Question

Using the conservation of baryon number, charge and lepton number, decide if the following reaction is possible:

(a) p+n→p+μ^+ +μ^-

Answer 1

The prticles have the following numbers:

1. Proton $p$: charge = +1, baryon number = 1, lepton number = 0

2. Neutron n: charge = 0, baryon number = 1, lepton number = 0

3. Muon μ^+: charge = +1, baryon number = 0, lepton number =+1

4. Muon μ^-: charge = -1, baryon number = 0, lepton number =-1

Proton cancels from both parts, and obtain the following equations:

Charge: $0 =+1-1\Rightarrow True$

Baryon number: $1 =0+0\Rightarrow False$

Answer. The reaction is forbiden.