2021-06-16 14:55:30
*The Concept of Lepton Quantum Number in Physics*
What are Leptons?
In physics, leptons are the elementary particles that have a half-integer spin and do not participate in any strong interaction. Since they are elementary particles, they aren't composed of any smaller particles. There are six leptons in the standard model.
Lepton Number
Each of these leptons is assigned a lepton number L = 1. The lepton number of their antimatter counterparts is -1.
L= 1
• electron
• muon
• tau
• electron neutrino
• muon neutrino
• tau neutrino
L = -1
• positron
• antimuon
• antitau
• anti electron neutrino
• anti muon neutrino
• anti tau neutrino
Lepton Number
Lepton number must be conserved in particle interactions. This means the number of leptons/antileptons before and after a particle interaction must be the same. It was introduced in 1953 to explain why we don't see a particular type of particle interaction. Let's look at an example of lepton number conservation.
An example
v⁻ + p → n + e⁺ which is
anti neutrino (-1) + proton (0) → neutron (0) + proton (-1) and it is a correct equation
___________________v⁻ + m → p + e⁻ which is
anti neutrino (-1) + neutron (0) → proton (0) + electron (-1) and it is an incorrect equation
What Else?
Besides the lepton quantum number, there are three more quantum numbers that are absolutely conserved in particle interactions
• Electric charge
• Baryon number
• Weak isospin
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