As well as fundamental Laws of Physics such as The Law of Conservation of Energy and The Law of Conservation of Momentum, they are very specific Laws which musch be obeyed during any nuclear process, and some laws which apply only to certain nuclear processes.
Conservation of Baryon Number: The Hadrons are divided into two groups: the baryons and mesons. The baryons are made up of three quarks, and the mesons are made up of two quarks. If we associate a baryon number of +1with each baryon and a baryon number of -1 with each anti – baryon, we can state the Law as follows:
In any nuclear reaction or decay process, the sum of all the baryon numbers for the reactants equals the sum of all the baryon numbers for the products.
There is also a quality called “strangeness”, which is, as you might expect, strange. Strange particles are always produced in pairs: if a
meson hits a proton, a
and
are produced:
Without the strangeness quality, a neutron should be able to replace the
in the above reaction, but such a reaction never occurs.
Conservation of Strangeness Law: During any nuclear reaction or decay process involving the strong nuclear force, the strangeness of the reactants must equal the strangeness of the products.
Conservation of Lepton Number: It is observed that a neutron may decay into a proton plus an electron, but observation implies energy and momentum are carried away by some third particle. This particle is called the neutrino -labelled
and the equation for neutron decay is:
The bar indicates it is an anti - neutrino and the subscript indicates it is associated with the electron. We may assign a lepton number of +1 to the electron and -1 to the anti – neutrino, and then the sum of the lepton number is aero on both sides. Observations of other decays leads to separate laws for each of the three families of leptons – one each for the electron, muon and tau families.