Sterile Neutrino Portal Dark Matter from Semi-Production

Abstract

In this paper, we study the feeble sterile neutrino portal dark matter under the $Z_3$ symmetry. The dark sector consists of one fermion singlet $\ddot{I}‡$ and one scalar singlet $\ddot{I}‡$, which transforms as $\ddot{I}‡\to e^{i2\ddot{I}€/3}\ddot{I}‡,\ddot{I}•\to e^{i2\ddot{I}€/3}\ddot{I}•$ under the $Z_3$ symmetry. Regarding fermion singlet $\ddot{I}‡$ as the dark matter candidate, the new interaction terms $y_{\ddot{I}}‡\ddot{I}•\overline{\ddot{I}{‡}^c}\ddot{I}‡$ and $\hat{I}¼\ddot{I}{•}^3/2$ could induce various new production channels. For instance, when $m_{\ddot{I}}•>2m_{\ddot{I}}‡$, the pair decay $\ddot{I}•\to \ddot{I}‡\ddot{I}‡$ could be the dominant channel, rather than the delayed decay $\ddot{I}•\to \ddot{I}‡\hat{I}½$. Another appealing scenario is when the dark sector is initially produced through the scattering process as $NN\to \ddot{I}‡\ddot{I}‡,NN\to \ddot{I}•\ddot{I}•,h\hat{I}½\to \ddot{I}‡\ddot{I}•$, then the semi-production processes $N\ddot{I}‡\to \ddot{I}•\ddot{I}•,N\ddot{I}•\to \ddot{I}•\ddot{I}‡,N\ddot{I}‡\to \ddot{I}‡\ddot{I}‡$ could lead to the exponential growth of dark sector abundances. The phenomenology of sterile neutrino and the cosmological impact of the dark scalar are also considered in the $Z_3$ symmetric model.

24 pages, 9 figures