  Motivated by grand unification considerations, we analyze a simple extension
of the minimal supersymmetric standard model with additional pairs of
vector-like chiral supermultiplets. We focus on the so-called LND setup, which
enlarges the particle content of the minimal model by two vector-like pairs of
weak doublets (one pair of leptons and one pair of down-type quarks) and one
vector-like pair of neutrino singlets. Imposing collider and low-energy
constraints, sneutrinos and neutralinos both emerge as possible lightest
supersymmetric particles and thus dark matter candidates. We perform a complete
analysis of the dark sector and study the viability of these neutralino and
sneutrino dark matter options. We show that cosmological considerations (the
dark matter relic abundance and its direct and indirect detection signals)
restrict neutralino dark matter to exhibit similar properties as in the minimal
supersymmetric standard model, and impose the sneutrino dark matter candidate
to be singlet-like, rather than doublet-like. Allowing the mixing of the
fermionic component of the new supermultiplets with the Standard Model third
generation fermions, we moreover demonstrate the existence of collider signals
that are distinguishable from other, more minimal, supersymmetric scenarios by
virtue of an enhanced production of events enriched in tau leptons. We
furthermore show that this signature yields robust LHC signals, that could
potentially be differentiated from the background in future data.
