Direct Chargino-Neutralino Production at the LHC: Interpreting the Exclusion Limits in the Complex MSSM

TL;DR

This paper reevaluates LHC exclusion limits on supersymmetric chargino-neutralino production within the complex MSSM, highlighting the impact of decay modes and parameter variations on the excluded regions, using full NLO calculations.

Contribution

It provides a comprehensive analysis of how realistic decay modes and parameter dependencies affect LHC exclusion limits in the MSSM, incorporating full NLO calculations.

Findings

Decay mode neu2->neu1 h reduces excluded parameter space.

Exclusion limits are sensitive to M_1 phase, tau mass, tan beta, and sfermion masses.

NLO calculations significantly influence the bounds and future LHC reach.

Abstract

We re-assess the exclusion limits on the parameters describing the supersymmetric (SUSY) electroweak sector of the MSSM obtained from the search for direct chargino-neutralino production at the LHC. We start from published limits obtained in simplified models, where for the case of heavy sleptons the relevant branching ratio, BR(neu2->neu1 Z), is set to one. We show how the decay mode neu2->neu1 h, which cannot be neglected in any realistic model once kinematically allowed, substantially reduces the excluded parameter region. We analyze the dependence of the excluded regions on the phase of the gaugino soft SUSY-breaking mass parameter, M_1, on the mass of the light scalar tau, on tb as well as on the squark and slepton mass scales. Large reductions in the ranges of parameters excluded can be observed in all scenarios. The branching ratios of charginos and neutralinos are evaluated using a full NLO calculation for the complex MSSM. The size of the effects of the NLO calculation on the exclusion bounds is investigated. We furthermore assess the potential reach of the experimental analyses after collecting 100/fb at the LHC running at 13 TeV.