Conservation of Baryon Number

One of the most important conservation laws of physics is the conservation of baryon number.  All particles have a baryon number based upon the net number of quarks they have. For mesons, which are made up of a quark and an antiquark, they have a baryon number B=0. All baryons, on the other hand, have three quarks, so B=1. Essentially, all quarks are B=1/3. Conservation of baryon number states that this key number must be conserved throughout the decay of all particles. This means that only direct decays are possible, regardless of their energy. The law, in ordinance with conservation of energy, limits what particles can decay into.