Jet Production at Low and High $Q^2$ and Determination of the Strong Coupling $\alpha_s$ at H1

TL;DR

This paper reports measurements of jet cross sections in deep-inelastic scattering at low and high Q^2, using these data to precisely determine the strong coupling constant and observe its running over a broad energy range.

Contribution

It provides new measurements of jet cross sections at different Q^2 regimes and extracts the strong coupling constant with high precision, demonstrating its running behavior.

Findings

Jet cross sections agree with NLO perturbative QCD calculations.

Precise determination of α_s(M_Z) with experimental uncertainties of 0.6% and 1.2%.

Observation of the running of the strong coupling over a large energy range.

Abstract

Two recent measurements of inclusive jet, 2-jet and 3-jet cross sections in deep-inelastic $ep$ scattering from the H1 collaboration are presented. The measurements are performed at low $5<Q^2<100$ GeV$^2$ and high $150<Q^2<15000$ GeV$^2$ virtualities of the exchanged boson. The obtained cross sections are in good agreement with perturbative QCD calculations at NLO and are used to extract the strong coupling $\alpha_s(M_Z)$. The experimental precision is 0.6\% and 1.2\% for the high and low $Q^2$ regimes, respectively. The error on the obtained value of $\alpha_s(M_Z)$ is dominated by the theoretical uncertainties which are mostly due to missing higher orders. At low $Q^2$ the uncertainty due to terms beyond NLO amounts to 7.5\%. The determination of $\alpha_s$ at various scales shows the running of the strong coupling over a large range.