Neutralino-chargino pair production at NLO+NLL with resummation-improved parton density functions for LHC Run II

J Fiaschi,M Klasen

doi:10.1103/physrevd.98.055014

J Fiaschi, M Klasen

Open Access

https://doi.org/10.1103/physrevd.98.055014

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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.

Highlights

The minimal supersymmetric standard model (MSSM) is a theoretically and phenomenologically well-motivated extension of the Standard Model (SM) of particle physics [1,2]
For positive chargino production, the introduction of the new resummed parton density functions (PDFs) set further increases the cross section by about 1.5% at low electroweakinos masses and of about 0.5% at higher masses. This effect is partially compensated by the effect of the resummation in the partonic matrix elements, such that in the end we observe a positive correction to the fixed-order next-to-leading order (NLO) cross section obtained from the global PDF set of less than 1% for light Higgsino masses and a negative correction of less than 0.5% for heavier masses
We have studied the effects of the introduction of threshold-resummation improved PDF sets in consistent NLO þ next-to-leading logarithmic (NLL) calculations for the associated production of neutralinos and charginos at Run II of the LHC

Summary

Introduction

The minimal supersymmetric standard model (MSSM) is a theoretically and phenomenologically well-motivated extension of the Standard Model (SM) of particle physics [1,2]. It predicts, in particular, fermionic partners of the neutral and charged gauge and Higgs bosons called gauginos and Higgsinos, whose lightest neutral mass eigenstate, the lightest neutralino, is one of the best studied dark matter candidates [3,4,5,6]. Searches for gaugino- [7,8] or Higgsino-like particles [9,10] are important physics goals at the LHC They are often carried out in the framework of simplified models [11,12]. Be taken that the theoretical assumptions are not overly simplified [13]

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