The anomalous lepton magnetic moment, LFV decays and the fourth generation

TL;DR

This paper explores how a hypothetical fourth-generation neutrino could explain the muon g-2 anomaly and LFV decays, using recent experimental data to constrain the model's parameters and assess its viability.

Contribution

It provides new constraints on the fourth-generation neutrino mass and mixing parameters based on LFV decay limits and the muon g-2 anomaly.

Findings

LFV decays and muon g-2 data restrict the fourth neutrino mass range.

Most of the parameter space for the fourth neutrino is excluded by current bounds.

The results impose stringent limits on the existence of a fourth generation neutrino.

Abstract

We investigate the lepton flavor violation (LFV) decays, $\tau\to l\gamma$ ($l=\mu, e$) and $\mu\to e\gamma$, and the newly observed muon $g-2$ anomaly in the framwork of a squential fourth generation model with a heavy fourth neutrino, $\nu'$. By using the recent experimental bounds, we take the constraints of the $4\times 4$ leptonic mixing matrix element factors, $|V_{1\nu'} V_{2\nu'}|^2$, $|V_{1\nu'} V_{3\nu'}|^2 $ and $|V_{3\nu'} V_{2\nu'}|^2$. We find that LFV decays and $g_\mu -2$ can exclude most of the parameter space of the 4th generation neutrino mass $m_{\nu'}$ and give stringent constraints on the existence of the fourth generation.