Xing, ZZ (reprint author), CCAST, World Lab, POB 8730, Beijing 100080, Peoples R China.
Current experimental data indicate that the Koide relation for the pole masses of charged leptons, which can be parametrized as Q(l)(pole) = 2/3, is valid up to the accuracy of O(10(-5)). We show that the running masses of charged leptons fail in satisfying the Koide relation (i.e., Q(l) (mu) not equal 2/3), but the discrepancy between Q(l)(mu) and Q(l)(pole) is only about 0.2% at mu = M-Z. The Koide-like relations for the running masses of neutrinos (1/3 < Q(v)(M-Z) < 0.6), up-type quarks (Q(U)(M-Z)similar to 0.89) and down-type quarks (Q(D)(MZ)similar to 0.74) are also examined from MZ up to the typical seesaw scale M-R similar to 10(14) GeV, and they are found to be nearly stable against radiative corrections. The approximate stability of Q(U)(mu) and Q(D)(mu) is mainly attributed to the strong mass hierarchy of quarks, while that of Q(l)(mu) and Q(v)(mu) is essentially for the reason that the lepton mass ratios are rather insensitive to radiative corrections. (c) 2006 Elsevier B.V. All rights reserved.