What is the conservation of lepton number in particle physics?

The conservation of lepton number in particle physics states that the total number of leptons in a system is conserved.

Leptons are a type of fundamental particle that includes electrons, muons, and neutrinos. The conservation of lepton number is a fundamental principle in particle physics that states that the total number of leptons in a system must remain constant. This means that in any interaction between particles, the total number of leptons before and after the interaction must be the same.

For example, in beta decay, a neutron decays into a proton, an electron, and an antineutrino. In this process, the total number of leptons before and after the interaction is conserved. The neutron, which is not a lepton, is converted into a proton, which is also not a lepton. However, an electron and an antineutrino are produced, which are both leptons. The total number of leptons before and after the interaction is therefore conserved.

The conservation of lepton number is a consequence of the conservation of electric charge, which is also a fundamental principle in particle physics. Since leptons have a charge of -1 or 0, the total number of leptons in a system is related to the total electric charge. This means that any interaction that violates the conservation of lepton number must also violate the conservation of electric charge.