in this case arises entirely from $M_\nu^D$ and $M_R$ similar to type-I seesaw mechanism: $$M_{\nu}=-{M^D_{\nu}}^T {M^R_{\nu}}^{-1} {M^D_{\nu}}.
\label{t1}$$

This gave us the correct experimentally observed masses and mixings for the light neutrino and hence this is the approach we have chosen for the neutrino sector [^2].

![Right-handed neutrino masses as a function of $\lambda'_R$ for minimal charged Higgs mixing.[]{data-label="fig:rhneumass"}](rh_neutrino_mass2.png){height="3.0in" width="3.50in"}

The right-handed neutrino masses in this scenario are generated at one loop and proportional to the square of the charged lepton Yukawa coupling $\tilde{Y}_l$. Therefore, right handed neutrino masses are quite small. As the other Yukawa coupling $Y_l$ is responsible for generating Dirac masses for the neutrinos, it is orders of magnitude smaller than $\tilde{Y}_l$ and hence does not have any impact on right-handed neutrino masses. We show the variation of the three right-handed neutrino masses $M_{N_{1,2,3}}$ with the Yukawa coupling $\lambda^{\prime}_R$ in Fig. \[fig:rhneumass\]. As can be seen, that for $\lambda^{\prime}_R \sim 0.1-1$, the lightest right handed neutrino mass $M_{N_1}$ varies from $3 \, \rm{eV}-30$ eV, while $M_{N_{2,3}}$ are in the sub-MeV scale. In deriving this, we utilize Eq. \[RHM\], where we diagonalize the right-handed Majorana mass matrix $M_\nu^R$. The charged Higgs boson masses and mixings used to obtain 