Revisiting the Exclusion Limits from Direct Chargino-Neutralino Production at the LHC

TL;DR

This paper reevaluates LHC limits on gaugino masses in SUSY models, considering more realistic decay scenarios, and finds that three-body decays can lead to more stringent bounds than traditional two-body decay assumptions.

Contribution

It assesses the impact of realistic decay modes on existing gaugino mass exclusion limits, highlighting the significance of three-body decay channels in setting more severe bounds.

Findings

Three-body decay modes can tighten exclusion bounds.

Realistic branching ratios significantly affect mass limits.

Validation of ATLAS limits across multiple final states.

Abstract

We revisit the existing limits on the gaugino masses in various Supersymmetric (SUSY) scenarios derived from Run-I data of the LHC. These limits obtained from the various final states rely heavily on the simplified assumptions regarding the masses, compositions and decay branching ratios of the gauginos. The most promising exclusion limits on the gaugino masses are obtained from trilepton final states while the second lightest neutralino ($\widetilde \chi_2^0$) decaying into the SM-like Higgs and lightest SUSY particle (LSP) results in the weakest bounds. Our aim is to assess the extent of deviation of these exclusion limits in more realistic scenarios. After a brief discussion on the various decay modes of the $\widetilde \chi_2^0$ and the lightest chargino ($\widetilde \chi^{\pm}_1$), we proceed to validate the ATLAS exclusion limits obtained from trilepton, $l\gamma\gamma$ and $lb\bar b$ final states associated with missing energy. We then consider different combinations of the relevant branching ratios to study their impact on the existing bounds. The results are presented alongside the existing exclusion limits to showcase the extent of the obtained deviation. We also observe that the three-body decay modes of $\widetilde \chi_2^0$ and $\widetilde \chi^{\pm}_1$ via off-shell slepton decays resulting in trilepton final states provide bounds that are far more severe in some parts of the available parameter space than that obtained from the usual two-body decay modes of the aforementioned gauginos.