 Solution

ID: past-exam-of-the-physics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2013/paper-1/section-a/6/b/solution

γ τ_{0} = 44.7 ns

. Multiplying by the laboratory speed gives

⟨ ℓ ⟩ = v γ τ_{0} ≃ 10.9 m .

This is the mean of the exponential decay-distance distribution, not a fixed distance travelled by every pion.

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