Measurement of Multijet Production in ep Collisions at High Q^2 and Determination of the Strong Coupling alpha_s

TL;DR

This paper reports precise measurements of multijet production in high Q^2 ep collisions at HERA, using these data to test perturbative QCD and determine the strong coupling constant alpha_s with improved accuracy.

Contribution

It provides new, high-precision measurements of jet cross sections in deep-inelastic scattering and extracts the strong coupling constant alpha_s at the Z boson mass scale.

Findings

Measured jet cross sections as functions of Q^2, P_T^jet, and Xi.

Compared measurements with NLO QCD calculations.

Determined alpha_s(M_Z) = 0.1165 with experimental and theoretical uncertainties.

Abstract

Inclusive jet, dijet and trijet differential cross sections are measured in neutral current deep-inelastic scattering for exchanged boson virtualities 150 < Q^2 < 15000 GeV^2 using the H1 detector at HERA. The data were taken in the years 2003 to 2007 and correspond to an integrated luminosity of 351 pb^{-1}. Double differential Jet cross sections are obtained using a regularised unfolding procedure. They are presented as a function of Q^2 and the transverse momentum of the jet, P_T^jet, and as a function of Q^2 and the proton's longitudinal momentum fraction, Xi, carried by the parton participating in the hard interaction. In addition normalised double differential jet cross sections are measured as the ratio of the jet cross sections to the inclusive neutral current cross sections in the respective Q^2 bins of the jet measurements. Compared to earlier work, the measurements benefit from an improved reconstruction and calibration of the hadronic final state. The cross sections are compared to perturbative QCD calculations in next-to-leading order and are used to determine the running coupling and the value of the strong coupling constant as alpha_s(M_Z) = 0.1165 (8)_exp (38)_{pdf,theo}.