Measurement of $\alpha_S$ from Jet Rates in Deep Inelastic Scattering at HERA

TL;DR

This paper measures the strong coupling constant $oldsymbol{ ext{α}_s}$ at various energy scales using jet rates in deep inelastic scattering at HERA, confirming its expected running behavior with high precision.

Contribution

It provides a precise determination of $ ext{α}_s$ from jet rates in deep inelastic scattering, incorporating a new angular cut to reduce uncertainties and extrapolating to the Z boson mass.

Findings

Measured $ ext{α}_s(M_{Z^0}) = 0.117 \, ext{±} \, 0.005 (stat) \,^{+0.004}_{-0.005} (syst_{exp}) \, ext{±} \, 0.007 (syst_{theory})$

Results are consistent with the QCD prediction of running $ ext{α}_s$

Analysis covers $Q^2$ range from 120 to 3600 GeV$^2$

Abstract

Jet production in deep inelastic scattering for $120<Q^2<3600$~GeV$^2$ has been studied using data from an integrated luminosity of 3.2~pb$^{-1}$ collected with the ZEUS detector at HERA. Jets are identified with the JADE algorithm. A cut on the angular distribution of parton emission in the $\gamma^*$-parton centre-of-mass system minimises the experimental and theoretical uncertainties in the determination of the jet rates. The jet rates, when compared to ${\cal O}$($\alpha_{s}$^2$) perturbative QCD calculations, allow a precise determination of $\alpha_{s}(Q)$ in three $Q^2$-intervals. The values are consistent with a running of $\alpha_{s}(Q)$, as expected from QCD. Extrapolating to $Q=M_{Z^0}$ yields $\alpha_{s}(M_{Z^0}) = 0.117~\pm~0.005~(stat)~^{+0.004}_{-0.005}~(syst_{exp})~ ~{\pm~0.007}~(syst_{theory})$.