Low Q^2 Jet Production at HERA in Next-to-Leading Order QCD
G. Kramer, B. Potter
TL;DR
The paper develops a comprehensive next-to-leading order QCD calculation for jet production in electron-proton collisions at HERA across the transition from photoproduction to DIS, focusing on photon virtualities $Q^2$ in the range $Q^2$ from 1 to 100 GeV^2. It systematically combines direct and resolved virtual-photon contributions, employing phase-space slicing to handle infrared and collinear singularities and a Snowmass jet definition to align with experiments. The study finds that including the NLO corrections to the resolved component increases one- and two-jet cross sections by about 30% relative to direct-photon predictions alone, with the longitudinal photon contribution becoming non-negligible at larger $Q^2$. Comparisons with H1 data for dijet rates show good agreement under specific jet-cut schemes, illustrating the importance of virtual-photon structure and proper matching between direct and resolved processes for reliable predictions and potential impacts on $\alpha_s$ extractions. The results guide future jet measurements in the transition region and motivate higher-$E_T$ inclusive jet data to further constrain the interplay between direct and resolved contributions.
Abstract
We present next-to-leading order calculations of one- and two-jet production in eP collisions at HERA for photon virtualities in the range 1<Q^2<100 GeV^2. Soft and collinear singularities are extracted using the phase space slicing method. Numerical results are presented for HERA conditions with the Snowmass jet definition. The transition between photoproduction and deep-inelastic scattering is investigated in detail. We compare two approaches, the usual deep-inelastic theory, where the virtual photon couples only directly to quarks and antiquarks, and the photoproduction approach, where the photon couples either in the direct way or in the resolved way via the parton constituents of the virtual photon with the proton constituents. Finally we compare with recent H1 data of the dijet rate obtained for various photon virtualities Q^2 with special attention to the region, in which two jets have equal transverse momenta.