New gauge boson Z' and lepton flavor violating decays and production of   vector mesons
  Considering the constraints on the lepton flavor violating (LFV) couplings of the new gauge boson $Z'$ to ordinary leptons from the experimental upper limit for the LFV process $\ell\rightarrow 3\ell'$, we calculate the contributions of $Z'$ to the LFV decays $V\rightarrow\ell_{i}\ell_{j}$ with $V\in\{\phi,J/\Psi,\Psi(2S),\Upsilon^{(n)}\}$ and $\tau\to\mu(e)\phi$ in the context of several $Z'$ models. We find that all $Z'$ models considered in this paper can produce significant contributions to these decay processes and make the value of the branching ratio $Br(\tau\to e\phi)$ above its experimental upper limit. The experimental upper limit of $\tau\to e\phi$ can give more severe constraints on these $Z'$ models than those given by the rare decay process $\tau\to3e$. 
Chong-Xing Yue and Jia-Rui Zhou
hep-ph