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We discuss a left-right (L-R) symmetric model with the double seesaw mechanism at the TeV scale generating Majorana masses for the active left-handed (LH) flavour neutrinos ν αL and the heavy right-handed (RH) neutrinos N βR , α, β = e, µ, τ , which in turn mediate lepton number violating processes, including neutrinoless double beta decay. The Higgs sector is composed of two Higgs doublets H L , H R and a bi-doublet Φ. The fermion sector has the usual for the L-R symmetric models quarks and leptons, along with three SU (2) singlet fermion S γL . The choice of bare Majorana mass term for these sterile fermions induces large Majorana masses for the heavy RH neutrinos leading to two sets of heavy Majorana particles N j and S k , j, k = 1, 2, 3, with masses m N j m S k . Working with a specific version of the model in which the ν αL − N βR and the N βR − S γL Dirac mass terms are diagonal, and assuming that m N j ∼ (1 − 1000) GeV and max(m S k ) ∼ (1 − 10) TeV, m N j m S k , we study in detail the new "non-standard" contributions to the 0νββ decay amplitude and half-life arising due to the exchange of virtual N j and S k . We find that in both cases of NO and IO light neutrino mass spectra, these contributions are strongly enhanced and are dominant at relatively small values of the lightest neutrino mass m 1(3) ∼ (10 −4 − 10 −2 ) eV over the light Majorana neutrino exchange contribution. In large part of the parameter space, the predictions of the model for the 0νββ decay generalised effective Majorana mass and half-life are within the sensitivity range of the planned next generation of neutrinoless double beta decay experiments LEGEND-200 (LEGEND-1000), nEXO, KamlAND-Zen-II, CUPID, NEXT-HD.

We explore an [Formula: see text] flavor-based left–right symmetric model where neutrino masses and mixing are explained through linear seesaw mechanism. Taking [Formula: see text] flavor symmetry and left–right gauge symmetry together and adding a low-scale seesaw mechanism gives the advantage of (a) getting diagonal structures for both charged lepton mass matrix and Dirac neutrino mass matrix, (b) simpler relations among neutrino observables in the model and (c) large light-heavy neutrino mixing which gives dominant contributions to various lepton flavor violating decays like [Formula: see text], [Formula: see text], [Formula: see text]. By saturating the experimental bounds on these decays we derive constraints on input model parameters and study analytically as well as numerically the correlation among model parameters and their dependence on experimentally determined neutrino parameters like [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]. We also study CP-violation via Jarlskog invariants and show extra contributions to CP-violating effects that the model generates due to unitarity violation in the neutrino sector.

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