Rare Muon Decay $\mu^+ \to e^+e^-e^+\nu_e\bar{\nu_\mu}$
  An analytical expression for the spin-averaged amplitude squared of the rare muon decay $\mu^+ \to e^+e^-e^+\nu_e\bar{\nu_\mu}$ is calculated. Monte Carlo phase space simulation using the analytical expression for the amplitude has been used to get various differential distributions of charged leptons. The approximate analytical expression for the total energy spectrum of charged leptons near the end point is presented. The dependence of branching ratio on cuts in total energy of charged leptons is studied taking into account an experimental energy resolution. It is shown that the measured branching ratio is very sensitive to the energy resolution. 
Rashid M. Djilkibaev and Rostislav V. Konoplich