Closing in on compressed gluino-neutralino spectra at the LHC

TL;DR

This paper investigates the potential to detect compressed gluino-neutralino spectra at the LHC by recasting existing searches and proposing a new multijet strategy, focusing on the radiative gluino decay channel which is sensitive to small mass differences.

Contribution

It introduces a dedicated search strategy for compressed spectra and demonstrates the effectiveness of multijet searches over monojet in this context.

Findings

Recasting of Run I searches constrains radiative gluino decay in compressed spectra.

A new multijet search strategy shows higher sensitivity than monojet approaches.

Potential for improved detection of small mass splittings at LHC Run II.

Abstract

A huge swath of parameter space in the context of the Minimal Supersymmetric Standard Model (MSSM) has been ruled at after run I of the LHC. Various exclusion contours in the $m_{\tilde{g}}-\m_{\tilde{\chi}_{1}^{0}}$ plane were derived by the experimental collaborations, all based on three-body gluino decay topologies. These limits are however extremely model dependent and do not always reflect the level of exclusion. If the gluino-neutralino spectrum is compressed, then the current mass limits can be drastically reduced. In such situations, the radiative decay of the gluino $\gino \ra g \neut{1}$ can be dominant and used as a sensitive probe of small mass splittings. We examine the sensitivity of constraints of some Run I experimental searches on this decay after recasting them within the \texttt{MadAnalysis5} framework. The recasted searches are now part of the \texttt{MadAnalysis5} Public Analysis Database. We also design a dedicated search strategy and investigate its prospects to uncover this decay mode of the gluino at run II of the LHC. We emphasize that a multijet search strategy may be more sensitive than a monojet one, even in the case of very small mass differences.