Determination of the strong coupling from high-energy data

Abstract

We determine the strong coupling from high-energy data for the Drell-Yan (DY) process and top-quark hadro-production collected at the Large Hadron Collider and the Tevatron combined with the world data on deep-inelastic scattering (DIS) and fixed-target DY data. The theory description uses results at next-to-next-to-leading order in perturbative QCD in the $\overline{\mathrm{MS}}$-scheme together with leading order QED evolution. The DIS data are subject to stringent kinematic cuts to suppress the contribution of power corrections. We apply a cut on the hadronic invariant mass squared $W^2 \geq 12.5~$GeV$^2$ together with a series of cuts on momentum transfer squared $Q^2$. Discarding higher-twist terms we find that the value of strong coupling $α_s(m_Z)$ preferred by the data stabilizes at large enough cuts on $Q^2$, when low-$Q^2$ DIS data sensitive to power corrections are effectively removed. In particular, we extract the value of $α_s(m_Z,N_f=5)=0.1152 \pm 0.008$ for $N_f=5$ light flavors with the cut $Q^2>10~$GeV$^2$. In the absence of higher-twist terms less tight cuts on $Q^2$ show a clear deterioration of the fit and lead to rising values of the strong coupling, shifted upwards by about two standard deviations.

Figures (2)

• Figure 1: Kinematics of the inclusive DIS data used in the present analysis in terms of $Q^2$ and Bjorken $x$ (circles: SLAC Whitlow:1990gk, squares: BCDMS BCDMS:1989eab, triangles: NMC NewMuon:1996fwh, diamonds: HERA H1:2015ubc). The turquoise horizontal solid lines display the $Q^2$ cuts considered in the present analysis. The data points plotted at large-$x$ and low $Q^2$ all fulfill the constraint $W^2 \geq 12.5 \,\mathrm{GeV}^2$ indicated by the purple dashed line.
• Figure 2: The value of $\alpha_s(m_Z,N_f=5)$ obtained in variants of present analysis based on different combinations of data (solid squares: DIS+DY+$t$-quark data; hollow squares: the same with the high-energy data from the LHC and Tevatron dropped; hollow circles: DIS, DY fixed-target and $t$-quark data), with the cuts of $W^2>12.5~\,\mathrm{GeV}^2$ and $Q^2>Q_{\rm min}^2$ imposed on the DIS data and the HT set to zero. For comparison the values of $\alpha_s(m_Z,N_f=5)$ obtained in the ABMP16 fit Alekhin:2017kpj (upward triangle) and in the present analysis with the cuts $W>1.8~\,\mathrm{GeV}$, $Q^2>2.5~\,\mathrm{GeV}^2$ and the HT terms modeled as in Ref. Alekhin:2017kpj are given (downward triangle).