\frac{\alpha}{6\pi G^2_{F}m^2_{\mu}m^2_{H}}(Y^4_{S2} + Y^4_{4}) \approx 9.7\times10^{-11}\end{aligned}$$ respectively. Here we have used the relation $m_{\mu} = \sqrt{3}Y_{4}V'$ shown in Eq. (\[chargemass\]) and assumed the VEV of Higgs $V' \sim M_{W}$ and couplings $Y_{S2} = Y_{4}$. Similarly the estimate of the branching ratio for the $\tau\rightarrow\mu\gamma$ yields $$\begin{aligned}
B(\tau\rightarrow\mu\gamma) \approx 3.4\times10^{-13},\end{aligned}$$ which is well below the current experimental bound given in Eq. (\[LFVbound\]).

Discussion and conclusions
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We minimally extend the three generations $A_{4}$ lepton flavor symmetry to a four generations $A_{5}$ lepton flavor symmetry. We find that the tribimaximal pattern in three generation neutrino mixings survives, and all the mass bounds on SM leptons can be satisfied. Notably, the electron is predicted to be massless at tree level, hence one must calculate $m_{e}$ via quantum corrections. If the masses of the extra heavy leptons are within the reach of the LHC, we should be able to test the model. For a sequential fourth generation of leptons, the LHC with $\sqrt s = 7$ TeV and an integrated luminosity of 1 fb$^{-1}$ of data can exclude fourth generation charged leptons with masses up to 250 GeV [@CRW]. It may be worth while to repeat this analysis for the $A_5$ model where mixings 