Seesaw and leptogenesis: a triangular ansatz

A triangular ansatz for the seesaw mechanism and baryogenesis via leptogenesis is explored. In a basis where both the charged lepton and the Majorana mass matrix are diagonal, the Dirac mass matrix can generally be written as the product of a unitary times a triangular matrix. We assume the unitary matrix to be the identity and then an upper triangular Dirac matrix. Constraints from bilarge lepton mixing and leptogenesis are studied.Comment: 6 pages, revised and correcte

Lepton mixing and seesaw mechanism

In the context of a typical model for fermion mass matrices, possibly based on the horizontal U(2) symmetry, we explore the effect of the type II seesaw mechanism on lepton mixings. We find that the combined contribution of type I and type II terms is able to explain the large but not maximal 1-2 mixing and the near maximal 2-3 mixing, while the 1-3 mixing angle is predicted to be small.Comment: 7 pages RevTex4. Revise: comment and reference adde

Baryon asymmetry and mass matrices

In the framework of the baryogenesis via leptogenesis mechanism we study the link between the amount of baryon asymmetry and neutrino mass matrices. In particular, neglecting phases, we find that if the Dirac neutrino mass matrix is related to the up quark mass matrix, the baryon asymmetry is about three orders smaller than the required value. If the Dirac neutrino mass matrix is related to the down quark or the charged lepton mass matrix, the baryon asymmetry is about two orders smaller than the required value. In order to get a sufficient amount of baryon asymmetry we need a more moderate hierarchy in the Dirac neutrino mass matrix.Comment: 11 pages, RevTex. Comment adde

Fermion Mass Matrices in term of the Cabibbo-Kobayashi-Maskawa Matrix and Mass Eigenvalues

A parameter free, model independent analysis of quark mass matrices is carried out. We find a representation in terms of a diagonal mass matrix for the down (up) quarks and a suitable matrix for the up (down) quarks, such that the mass parameters only depend on the six quark masses and the three angles and phase appearing in the Cabibbo-Kobayashi-Maskawa matrix. The results found may also be applied to the Dirac mass matrices of the leptons.Comment: 7 pages LaTeX, no figures. Title changed, Particle Data Group parametrization of CKM matrix used in equation (8), numerical values in table 1 evaluated using the quark mass values at the Z^o mass scale, equation (21) eliminated and 2 references change