Gravitino Dark Matter with Weak-Scale Right-Handed Sneutrino

Understand

We consider cosmological implications of supersymmetric models with right-handed (s)neutrinos where the neutrino masses are purely Dirac-type.

• We pay particular attention to the case where gravitino is the lightest superparticle while one of the right-handed sneutrinos is next-to-the-lightest superparticle.
• We study constraints from big-bang nuleosynthesis and show that the constraints could be relaxed compared to the case without right-handed sneutrinos.
• As a result, the gravitino-dark-matter scenario becomes viable with relatively large value of the gravitino mass.