Natural TeV-Scale Left-Right Seesaw for Neutrinos and Experimental Tests

Abstract

We present a TeV-scale left-right ultraviolet completion of type-I seesaw for neutrino masses based on the $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$ gauge group without parity, which leads to "large" light-heavy neutrino mixing while keeping the neutrino masses small in a natural manner guaranteed by discrete symmetries. We point out specific observable implications of this class of models if the $SU(2{)}_R$-breaking scale is of order 5 TeV, in searches for lepton flavor violating processes such as $\mu \to e\gamma$, $\mu \to 3e$ and $\mu -e$ conversion in nuclei, and lepton number violating processes such as neutrinoless double beta decay as well as at the LHC. In particular, if the upper limit on BR$(\mu \to e\gamma )$ improves by one order of magnitude, a large range of the parameters of the model would be ruled out.

Comments: 34 pages, 8 figures, 10 tables; some comments and references added; version accepted for publication in Phys. Rev. D