Question

Mass of neutron is Mn = 1.008665 amu and mass of proton m_p = 1.007825 amu. The minimum energy of an antineutrino to produce the reaction $\bar{v}$+ p ® n + e⁺, is approximately-

• A. 2 MeV
• B. 5 MeV
• C. 8 MeV
• D. 10 MeV

Answer 1

Answer: (A)

2 MeV

Answer 2

From conservation of energy

E_n + = m_nc² + m_ec² = K_n + K_e

The required neutrino energy will be minimum. When the neutron and positron are both emitted with zero kinetic energy.

(E_n)_min + 938.2 MeV = 939.5 MeV + 0.5 MeV

(E_n)_min = 1.8 MeV