Right-handed sneutrino dark matter in $\mathbf{U}(1{)}^{\prime }$ seesaw models and its signatures at the LHC

Abstract

We suggest a real right-handed sneutrino, ${\tilde{N}}_1$, as a good dark matter candidate in a supersymmetric $Z^{\prime }$ model realizing the seesaw mechanism. When the extra gaugino, ${\tilde{Z}}^{\prime }$, is lighter than $Z^{\prime }$, the thermal freeze-out of the dark matter annihilation to right-handed neutrinos, ${\tilde{N}}_1{\tilde{N}}_1\to NN$, 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 $pp\to {\tilde{Z}}^{\prime }{\tilde{Z}}^{\prime }\to NN+\text{ptmiss}$ as ${\tilde{Z}}^{\prime }$ can be copiously produced from the cascade decays of gluinos/squarks, which is complementary to the search of $pp\to Z^{\prime }\to NN$. This may also open up a promising new channel of finding the Higgs boson from the displaced $N$ decay.

Comments: 1+24 pages, 15 figures. v2: minor improvements, typos fixed, updated references, version published in JHEP