Neutralino/chargino pair production at NLO+NLL with resummation-improved PDFs for LHC Run II

TL;DR

This paper presents improved theoretical predictions for neutralino and chargino pair production at the LHC by incorporating threshold-resummation improved PDFs at NLO+NLL accuracy, reducing uncertainties and refining cross section estimates.

Contribution

It introduces the use of threshold-resummation improved PDFs in NLO+NLL calculations for supersymmetric particle production at the LHC, with a novel factorization method to reduce PDF uncertainties.

Findings

Resummation reduces scale uncertainties in cross section predictions.

Resummation contributions partially offset enhancements from matrix elements.

Updated predictions are relevant for ongoing LHC Run II searches.

Abstract

We make use of recently released parton density functions (PDFs) with threshold-resummation improvement to consistently calculate theoretical predictions for neutralino and chargino pair production at next-to-leading order and next-to-leading logarithmic accuracy. The updated cross sections have been computed for experimentally relevant higgsino and gaugino search channels at the ongoing Run II of the LHC. A factorisation method is applied to exploit the smaller PDF uncertainty of the global PDF sets and to avoid complications arising in the refitting of threshold-resummation improved PDF replicas in Mellin space. The reduction of the scale uncertainty due to the resummation is, however, explicitly taken into account. As expected, the resummation contributions in the PDF fits partially compensate the cross section enhancements induced by those in the partonic matrix elements.