Abundances of new stable particles produced in the early universe

Abstract The standard model of the early universe is used to estimate the present abundances of possible absolutely-stable hadrons or charged leptons more massive than the proton. It is found that experimental limits on their present abundances indicate that no such particles exist with masses below about 16 GeV/c2. Forthcoming experiments could increase this limit to masses up to around 300 GeV/c2.