The reaction p + → e+ + γ is not possible because
A) baryon number is not conserved.
B) lepton number is not conserved.
C) charge is not conserved.
D) energy is not conserved.
E) This reaction IS possible.

Question

The reaction p +  → e+ + γ is not possible because
A) baryon number is not conserved. 
B) lepton number is not conserved. 
C) charge is not conserved. 
D) energy is not conserved. 
E) This reaction IS possible.

Quizplus · Accepted Answer

The reaction violates the conservation of lepton number, as a proton (which has a lepton number of 0) is converted into a positron (which has a lepton number of +1) and a neutrino (which has a lepton number of -1). Therefore, choice B is the correct answer. Choices A, C, and D are not valid reasons for why the reaction is impossible. Choice E is not correct, as explained above.

The Reaction P + → E+ + γ Is