Global fit to the charged leptons DIS data: \boldmath{$α_{\rm s}$,} parton distributions, and high twists

TL;DR

This work delivers a comprehensive global NLO QCD analysis of world charged-lepton DIS data to extract parton distribution functions, the strong coupling constant $α_s$, and twist-4 (HT) contributions, with full propagation of systematic-error correlations. It employs a direct numerical solution of DGLAP, includes target-mass corrections and HT terms, and models heavy-quark contributions via photon-gluon fusion, while assessing theoretical uncertainties through scale and threshold variations. The study finds $α_s(M_Z)=0.1165 ext{(stat+syst)}^{+0.0026}_{-0.0034}( ext{theor})$ and provides PDFs with experimental uncertainties, highlighting correlations and model dependence. It also quantifies parton-luminosity uncertainties for FNAL and LHC, informing collider phenomenology and offering a Monte Carlo-ready tool for uncertainty propagation.

Abstract

We perform the NLO QCD analysis of the world data on inclusive deep inelastic scattering cross sections of charged leptons off the proton and the deuterium targets. The parton distributions, the value of strong coupling constant $α_{\rm s}$, and the twist 4 contributions to the structure functions $F_2$ and $F_{\rm L}$ are extracted with the complete account for the correlations of data points due to the systematic errors. Sensitivity of the $α_{\rm s}$ value and the high twist contribution to the procedures of accounting for the systematic errors is studied. The impact of theoretical uncertainties on the value of $α_{\rm s}$ and on the parton distributions is analysed. The obtained value of strong coupling constant with the account of these uncertainties is $α_{\rm s}(M_{\rm Z})=0.1165\pm0.0017({\rm stat+syst}) \pm^{0.0026}_{0.0034}({\rm theor})$. The uncertainties of parton-parton luminosities for the FNAL and LHC colliders are estimated.

Figures (14)

• Figure 1: $\Delta$ is relative precision of our code used for the evolution equations integration. Indices $u$ and $d$ correspond to the valence quarks; $S$, to the sea quarks; $G$, to gluon.
• Figure 2: The distribution of diagonalized residuals for the ZEUS and H1 data (full curves: normal distribution, dashes: the Gauss distribution with the dispersion and the mean equal to the dispersion and the mean of the residuals distribution). All curves are normalized to the number of points in each experiment.
• Figure 3: The 1$\sigma$ experimental error bands for our PDFs at $Q^2=9~{\rm GeV}^2$ (full lines). For comparison the nominal MRST99 (dots) and CTEQ5 (dashes) PDFs are also given.
• Figure 4: The relative experimental PDFs errors [%] (full lines: the total errors, dashes: the experimental ones). For comparison the relative experimental errors on the PDFs of Ref.Alekhin:1999za are also given (dots).
• Figure 5: The ratio of the systematic errors on the fitted PDFs to the statistical ones (full lines: the gluon distribution; dashes: the total sea one; dots: the $d$-quark one; dotted-dashes: the $u$-quark one).