Question

Which of the following processes are allowed in electro-magnetic interactions, and which are allowed in weak interactions via the exchange of a single W± or Z0?

(a) K + → π0 + e+ + νe

(b) Σ0 → Λ + νe + νe

Answer 1

(a) It is forbidden as electromagnetic interaction because ΔS ≠ 0 and also forbidden as weak interaction because there is no strangeness changing current

(b) It is allowed as an electromagnetic process because ΔS = 0 (both Σ0 and Λ have = −1. does not apply to e+, and e−)