arXiv subjects

J. I. Silva-Marcos

Publications and source records attributed to J. I. Silva-Marcos.

43 records · Page 3Linked to original sources

arXiv2000

Large Neutrino Mixing with Universal Strength of Yukawa Couplings

We analyse, within the framework of universal strength for Yukawa couplings (USY), various structures for the Dirac and Majorana neutrino mass matrices giving rise, through the see-saw mechanism, to a degenerate mass spectrum. A specific USY ansatz is presented for the charged lepton and neutrino effective mass matrix, leading to quasi-degenerate neutrinos and a leptonic mixing matrix which provides a large angle solution for both the atmospheric and solar neutrino problems.

hep-ph↗

arXiv1999

An Alternative to See-Saw

We give a new mechanism for generating very small, and almost degenerate, neutrino masses, without resorting to the see-saw mechanism or unnatural small Yukawa couplings. It requires the existence of at least 4 families with an almost democratic structure for the Yukawa couplings. It is also proven that this structure can account for large lepton mixings of the three light leptons.

hep-ph↗

arXiv1998

Special Symmetric Quark Mass Matrices

We give a procedure to construct a special class of symmetric quark mass matrices near the democratic limit of equal Yukawa couplings for each sector. It is shown that within appropriate weak-bases, the requirements of symmetry and arg(det[M])=0 are very strong conditions, that necessarily lead to a Cabibbo angle given by |V_us|=Sqrt[md/ms], and to |V_cb|~ms/mb, in first order. In addition, we prove that the recently classified ansatze, which also reproduce these mixing relations, and which were based on the hypothesis of the Universal Strength for Yukawa couplings, where all Yukawa couplings have equal moduli while the flavour dependence is only in their phases, are, in fact, particular cases of the generalized symmetric quark mass matrix ansatze we construct here. In an excellent numerical example, the experimental values on all quark mixings and masses are accommodated, and the CP violation phase parameter is shown to be crucially dependent on the values of mu and V_us.

hep-ph↗

arXiv1998

Degenerate and Quasi Degenerate Majorana Neutrinos

We study mixing and CP violation of three left-handed Majorana neutrinos in the limit of exactly degenerate masses, identify the weak-basis invariant relevant for CP violation and show that the leptonic mixing matrix is parametrized only by two angles and one phase. After the lifting of the degeneracy, this parametrization accommodates the present data on atmospheric and solar neutrinos, as well as double beta decay. Some of the leptonic mixing ansatze suggested in the literature correspond to special cases of this parametrization.

hep-ph↗

arXiv1998

Quasi degenerate Neutrino Masses with Universal Strength Yukawa Couplings

A simple ansatz is proposed for neutrino and charged lepton mass matrices, within the framework of universal strength for Yukawa couplings. In this framework all Yukawa couplings have equal moduli and the flavour dependence is only in their phases. We take into account the solar neutrino deficit and the atmospheric neutrino anomaly, assuming three neutrino families only. The ansatz leads in a natural way to small mixing involving neutrinos of quasi degenerate masses, as required to explain the solar neutrino deficit in the nonadiabatic MSW solution, while having the large mixing necessary to explain the atmospheric neutrino anomaly.

hep-ph↗

arXiv1996

A New Approach to the Yukawa Puzzle

We do a systematic analysis of the question of calculability of CKM matrix elements in terms of quark mass ratios, within the framework of the hypothesis of universality of strength for Yukawa couplings (USY), where all Yukawa couplings have equal moduli, and the flavor dependence is only in their phases. We use the fact that the limit $m_u=m_d=0$ is specially simple in USY, to construct the various ansätze. It is shown that the experimentally observed CKM matrix can be obtained within USY ansätze corresponding to simple relations among phases of Yukawa couplings. Within USY, one finds a natural explanation why Cabibbo mixing is significantly larger than the other CKM mixings. In the most successful of the USY ansätze, one obtains in leading order: $|V_{us}|=\sqrt{m_d/{m_s}}$ ; $ |V_{cb}|=\sqrt{2}(m_s/m_b)$ $ |V_{ub}|= (1/\sqrt{2})\sqrt{m_dm_s/m_b^2}$ ; $|V_{td}|= 3|V_{ub}|$. We study the behavior of this USY ansatz under the renormalization group.

hep-ph↗

arXiv1995

Predicting Vckm with Universal Strength of Yukawa Couplings

We study the question of calculability of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements within the framework of universal strength for Yukawa couplings (USY). We first classify all solutions leading to $m_u=m_d=0$ within USY and then suggest a highly predictive ansatz where all the moduli of the CKM matrix elements are correctly predicted in terms of quark mass ratios, with no free parameters.

hep-ph↗