Xing, ZZ (reprint author), Chinese Acad Sci, Inst High Energy Phys & Theoret Phys, Ctr Sci Facil, POB 918, Beijing 100049, Peoples R China.
In the type-1 seesaw mechanism, both the light Majorana neutrinos (nu(1), nu(2), nu(3)) and the heavy Majorana neutrinos (N(1),..., N(n)) can mediate the neutrinoless double-beta (0 nu beta beta) decay. We point out that the contribution of nu(i) to this 0 nu beta beta process is also dependent on the masses M(k) and the mixing parameters R(ek) of N(k) as a direct consequence of the exact seesaw relation, and the effective mass term of nu(i) is in most cases dominant over that of N(i). We obtain a new bound vertical bar Sigma R(ek)(2)M(k)vertical bar < 0.23 eV (or < 0.85 eV as a more conservative limit) at the 2 sigma level, which is much stronger than vertical bar Sigma R(ek)(2)M(k)(-1)vertical bar < 5 x 10(-8) GeV(-1) used in some literature, from current experimental constraints on the 0 nu beta beta decay. Taking the minimal type-1 seesaw scenario for example, we illustrate the possibility of determining or constraining two heavy Majorana neutrino masses by using more accurate low-energy data on lepton number violation and non-unitarity of neutrino mixing. (C) 2009 Elsevier B.V. All rights reserved.