Forward Jet Production in Deep Inelastic Scattering at HERA

TL;DR

This paper measures the forward jet cross section in deep inelastic scattering at HERA to investigate BFKL-like effects, finding an excess at small Bjorken-x not explained by DGLAP-based models but consistent with the Colour Dipole model.

Contribution

It provides the first detailed comparison of forward jet production data with BFKL and DGLAP evolution models, highlighting the limitations of DGLAP in this regime.

Findings

Observed excess of forward jets at small x_bj not matched by DGLAP models

Colour Dipole model describes the data reasonably well

Results support the presence of BFKL-like effects in forward jet production

Abstract

The inclusive forward jet cross section in deep inelastic $e^+p$ scattering has been measured in the region of $x$--Bjorken, ~$4.5 \cdot 10^{-4}$~ to ~$4.5 \cdot 10^{-2}$. This measurement is motivated by the search for effects of BFKL--like parton shower evolution. The cross section at hadron level as a function of \xbj is compared to cross sections predicted by various Monte Carlo models. An excess of forward jet production at small \xbj is observed, which is not reproduced by models based on DGLAP parton shower evolution. The Colour Dipole model describes the data reasonably well. Predictions of perturbative QCD calculations at the parton level based on BFKL and DGLAP parton evolution are discussed in the context of this measurement.