Multi-jet Phenomenology for Hadron Colliders in the High Energy Limit

We have incorporated next-to-leading logarithmic corrections into the High Energy Jets (HEJ) formalism and parton-level Monte Carlo generator for plus inclusive dijet production. This has involved an analytic demonstration of factorisation for the relevant configurations, an extraction of the effective current and proof of its gauge invariance. We have thoroughly validated our numerical implementation and matching of the cross section to leading order accuracy. We have studied the impact of these corrections upon transverse momentum distributions and found a significant improvement in the description of data. We also present a new merging algorithm, inspired by the CKKW-L method, for combining high energy and soft-collinear logarithms. This has been implemented for HEJ+. Multiple parton interactions and hadronisation effects are also accounted for, allowing for an accurate description of jets shapes. We find good agreement with data for observables such as the average number of jets and gap fractions which are relevant for understanding the impact of jet vetoes.