Precise tests of a quark mass texture

The relations \V-ub/V-cb\ = (mu/mc)(1/2) and \V-td/Vts\ = (m(d)/m(s))(1/2) between the CKM matrix elements and the quark masses are shown to imply a remarkably precise determination of the CKM unitarity triangle or of the Wolfenstein parameters rho, eta consistent with the data so far, We view this as a clean test of a quark mass texture neatly arising from a hierarchical breaking of a U(2) flavour symmetry. (C) 1999 Elsevier Science B.V. All rights reserved.