11.5 Exercise 12

The primary decay mode for the negative pion is $\pi^{−} \rightarrow \mu^{−} + \left(\overset{−}{\nu}\right)_{\mu} .$ (a) What is the energy release in MeV in this decay? (b) Using conservation of momentum, how much energy does each of the decay products receive, given the $\pi^{−}$ is at rest when it decays? You may assume the muon antineutrino is massless and has momentum $p = E / c$, just like a photon.