The purpose of this Letter is to answer the above question and to confront those six-zero textures of lepton mass matrices with the latest experimental data. First, we shall present a concise analysis of the lepton mass matrices in Table 1 and reveal their isomeric features, namely, they have the same phenomenological consequences, although their structures are apparently different. Second, we shall examine the predictions of these lepton mass matrices by comparing them with the 2σ and 3σ intervals of two neutrino mass-squared differences and three lepton flavor mixing angles,22To be specific, we make use of the 2σ and 3σ intervals of two neutrino mass-squared differences and three lepton flavor mixing angles given by M. Maltoni et al. in Ref. [5]. which are obtained from a global analysis of the latest solar, atmospheric, reactor (KamLAND and CHOOZ [10]) and accelerator (K2K) neutrino data. We find no parameter space allowed for six isomeric lepton mass matrices at the 2σ level. At the 3σ level, however, their results for neutrino masses and lepton flavor mixing angles can be compatible with current data. Third, we incorporate the seesaw mechanism and the Fukugita–Tanimoto–Yanagida hypothesis [9] in the charged lepton and Dirac neutrino mass matrices with six texture zeros. It turns out that their predictions, including θ23≈45°, are in good agreement with the present experimental data even at the 2σ level.
