Speaker
Description
We present a detailed discussion on neutrinoless double beta decay within
a class of left-right symmetric models where neutrino mass originates by natural type II
seesaw dominance. The spontaneous symmetry breaking is implemented with doublets,
triplets and bidoublet scalars. The fermion sector is extended with an extra sterile neutrino
per generation that helps in implementing the seesaw mechanism. The presence of extra
particles in the model exactly cancels type-I seesaw and allows large value for Dirac neutrino
mass matrix $M_D$ . The key feature of this work is that all the physical masses and mixing
are expressed in terms of neutrino oscillation parameters and lightest neutrino mass thereby
facilitating to constrain light neutrino masses from neutrinoless double beta decay. With this large value of
$M_D$ new contributions arise due to; i) purely left-handed current via exchange of heavy
right-handed neutrinos as well as sterile neutrinos, ii) the so called $\lambda$ and $\eta$ diagrams. New
physics contributions also arise from right-handed currents with right-handed gauge boson
$W_R$ mass around 3 TeV. From the numerical study, we find that the new contributions to
neutrinoless double beta decay not only saturate the current experimental bound but also give lower limit on absolute scale of lightest neutrino mass and shows NH pattern of mass hierarchy is favorable..
Summary
The seesaw mechanisms that explain light neutrino masses require them to be
Majorana particles which violates lepton number by two units. This lepton number
violation can be observed at Large Hadron Collider through same-sign dilepton events and at low energy experiments by the rare process like neutrinoless double beta decay provided the seesaw scale is low. The canonical seesaw mechanism requires the existence of SM gauge-singlet sterile neutrinos at very high energy scales which can not be accessible to any experiment in foreseeable future. Therefore, it is essential to explore alternative
low scale seesaw mechanisms which offer direct testability at the LHC and other low-energy experiments. We propose a new framework where the new physics contributions can be expressed
in terms of neutrino oscillation parameters. One important aspect of this framework is that
one can get lower bound on abosolute scale of lightest neutrino mass and mass hierarchy
by analyzing the new physics contributions to neutrinoless double beta decay. We also interlink neutrinoless double beta decay with cosmology, beta decay and neutrino oscillation.
