Final answer:
The decay n → e+ + e− is not allowed because it violates the baryon number conservation law, despite conserving lepton number.
Step-by-step explanation:
The decay n → e+ + e− is not possible considering the appropriate conservation laws. For this decay, baryon number conservation and lepton number conservation are crucial. The neutron (n) has a baryon number of +1, while the electron (e−) and the positron (e+) each have a baryon number of 0. The initial state has a baryon number of +1 but the final state has a baryon number of 0, which violates baryon number conservation.
Furthermore, in terms of lepton number, a neutron has a lepton number of 0. An electron has a lepton number of +1 and a positron has a lepton number of −1 because it is the antiparticle of the electron. While the electron-positron pair have lepton numbers that sum to 0, keeping net lepton number the same and satisfying lepton number conservation, the violation of baryon number conservation rules out this decay.
Therefore, the correct answer is b) No, violates baryon number conservation. This decay cannot occur because it would not conserve the baryon number, even though it would conserve lepton number.