Nuclear & Particle Physics - Muon Decay

Which of the following is the principal decay mode of the positive muon μ⁺?

A. μ⁺ → e⁺ + ν_e
B. μ⁺ → p + ν_μ
C. μ⁺ → n + e⁺ + ν_e
D. μ⁺ → e⁺ + ν_e + v̄_μ
E. μ⁺ → π⁺ + v̄_e + ν_μ

(GR0877 #98)

Solution: 

(A) FALSE
μ⁺ → e⁺ + ν_e  violates lepton number: 1 → 1 + 1

(B), (C) FALSE
Muon is elementary particle (lepton), p and n are composite particle (bosons). Elementary particle cannot decay into composite particle, (B), (C) FALSE

(D) TRUE

(E) FALSE
π is pion, which a boson, not a lepton.

Answer: D