Explicit lepton texture

An explicit form of charged--lepton mass matrix, predicting $m_\tau = 1776.80$~MeV from the experimental values of $m_e$ and $m_\mu$ (in good agreement with the experimental figure $m_\tau = 1777.05^{+0.29}_{-0.26}$ MeV), is applied to three neutrinos $\nu_e$, $\nu_\mu$, $\nu_\tau$ in order to correlate tentatively their masses and mixing parameters. While for charged leptons the off--diagonal mass--matrix elements turn out to be small {\it versus} its diagonal elements, it is suggested that for neutrinos the situation is inverse. Under such a conjecture, the neutrino masses, lepton \CKM matrix and neutrino oscillation probabilities are calculated in the corresponding lowest (and the next to lowest) perturbative order. Then, the nearly maximal mixing of $\nu_\mu$ and $\nu_\tau$ is predicted in consistency with the observed deficit of atmospheric $\nu_\mu$'s. However, the predicted deficit of solar $\nu_e$'s is much too small to explain the observed effect, what suggests the existence of (at least) one sort, $\nu_s$, of sterile neutrinos, whose mixing with $\nu_e$ would be responsible for the observed deficit. In the last Section, promising perspectives for applying the same form of mass matrix to quarks are outlined. Two independent predictions of $|V_{ub}|/|V_{cb}| = 0.0753 \pm 0.0032$ and unitary angle $\gamma \simeq 70^\circ$ are deduced from the experimental values of $|V_{us}|$ and $|V_{cb}|$ (with the use of quark masses $m_s$, $m_c$ and $m_b$).