Baryon and Lepton Numbers Conservation
This law requires that the total baryon and lepton numbers are the same before and after an interaction occurs. To determine the total baryon number, every baryon is assigned +1 for matter, –1 for antimatter, and 0 for all other particles. The same applied for the electron-lepton, muon-lepton and tau-lepton numbers. These laws are used to easily identify which decay is forbidden for a given unstable particle and their origin is an open question.