Disentangling the seesaw mechanism in the minimal left-right symmetric model

Abstract

In a recent paper we presented a systematic way of testing the seesaw origin of neutrino mass in the context of the minimal left-right symmetric model. The essence of the program is to exploit lepton number violating decays of doubly charged scalars, particles which lie at the heart of the Higgs-mechanism-based seesaw, to probe the Dirac neutrino mass term which in turn enters directly into a number of physical processes including the decays of right-handed neutrinos into the W boson and left-handed charged leptons. In this longer version we discuss at length these and related processes, and we offer some missing technical details. We also carefully analyze the physically appealing possibility of a parity conserving Yukawa sector showing that the neutrino Dirac mass matrix can be analytically expressed as a function of light and heavy neutrino masses and mixing, without resorting to any additional discrete symmetries, a context in which the seesaw mechanism can be disentangled completely. When parity does get broken, we show that, in the general case, only the Hermitian part of the Dirac mass term is independent which substantially simplifies the task of testing experimentally the origin of neutrino mass. We illustrate this program through some physical examples that allow simple analytical expressions. Our work shows that the minimal left-right symmetric model is a self-contained theory of neutrino mass which can be in principle tested at the LHC or the next hadron collider.