Measurement and QCD Analysis of Jet Cross Sections in Deep-Inelastic Positron-Proton Collisions at sqrt(s) of 300 GeV

TL;DR

This study measures multi-differential jet cross sections in deep-inelastic $e^+p$ scattering at $\,\sqrt{s}=300$ GeV using the H1 detector, across a wide range of $Q^2$ and jet transverse energies in the Breit frame. By comparing to next-to-leading order QCD predictions and applying hadronization corrections, the authors extract the strong coupling constant and the proton gluon density, and perform a simultaneous determination of both alongside the quark densities. The analysis demonstrates good agreement with NLO QCD for observables with modest higher-order and non-perturbative effects, and shows that jet data provide direct sensitivity to gluons in the proton, consistent with global PDF fits. A simultaneous fit confirms the viability of constraining $\,\\alpha_s$ and PDFs with DIS jet data, highlighting the complementary role of jet cross sections to inclusive DIS in shaping our understanding of proton structure and strong coupling at high energy.

Abstract

Jet production is studied in the Breit frame in deep-inelastic positron-proton scattering over a large range of four-momentum transfers 5 < Q^2 < 15000 GeV^2 and transverse jet energies 7 < E_T < 60 GeV. The analysis is based on data corresponding to an integrated luminosity of L_int \simeq 33 pb^(-1) taken in the years 1995-1997 with the H1 detector at HERA at a center-of-mass energy sqrt(s)=300 GeV. Dijet and inclusive jet cross sections are measured multi-differentially using k_perp and angular ordered jet algorithms. The results are compared to the predictions of perturbative QCD calculations in next-to-leading order in the strong coupling constant alphas.QCD fits are performed in which alphas and the gluon density in the proton are determined separately. The gluon density is found to be in good agreement with results obtained in other analyses using data from different processes. The strong coupling constant is determined to be alphas(MZ)=0.1186+-0.0059. In addition an analysis of the data in which both alphas and the gluon density are determined simultaneously is presented.

Figures (19)

• Figure 1: Diagrams of different processes in deep-inelastic lepton-proton scattering: (a) Born process , (b) QCD-Compton process and (c) the boson-gluon fusion.
• Figure 2: A boson-gluon fusion event in deep-inelastic scattering in the boson-gluon center-of-mass frame (left) and in the Breit frame (right). The frames are related to each other by a longitudinal boost along the $z$-direction.
• Figure 3: The predictions of (a) the hadronization corrections to the dijet cross section for different jet definitions as a function of $Q^2$ as obtained by HERWIG and (b) the next-to-leading order corrections to the dijet cross section as a function of $Q^2$ for the inclusive $k_\perp$ algorithm using two different renormalization scales $\mu_r$.
• Figure 4: The inclusive jet cross section as a function of the transverse jet energy in different regions of $Q^2$ for the inclusive $k_\perp$ algorithm (left) and for the Aachen algorithm (right). The data are compared to the perturbative QCD prediction in NLO with (dashed line) and without (solid line) hadronization corrections included.
• Figure 5: The ratio of the measured inclusive jet cross section and the theoretical prediction for the inclusive $k_\perp$ algorithm (top) and the Aachen algorithm (bottom). The uncertainty of the theoretical prediction is indicated by the band (the contributions from the renormalization and factorization scale dependence and the hadronization corrections are added in quadrature).