Particle Physics — UPSC IFoS 2014 Physics PYQ

Explain why each of the following reactions is forbidden :

(i) p + p \rightarrow p + p + n

(ii) p + p \rightarrow p + \pi^+ + \gamma

(iii) \Xi^0 \rightarrow n + \pi^0

(iv) \Lambda \rightarrow p + \pi^0

(v) u_e + p \rightarrow n + e^+