Minimally modified Fritzsch texture for quark masses and CKM mixing

Abstract

The Standard Model does not constrain the form of the Yukawa matrices and thus the origin of fermion mass hierarchies and mixing pattern remains puzzling. On the other hand, there are intriguing relations between fermion masses and mixing angles which may point towards specific textures of Yukawa matrices. One of the classic hypothesis is the zero texture proposed by Fritzsch which is, however, excluded by present precision tests since it predicts a too large value of $|V_{cb}|$ as well as a too small value of the ratio $|V_{ub}/V_{cb}|$. In this paper we discuss a minimal modification which still maintains the six zero entries as in the original Fritzsch ansatz. This modification consists in introducing an asymmetry between the 23 and 32 entries in the down-quark Yukawa matrix. We show that this flavour structure can naturally emerge in the context of models with inter-family $SU(3)_H$ symmetry. We present a detailed analysis of this Fritzsch-like texture by testing its predictions and showing that it is perfectly compatible with the present precision data on quark masses and CKM mixing matrix.