We investigate a possibility of coexistence of an electron and an electron neutrino in nucleus, by normalization of electroweak interaction. Provided that the electron of atom takes one's share of both electromagnetic and weak interactions, we obtain 2.07 × 10-5 eV as the electron mass for the weak one, from Compton wavelength. This value is close to estimated neutrino mass, 10-5-10-6 eV, giving a possible answer for an unexplained problem of the standard model in particle physics. Thus, we can see that one electron and one neutrino exist in proton and neutron, respectively. Physical roles of electron and neutrino for cold fusion of helium in solid lattice were investigated in terms of elemental particle physics. The electron and neutrino in nucleus enhances the fusion reaction, based on weak interaction in β decays, as well as a catalytic effect of neutral pions.