A free proton does not undergo beta^+ decay because:

  1. protons have no up quarks
  2. it has no charge
  3. a neutron is heavier than a proton, so energy would not be conserved
  4. the weak force doesn't act on protons
Answer

C) a neutron is heavier than a proton, so energy would not be conserved

Happens only inside nuclei with extra binding energy. SLO P-11-F-15 · Knowledge

Physics MCQ · More Nuclear and Particle Physics MCQs · Practise