In supersymmetric theories like the Next-to-Minimal Supersymmetric Standard
Model (NMSSM), the lightest neutralino with bino or singlino as its dominant
component is customarily taken as dark matter (DM) candidate. Since light
Higgsinos favored by naturalness can strength the couplings of the DM and thus
enhance the DM-nucleon scattering rate, the tension between naturalness and DM
direct detection results becomes more and more acute with the improved
experimental sensitivity. In this work, we extend the NMSSM by inverse seesaw
mechanism to generate neutrino mass, and show that in certain parameter space
the lightest sneutrino may act as a viable DM candidate, i.e. it can annihilate
by multi-channels to get correct relic density and meanwhile satisfy all
experimental constraints. The most striking feature of the extension is that
the DM-nucleon scattering rate can be naturally below its current experimental
bounds regardless of the higgsino mass, and hence it alleviates the tension
between naturalness and DM experiments. Other interesting features include that
the Higgs phenomenology becomes much richer than that of the original NMSSM due
to the relaxed constraints from DM physics and also due to the presence of
extra neutrinos, and that the signatures of sparticles at colliders are quite
different from those with neutralino as DM candidate.Comment: 33 page
