Determination of the strong coupling from high-energy data

TL;DR

This paper extracts the strong coupling constant _s(m_Z) from high-energy collider data, demonstrating that appropriate kinematic cuts and neglecting higher-twist effects lead to a stable and precise determination.

Contribution

It provides a new determination of _s(m_Z) using combined collider and DIS data with specific kinematic cuts, emphasizing the importance of removing power corrections for accuracy.

Findings

_s(m_Z,N_f=5)=0.1152  0.008 with Q^2>10 GeV^2

Stability of _s at high Q^2 cuts when higher-twist effects are suppressed

Lower Q^2 cuts lead to higher _s values and poorer fits.

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 $\alpha_s(m_Z)$ 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 $\alpha_s(m_Z,N_f=5)=0.1152 \pm 0.008$ 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.