling constant $α_s$ from deep-inelastic scattering data, focusing on reducing theoretical uncertainties from higher-order QCD corrections and high-twist contributions. It employs NNLO QCD evolution and a careful treatment of HT terms within an $x$-space DIS fit to proton and deuterium data, assessing uncertainties from HO corrections, HT effects, and heavy-quark schemes. The main result is $α_s(M_Z)=0.1143$ with quantified experimental and theoretical errors, with an indicative $N^3LO$ value around 0.113, underscoring the importance of HT modeling for robust DIS determinations. The work demonstrates that DIS can provide competitive constraints on $α_s$ when HO and HT uncertainties are rigorously managed, and it offers a framework for comparisons with world averages and other analyses.

Abstract

We report the value of $α_{\rm s}$ obtained from QCD analysis of existing data on deep-inelastic scattering of charged leptons off proton and deuterium and estimate its theoretical uncertainties with particular attention paid to impact of the high-twist contribution to the deep-inelastic-scattering structure functions. Taking into account the major uncertainties the value $α^{\rm NNLO}_{\rm s}(M_{\rm Z})=0.1143 \pm 0.0014({\rm exp.})\pm 0.0013({\rm theor.})$ is obtained. An extrapolation of the LO--NLO--NNLO results to the higher orders makes it possible to estimate $α^{\rm N^3LO}_{\rm s}(M_{\rm Z})\sim 0.113$.

Figures (4)

• Figure 1: The central values of $\alpha_{\rm s}(M_{\rm Z})$ and the experimental errors obtained in different orders of pQCD (full symbols). The open symbol shows the result of extrapolation to the N$^3$LO.
• Figure 2: Shown is the correlation coefficient for the fitted values of $\alpha_{\rm s}(M_{\rm Z})$ and $H_2^p$ at different $x$.
• Figure 3: The values of $\alpha_{\rm s}(M_{\rm Z})$ obtained from the fit with $H_{\rm 2,L}=0$ and different cuts $Q_{\rm min}$ (left panel) and the corresponding values of $\chi^2/NDP$ (right panel). The horizontal lines in the left panel correspond to the central value and the error band of $\alpha_{\rm s}(M_{\rm Z})$ in the analysis with the HT parameterized in the piece-linear form, the error bars in the right panel are $\sqrt{2/NDP}$.
• Figure 4: One-standard-deviation band for the HT term in the proton structure function $F_2$ obtained in the gradient model fit (curves) compared to the model independent determination (points).