Identifying a Higgsino-like NLSP in the context of a keV-scale gravitino LSP

Abstract

The presence of a Higgsino-like neutralino next-to-lightest sparticle (NLSP) and a keV scale gravitino (G˜) LSP opens up new decay modes of the NLSP, mainly to a Higgs/Z boson and the LSP. Besides, a keV-scale gravitino as a warm dark matter candidate salvages a relatively-light Higgsino-like NLSP from dark matter constraints. We focus on the prospects of observing at least one b jet and two opposite sign leptons with a large missing transverse momenta (≥1b + ℓ+ℓ−+/ET) signal at the LHC. A distinguishing feature of this scenario is the production of longitudinal Z bosons in neutralino decays, unlike in the case of gauginolike neutralinos, where the Z is mostly transverse. The polarisation information of the parent Z boson gets reflected in the angular distributions of the decay leptons and in some other variables derived therefrom.