Possible solutions to a problem regarding these particles are given in the “Normal” and “Inverted” Hierarchies. (15[1])Two W-minus bosons exchange one of these particles in a proposed mechanism sought after by the EXO-200 experiment. (-5[3])In a parametrization of these particles, a free quantity characterizing CP-violation is represented (15[1]-5[1])by (-5[1])the (-5[1])phase (-5[1])factor (15[1]-5[1])“delta,” (15[1])which appears along with three angles in the PMNS (15[3])matrix. (15[13])Two down quarks are converted into up quarks (15[1])with the release of electrons (15[1])in a hypothetical (15[1])form of (*) double (10[1])beta decay that does not produce these particles (10[4]-5[1])in which they are required (-5[1])to be their own antiparticle. (10[5]-5[2])Because they don’t (10[1])interact with any force except (10[1])gravity, right-handed (10[2])versions (10[1])of these particles are called “sterile.” (10[1])For (10[1])10 points, identify these leptons whose name comes from a combination (10[1])of their low mass and zero charge. (10[3])■END■ (10[12]0[3])