Unique mass texture for quarks and leptons - art. no. 051301.

Texture specific quark mass matrices which are Hermitian and hierarchical a re examined in detail. In the case of texture 6 zero matrices, out of sixte en possibilities examined by us, none is able to fit the low energy data (L ED), for example, \V-us\ = 0.2196+/-0.0023, \V-cb\ = 0.0395+/-0.0017, \V-ub /V-cb\ = 0.08+/-0.02, and \V-td\ lies in the range 0.004-0.014 (PDG). Simil arly none of the 32 texture 5 zero mass matrices considered is able to repr oduce the LED. In particular, the latest data from CERN LEP regarding \V-ub /V-cb\ = (0.093+/-0.016) rules out all of them. In the texture 4 zero case, we find that there is a unique texture structure for U and D mass matrices which is able to fit the data. [S0556-2821(99)50415-3].