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

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, ${\nu }^{\prime }$. By using the recent experimental bounds, we take the constraints of the $4\times 4$ leptonic mixing matrix element factors, $|V_{1{\nu }^{\prime }}{V}_{2{\nu }^{\prime }}{|}^2$, $|V_{1{\nu }^{\prime }}{V}_{3{\nu }^{\prime }}{|}^2$ and $|V_{3{\nu }^{\prime }}{V}_{2{\nu }^{\prime }}{|}^2$. We find that LFV decays and $g_{\mu }-2$ can exclude most of the parameter space of the 4th generation neutrino mass $m_{{\nu }^{\prime }}$ and give stringent constraints on the existence of the fourth generation.

Comments: 7 pages, 4 figures, Submitted to Mod. Phys. Lett