Exam-style question
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In the reaction π⁻ + p → n + μ⁻ + ν̄_μ, identify the change in baryon number and lepton number and explain why the reaction is allowed.
Model answer
What a good answer should say
- Baryon number is conserved: the initial baryon number is +1 (from the proton) and the final baryon number is +1 (from the neutron).
- Lepton number is conserved: the initial lepton number is 0, and the final lepton number is +1 (from the muon) plus –1 (from the antineutrino), giving 0.
- Therefore the reaction is allowed by conservation laws.
Explanation
Why this works
The answer shows the student can apply conservation of baryon and lepton number to a specific reaction, recognising the roles of the pion, proton, neutron, muon and antineutrino.
Common mistake
No common mistake is linked to this question yet.