Sneutrino Hybrid Inflation

We review the scenario of sneutrino hybrid inflation, where one of the singlet sneutrinos, the superpartners of the right-handed neutrinos, plays the role of the inflaton. In a minimal model of sneutrino hybrid inflation, the spectral index is given by $n_s \approx 1 + 2 \gamma$. With $\gamma = 0.025 \pm 0.01$ constrained by WMAP, a running spectral index $|d n_s/d \ln k| \ll |\gamma|$ and a tensor-to-scalar ratio $r \ll \gamma^2$ are predicted. Small neutrino masses arise from the seesaw mechanism, with heavy masses for the singlet (s)neutrinos generated by the vacuum expectation value of the waterfall field after inflation. The baryon asymmetry of the universe can be explained by non-thermal leptogenesis via sneutrino inflaton decay, with low reheat temperature $T_RH \approx 10^6$ GeV.