Right-handed sneutrino dark matter in U(1)′ seesaw models and its signatures at the LHC

Abstract

We suggest a real right-handed sneutrino, Ñ ₁, as a good dark matter candidate in a supersymmetric Z′ model realizing the seesaw mechanism. When the extra gaugino, ${\tilde{Z}^{\prime}}$, is lighter than Z′, the thermal freeze-out of the dark matter annihilation to right-handed neutrinos, Ñ ₁ Ñ ₁ → NN, through the t-channel ${\tilde{Z}^{\prime}}$ exchange is shown to produce the right dark matter density. It is essential to include the decay and inverse decay of N in this process, otherwise N decouples too early and thus dark matter is overproduced. At the LHC, the search for the seesaw mechanism can be made by observing the signatures of $pp \to {\tilde{Z}^{\prime}}{\tilde{Z}^{\prime}} \to NN$ + as ${\tilde{Z}^{\prime}}$ can be copiously produced from the cascade decays of gluinos/squarks,which is complementary tothesearch of pp → Z′ → NN. This may also open up a promising new channel of finding the Higgs boson from the displaced N decay.