Scalar leptoquark pair production at the LHC: precision predictions in the era of flavour anomalies

TL;DR

This paper provides the most precise theoretical predictions for scalar leptoquark pair production at the LHC, including next-to-next-to-leading logarithmic resummation and t-channel effects relevant for flavour anomaly explanations.

Contribution

It introduces a comprehensive calculation of leptoquark pair production incorporating t-channel diagrams, NNLL resummation, and provides public tools for model-specific predictions.

Findings

Cross section corrections up to 60% for some scenarios.

Interplay between t-channel contributions, Yukawa couplings, and leptoquark properties.

Predictions are highly scenario-dependent, requiring dedicated calculations.

Abstract

We comprehensively examine precision predictions for scalar leptoquark pair production at the LHC. In particular, we investigate the impact of lepton $t$-channel exchange diagrams that are potentially relevant in the context of leptoquark scenarios providing an explanation for the flavour anomalies. We also evaluate the corresponding total rates at the next-to-leading order in QCD. Moreover, we complement this calculation with the resummation of soft-gluon radiation at the next-to-next-to-leading logarithmic accuracy, hence providing the most precise predictions for leptoquark pair production at the LHC to date. Relying on a variety of benchmark scenarios favoured by the anomalies, our results exhibit an interesting interplay between the $t$-channel diagram contributions, the flavour texture satisfied by the leptoquark Yukawa couplings, the leptoquark masses and their representations under the Standard Model gauge group, as well as the chosen set of parton densities used for the numerical evaluations. The net effect on a cross section turns out to be very non-generic and ranges up to about 60% with respect to the usual next-to-leading-order predictions in QCD (i.e. without any $t$-channel contribution) for some scenarios considered. Dedicated calculations are thus required for any individual leptoquark model that could be considered in a collider analysis in order to assess the size of the studied corrections. In order to facilitate such calculations we provide dedicated public numerical packages.