Beta Decay and the Neutrino

In beta decay a neutron in the nucleus changes to a proton and releases a beta particle (an electron).

The problem with beta decay was that the electrons had a range of energies so the law of conservation of mass-energy is violated, energy disappears. There must be another particle being made with zero mass but variable speeds, the neutrino.

We can also see from the particle conservation laws that this is a forbidden interaction:

Charge Q: 0+1–1 00 Charge is conserved

Baryon Number B: +1+1+0 11 Baryon number is conserved

Lepton Number L: 00+1 01 Lepton number is NOT conserved