Neutrino Mass and Neutrinoless double beta decay in SO(10) GUT with Pati-Salam symmetry

TL;DR

This paper explores a non-supersymmetric SO(10) GUT model with specific intermediate symmetries, analyzing gauge coupling unification, neutrino mass generation via extended seesaw, and implications for neutrinoless double beta decay and collider searches.

Contribution

It introduces a novel SO(10) GUT framework with asymmetric intermediate symmetries, incorporating an extended seesaw mechanism and detailed predictions for neutrinoless double beta decay.

Findings

Successful gauge coupling unification within proton decay constraints

Predictions for effective Majorana mass parameter and half-life in neutrinoless double beta decay

Lower bound on lightest neutrino mass derived from experimental bounds

Abstract

We demonstrate how a class of non-supersymmetric $SO(10)$ GUT with asymmetric left-right theory $SU(2)_L \times U(1)_R \times U(1)_{B-L} \times SU(3)_C$ and Pati-Salam theory $SU(2)_L \times SU(2)_R \times SU(4)_C$ as intermediate symmetry breaking steps leads to successful gauge coupling unification satisfying proton decay constraints. The motivation behind this work is two fold: firstly to study the renormalization group evolution equations for gauge couplings by keeping right-handed neutral gauge boson $Z_R$ around LHC energy range leading interesting dilepton searches at collider while fixing charge partner of the gauge boson $W_R$ at very high scale; secondly to explain neutrino masses and associated lepton number violating process like neutrinoless double beta decay in three possible cases depending on how $SU(2)_L \times U(1)_R \times U(1)_{B-L} \times SU(3)_C$ breaks down to SM. We include one extra fermion singlet per generation in order to implement gauged extended seesaw where light neutrino mass is governed by natural type-II seesaw mechanism whereas type-I seesaw contribution is exactly canceled out. Since light neutrino mass formula is independent of Dirac neutrino mass matrix, the value of Dirac neutrino mass is taken to be up-type quark mass matrix which is a characteristics of Pati-Salam symmetry relating quarks with leptons. We present analytic relation for effective Majorana mass parameter and corresponding half-life arising from new physics contributions due to purely left-handed currents through exchange of heavy right-handed neutrinos and sterile neutrinos. We numerically estimate effective Majorana mass parameter and half-life vs. lightest neutrino mass and derive lower bound on lightest neutrino mass by saturating with experimental bounds like GERDA Phase-II, KamLANDZen and EXO.