Forward Jet and Particle Production at HERA

TL;DR

This paper investigates forward jet and particle production in deep inelastic scattering at HERA, comparing experimental data with QCD predictions to understand the evolution effects at low Bjorken-x.

Contribution

It provides detailed measurements of forward jets and particles, and evaluates the validity of different QCD evolution models against the data.

Findings

DGLAP-based predictions largely fail to describe the data

Resolved photon contributions improve DGLAP predictions

BFKL and CCFM models are compared to experimental results

Abstract

Single particles and jets in deeply inelastic scattering at low x are measured with the H1 detector in the region away from the current jet and towards the proton remnant, known as the forward region. Hadronic final state measurements in this region are expected to be particularly sensitive to QCD evolution effects. Jet cross-sections are presented as a function of Bjorken-x for forward jets produced with a polar angle to the proton direction, theta, in the range 7 < theta < 20 degrees. Azimuthal correlations are studied between the forward jet and the scattered lepton. Charged and neutral single particle production in the forward region are measured as a function of Bjorken-x, in the range 5 < theta < 25 degrees, for particle transverse momenta larger than 1 GeV. QCD based Monte Carlo predictions and analytical calculations based on BFKL, CCFM and DGLAP evolution are compared to the data. Predictions based on the DGLAP approach fail to describe the data, except for those which allow for a resolved photon contribution.