Beta particles are actually electrons (-e) or can be  positrons.The mass of one electron or beta particle is  9.1095*10-31 kilograms or  0.000548597 AMU which is about 1/20 … 00 times the mass of a  proton or neutron.eta particles are actually electrons (-e) or can be  positrons.The mass of one electron or beta particle is  9.1095*10-31 kilograms or  0.000548597 AMU which is about 1/20 … 00 times the mass of a  proton or neutron.