Question 2

A charged kaon $K^+$ which has mass 494 MeV$/c^2$, is moving with momentum 300 MeV$/c$. Find its total energy and its velocity.

[6 marks]

The kaon decays into a muon of mass 106 MeV$/c^2$ and a massless neutrino

$$K^+\rightarrow \mu^++\nu.$$

Find the energy of the muon in the rest frame of the kaon.

[10 marks]

In the laboratory frame, where the kaon's momentum is 300 MeV$/c$, the neutrino is emitted in the opposite direction to that of the kaon. Find the energy of the neutrino and hence determine the energy of the muon in this frame.

[9 marks]

[Hints can be found here, but do not follow this link until you have attempted the question on your own.]