Neutrinoless double beta decay in a left-right symmetric model with a double seesaw mechanism

We discuss a left-right (L-R) symmetric model with the double seesaw mechanism at TeV scale generating Majorana masses for active left-handed (LH) flavour neutrinos $\nu_{\alpha L}$ and heavy right-handed (RH) $N_{\beta R}$, $\alpha,\beta = e,\mu,\tau$, which in turn mediate lepton number violating processes, including neutrinoless beta decay. The Higgs sector is composed of two doublets $H_L$, $H_R$, bi-doublet $\Phi$. fermion has usual L-R models quarks leptons, along three $SU(2)$ singlet $S_{\gamma L}$. choice bare mass term these sterile fermions induces large RH leading to sets particles $N_j$ $S_k$, $j,k=1,2,3$, $m_{N_j} \ll m_{S_k}$. Working specific version L} - N_{\beta R}$ R} S_{\gamma Dirac terms are diagonal, assuming that \sim (1 1000)$ GeV ${\rm max}(m_{S_k}) 10)$ TeV, m_{S_k}$, we study detail new ``non-standard'' contributions $0\nu\beta\beta$ decay amplitude half-life arising due exchange virtual $S_k$. find both cases NO IO light neutrino spectra, strongly enhanced dominant relatively small values lightest $m_{1(3)} (10^{-4} 10^{-2})$ eV over contribution. In part parameter space, predictions generalised effective within sensitivity range planned next generation experiments LEGEND-200 (LEGEND-1000), nEXO, KamlAND-Zen-II, CUPID, NEXT-HD.