Question 18M.3.HL.TZ1.6b

A positive pion decays into a positive muon and a neutrino.

$${\pi }^{+}\to {\mu }^{+}+v_{\mu }$$

The momentum of the muon is measured to be 29.8 MeV c^–1 in a laboratory reference frame in which the pion is at rest. The rest mass of the muon is 105.7 MeV c^–2 and the mass of the neutrino can be assumed to be zero.