We study the properties of the right-handed sneutrino and its viability as a WIMP dark matter candidate in an extended version of the NMSSM in which a right-handed neutrino superfield is included with a coupling to the singlet Higgs in order to provide non-vanishing Majorana neutrino masses. We perform a systematic study of the parameter space, including LEP constraints and experimental bounds on low-energy observables. We investigate the conditions under which the right-handed sneutrino has the correct relic abundance and the dominant annihilation channels. Next we calculate the theoretical predictions for the sneutrino-proton elastic scattering cross section and compare it with present and future experimental sensitivities. We find that sneutrinos with a mass in the range of 5-200 GeV can reproduce the observed dark matter relic density without being excluded by direct dark matter searches and for natural values of the input parameters. Interestingly, the predicted scattering cross section is generally within the reach of future experiments. Finally, we comment on the possible implications for collider physics.

LaTeX, 59 pages, 20 figures