Effects of Planck Scale Physics on Neutrino Mixing Parameters in Left-Right Symmetric Models

TL;DR

This paper investigates how Planck scale physics, through higher-dimensional operators, can significantly alter neutrino mixing predictions in Left-Right Symmetric Models, especially at symmetry breaking scales below 10^{14} GeV.

Contribution

It introduces the impact of Planck scale suppressed operators on neutrino parameters within LRSM, highlighting potential deviations from tree-level seesaw predictions.

Findings

Planck scale effects can modify neutrino mixing angles.

Significant changes occur if left-right symmetry breaks below 10^{14} GeV.

Dimension five operators can arise in SO(10) GUT contexts.

Abstract

Left right symmetric models (LRSM) are extensions of the standard model by an enlarged gauge group $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ where automatic inclusion of right handed fermions as $SU(2)_R$ doublets guarantees a natural seesaw origin of neutrino masses. Apart from the extended gauge symmetry, LRSM also has an in-built global discrete symmetry, called D-parity which ensures equal gauge couplings for left and right sectors. Motivated by the fact that global symmetries are expected to be explicitly broken by theories of quantum gravity, here we study the effects of such gravity or Planck scale physics on neutrino masses and mixings by introducing explict D-parity breaking Planck scale suppressed higher dimensional operators. Although such Planck scale suppressd operators have dimension at least six in generic LRSM, dimension five operators can also arise in the presence of additional scalar fields which can be naturally accommodated within SO(10) grand unified theory (GUT) multiplets. We show that, such corrections can give rise to significant changes in the predictions for neutrino mixing parameters from the ones predicted by tree level seesaw formula if the left right symmetry breaking scale is lower than $10^{14}$ GeV.