Question

Given the mean life time of μ⁺ meson is 2.197μs and its branching fraction for μ⁺ → e⁺ + ν_e + bar ν_μ is 100%, estimate the mean lifetime of τ + if the branching fraction B for the decay τ⁺ → e⁺ +ν_e + bar ν_τ is 17.7%. The masses of muon and τ -lepton are 105.658 and 1,784 MeV.

Answer 1

which is in excellent agreement with the experimental value of 0.3 × 10⁻¹² s