Strong CP Problem, Neutrino Masses and the 750 GeV Diphoton Resonance

TL;DR

This paper proposes a left-right symmetric model that addresses the strong CP problem without axions, explains the 750 GeV diphoton resonance, and links neutrino masses to neutrinoless double beta decay via right-handed currents.

Contribution

It introduces a novel left-right symmetric framework that simultaneously solves the strong CP problem, accounts for the 750 GeV diphoton excess, and relates neutrino mass structures to neutrinoless double beta decay.

Findings

The model naturally suppresses Dirac neutrino masses at two loops.

It provides a quantitative analysis of neutrinoless double beta decay.

The framework explains the 750 GeV diphoton resonance observed at the LHC.

Abstract

We present an $SU(3)^{}_{c}\times SU(2)^{}_{L}\times SU(2)^{}_{R}\times U(1)_{L}^{}\times U(1)_{R}^{}\rightarrow SU(3)^{}_{c}\times SU(2)^{}_{L}\times SU(2)^{}_{R}\times U(1)^{}_{B-L}$ left-right symmetric model with a discrete parity symmetry to realize a universal seesaw scenario. The model can simultaneously solve the strong CP problem without resorting to the unobserved axion and explain the 750 GeV diphoton resonance reported recently by the ATLAS and CMS collaborations at the LHC. Owing to large suppressions in the two-loop induced Dirac mass terms, the Majorana mass matrices of left- and right-handed neutrinos naturally share the same structure. That allows us to quantitatively study the neutrinoless double beta decay induced by the right-handed currents.