# Higgs Parity Grand Unification

## TL;DR

This paper proposes a grand unification scheme based on Higgs Parity and $SO(10)$ symmetry, explaining the Higgs quartic coupling behavior, achieving precise gauge coupling unification, and predicting neutrino properties and other parameters.

## Contribution

It introduces a new $SO(10)$-based unification model with Higgs Parity, providing precise parameter predictions and a consistent explanation for fermion masses and mixing.

## Key findings

- Predicts QCD coupling constant to 1% accuracy.
- Achieves top quark mass prediction accuracy of 0.2%.
- Suggests a normal neutrino mass hierarchy.

## Abstract

The vanishing of the Higgs quartic coupling of the Standard Model at high energies may be explained by spontaneous breaking of Higgs Parity. Taking Higgs Parity to originate from the Left-Right symmetry of the $SO(10)$ gauge group, leads to a new scheme for precision gauge coupling unification that is consistent with proton decay. We compute the relevant running of couplings and threshold corrections to allow a precise correlation among Standard Model parameters. The scheme has a built-in solution for obtaining a realistic value for $m_b/m_\tau$, which further improves the precision from gauge coupling unification, allowing the QCD coupling constant to be predicted to the level of 1 % or, alternatively, the top quark mass to 0.2 %. Future measurements of these parameters may significantly constrain the detailed structure of the theory. We also study an $SO(10)$ embedding of quark and lepton masses, showing how large neutrino mixing is compatible with small quark mixing, and predict a normal neutrino mass hierarchy. The strong CP problem may be explained by combining Higgs Parity with space-time parity.