Impact on the light Higgsino-LSP scenario from physics beyond the minimal supersymmetric standard model

The modest addition of the dimension-5 term λ (over(H, ̂)_u ṡ over(H, ̂)_d)² / M to the superpotential of the minimal supersymmetric standard model (MSSM) originated from physics beyond the MSSM (BMSSM) has a significant impact on the scenario of the Higgsino-dominated neutralino state being the lightest supersymmetric particle (LSP). It increases the mass difference between the LSP and the lighter chargino as well as that between the LSP and the second-lightest neutralino. This enhances the LHC discovery potential of the chargino and neutralino decays, producing more energetic charged leptons or pions than the decays without the BMSSM corrections. Furthermore, the coannihilation between the lighter chargino or second-lightest neutralino and the LSP is reduced substantially such that the LSP mass does not have to be very heavy. Consequently, an almost pure Higgsino LSP with its mass ∼ 100 GeV in the BMSSM can account for all the relic density of cold dark matter in the Universe unless tan β is too large.