Abstract
Several important processes and analyses at the LHC are sensitive to higher-order perturbative corrections beyond what can currently be calculated at fixed order. The formalism of High Energy Jets (HEJ) calculates the corrections systematically enhanced for a large ratio of the centre-of-mass energy to the transverse momentum of the observed jets. These effects are relevant in the analysis of e.g. Higgs-boson production in association with dijets within the cuts devised to enhance the contribution from Vector Boson Fusion (VBF).HEJ obtains an all-order approximation, based on logarithmic corrections which are matched to fixed-order results in the cases where these can be readily evaluated. In this paper we present an improved framework for the matching utilised in HEJ, which for merging of tree-level results is mathematically equivalent to the one used so far. However, by starting from events generated at fixed order and supplementing these with the all-order summation, it is computationally simpler to obtain matching to calculations of high multiplicity.We demonstrate that the impact of the higher-multiplicity matching on predictions is small for the gluon-fusion (GF) contribution of Higgs-boson production in association with dijets in the VBF-region, so perturbative stability against high-multiplicity matching has been achieved within HEJ. We match the improved HEJ prediction to the inclusive next-to-leading order (NLO) cross section and compare to pure NLO in the h → γγ channel with standard VBF cuts.
Highlights
High Energy Jets (HEJ) obtains an all-order approximation, based on logarithmic corrections which are matched to fixed-order results in the cases where these can be readily evaluated
We demonstrate that the impact of the higher-multiplicity matching on predictions is small for the gluon-fusion (GF) contribution of Higgs-boson production in association with dijets in the Vector Boson Fusion (VBF)-region, so perturbative stability against high-multiplicity matching has been achieved within HEJ
The scale-variation of the normalisation of the cross sections is determined by the treelevel matrix elements, and mostly unchanged by the leading logarithmic (LL) high-energy resummation implemented in HEJ
Summary
In order to match each m-jet rate to tree-level accuracy, each generated event in the all-order phase-space is mapped to a m-jet tree-level kinematic point, and requires an evaluation of the full m-jet matrix element. The scale-variation of the normalisation of the cross sections is determined by the treelevel matrix elements, and mostly unchanged by the leading logarithmic (LL) high-energy resummation implemented in HEJ. This could be reduced by extending the reweighting factor wm−jet to next-to-leading order accuracy. In order to do this, one would have to integrate over all m+1 parton real emission phase space resulting in a specific m-jet Born level kinematics. This in turn allows for matching to higher multiplicity for a given CPU envelope
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