  In a recent Letter 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 offer some
missing technical details. We also carefully analyze the physically appealing
possibility of 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.
