Lepton flavor violation decays with the fourth generation neutrino
  We investigate the lepton flavor violation decays, $\tau \to \mu\gamma$, $\tau \to e\gamma$ and $\mu \to e\gamma$, in the framwork of a squential fourth generation model with a heavy fourth neutrino, $\nu'$. Using the recent experimental bounds, we can obtain the constraints of the $4\times 4$ leptonic mixing matrix element factors, $V_{1\nu'},V_{2\nu'}$ and $V_{3\nu'}$. We find that LFV decays can give strigent costraints on the parameter space of the 4th neutrino mass $m_{\nu'}$. 
Wu-Jun Huo and Tai-Fu Feng (IHEP, Cas, China)