Right unitarity triangles, stable CP-violating phases and approximate quark-lepton complementarity

Current experimental data indicate Chat two unitarity triangles of the CKM quark mixing matrix V are almost the right triangles with alpha approximate to 90 degrees. We highlight a very suggestive parametrization of V and show that its CP-violating phase phi is nearly equal to alpha (i.e., phi - alpha approximate to 1.1 degrees). Both phi and alpha are stable against the renormalizaton-group evolution from the electroweak scale M-Z to a superhigh energy scale M-X or vice versa, and thus it is impossible to obtain alpha approximate to 90 degrees at M-Z from phi = 90 degrees at M-X. We conjecture that there might also exist a maximal CP-violating phase phi approximate to 90 degrees in the MNS lepton mixing matrix U. The approximate quark-lepton complementarity relations, which hold in the standard parametrizations of V and U. can also hold in our particular parametrizations of V and U simply due to the smallness of vertical bar V-ub vertical bar and vertical bar V-e3 vertical bar. (C) 2009 Elsevier B.V. All rights reserved.