Fourth Generation Parity

TL;DR

This paper introduces a simple 4th-generation model with a new gauge symmetry that stabilizes the lightest 4G particle, leading to distinct decay modes and potentially lighter 4G particles than previously constrained.

Contribution

The paper proposes a novel 4G model with a Z_2 residual symmetry (4G-parity) that alters decay modes and allows lighter 4G particles compared to traditional models.

Findings

4G particles can be lighter than experimental bounds due to 4G-parity.

The model predicts a stable 4G neutrino as the lightest particle.

Distinct decay signatures with missing energy are expected.

Abstract

We present a very simple 4th-generation (4G) model with an Abelian gauge interaction under which only the 4G fermions have nonzero charge. The U(1) gauge symmetry can have a Z_2 residual discrete symmetry (4G-parity), which can stabilize the lightest 4G particle (L4P). When the 4G neutrino is the L4P, it would be a neutral and stable particle and the other 4G fermions would decay into the L4P leaving the trace of missing energy plus the standard model fermions. Because of the new symmetry, the 4G particle creation and decay modes are different from those of the sequential 4G model, and the 4G particles can be appreciably lighter than typical experimental bounds.