A very heavy sneutrino as viable thermal dark matter candidate in U(1)′ extensions of the MSSM

Abstract We study the Standard Model singlet (“right-handed”) sneutrino ν ˜ R $$ {\tilde{\nu}}_R $$ dark matter in a class of U(1)′ extensions of the MSSM that originate from the breaking of the E 6 gauge group. These models, which are referred to as UMSSM, contain three right-handed neutrino superfields plus an extra gauge boson Z′ and an additional SM singlet Higgs with mass ≃ M Z ′, together with their superpartners. In the UMSSM the right sneutrino is charged under the extra U(1)′ gauge symmetry; it can therefore annihilate via gauge interactions. In particular, for M ν ˜ R ≃ M Z ′ / 2 $$ {M}_{{\tilde{\nu}}_R}\simeq {M}_{Z\prime }/2 $$ the sneutrinos can annihilate by the exchange of (nearly) on-shell gauge or Higgs bosons. We focus on this region of parameter space. For some charge assignment we find viable thermal ν ˜ R $$ {\tilde{\nu}}_R $$ dark matter for mass up to ∼ 43 TeV. This is the highest mass of a good thermal dark matter candidate in standard cosmology that has so far been found in an explicit model. Our result can also be applied to other models of spin−0 dark matter candidates annihilating through the resonant exchange of a scalar particle. These models cannot be tested at the LHC, nor in present or near-future direct detection experiments, but could lead to visible indirect detection signals in future Cherenkov telescopes