Seesaw neutrino masses and mixing with extended democracy

In the context of a minimal extension of the Standard Model with three extra heavy right-handed neutrinos, we propose a model for neutrino masses and mixing based on the hipothesis of a complete alignment of the lepton mass matrices in flavour space. Considering a uniform quasi-democratic structure for these matrices, we show that, in the presence of a highly hierarchical right-handed neutrino mass spectrum, the effective neutrino mass matrix, obtained through the seesaw mechanism, can reproduce all the solutions of the solar neutrino problem.Comment: Latex, 3pages. Uses espcrc2.sty. Talk given at the Europhysics Neutrino Oscillation Workshop - NOW 2000. To appear in Nucl. Phys. B, Proceedings Supplement

Radiative leptogenesis in minimal seesaw models

In the framework of seesaw models with only two heavy Majorana neutrinos, nonzero leptonic asymmetries can be radiatively generated when exact heavy neutrino mass degeneracy ($M_1=M_2=M$) is imposed at a scale $\Lambda_D > M$. For a specific case, we show that an acceptable value for the baryon asymmetry of the Universe can be obtained considering thermal leptogenesis.Comment: Talk given at NOW 2004: Neutrino Oscillation Workshop, Conca Specchiulla, Otranto, Italy, 11-17 Sep 200

Water use in the São Francisco River basin, Brazil: an interregional input-output analysis

The planning and management of water resources aiming to a sustainable development must necessary pass through a series of studies that will reveal the interrelations and links among economic activities, and if one is considering that there is a set regions involved in the process, the direct and indirect regional interdependencies. Increasing demands of water-use for industrial, agricultural and urban sectors may became very competitive and can result in conflicts among multiple users. In the case of the São Francisco River Basin, Brazil, consisting of a wide-range five states - most of them having drought problems - the water in the basin plays an essential role and any activity in this area has to consider the effects of the water use in the intersectoral and interregional economic relations. Considering the three main states in the basin - Minas Gerais, Bahia and Pernambuco - an interregional input-output system for the economy and for the water flows was constructed by the authors. The above interregional system is then used to analyze the interregional and intersectoral dependencies among the states and the economic activities on the São Francisco river basin area and their relations with the use of water

Water use in the São Francisco River basin, Brazil: an interregional input-output analysis

The planning and management of water resources aiming to a sustainable development must necessary pass through a series of studies that will reveal the interrelations and links among economic activities, and if one is considering that there is a set regions involved in the process, the direct and indirect regional interdependencies. Increasing demands of water-use for industrial, agricultural and urban sectors may became very competitive and can result in conflicts among multiple users. In the case of the São Francisco River Basin, Brazil, consisting of a wide-range five states - most of them having drought problems - the water in the basin plays an essential role and any activity in this area has to consider the effects of the water use in the intersectoral and interregional economic relations. Considering the three main states in the basin - Minas Gerais, Bahia and Pernambuco - an interregional input-output system for the economy and for the water flows was constructed by the authors. The above interregional system is then used to analyze the interregional and intersectoral dependencies among the states and the economic activities on the São Francisco river basin area and their relations with the use of water

Removing Ambiguities in the Neutrino Mass Matrix

We suggest that the weak-basis independent condition det(M_nu)=0 for the effective neutrino mass matrix can be used in order to remove the ambiguities in the reconstruction of the neutrino mass matrix from input data available from present and future feasible experiments. In this framework, we study the full reconstruction of M_nu with special emphasis on the correlation between the Majorana CP-violating phase and the various mixing angles. The impact of the recent KamLAND results on the effective neutrino mass parameter is also briefly discussed.Comment: 11 pages, 4 figures. Comments and references added; final version to appear in Phys. Lett.

Enlarging the window for radiative leptogenesis

We investigate the scenario of resonant thermal leptogenesis, in which the leptonic asymmetries are generated through renormalization group corrections induced at the leptogenesis scale. In the framework of the standard model extended by three right-handed heavy Majorana neutrinos with masses M1 = M2 << M3 at some high scale, we show that the mass splitting and CP-violating effects induced by renormalization group corrections can lead to values of the CP asymmetries large enough for a successful leptogenesis. In this scenario, the low-energy neutrino oscillation data can also be easily accommodated. The possibility of having an underlying symmetry behind the degeneracy in the right-handed neutrino mass spectrum is also discussed.Comment: 20 pages, 2 figures, final version to appear in Phys. Lett.

Neutrino masses and mixing with seesaw mechanism and universal breaking of extended democracy

In the framework of a minimal extension of the SM, where the only additional fields are three right-handed neutrinos, we suggest that the charged lepton, the Dirac neutrino and the right-handed Majorana neutrino mass matrices are all, to leading approximation, proportional to the democratic matrix. With the further assumption that the breaking of this extended democracy is universal for all leptonic mass matrices, a large mixing in the 2-3 sector can be obtained and is linked to the seesaw mechanism, together with the existence of a strong hierarchy in the masses of right-handed neutrinos. The structure of the resulting effective mass matrix of light neutrinos is stable against the RGE evolution, and a good fit to all solar and atmospheric neutrino data is obtained.Comment: LaTeX, 17 pages, 2 eps figures. A section on RGE evolution and a few references added; minor typos correcte

Neutrinoless Double Beta Decay in Light of SNO Salt Data

In the SNO data from its salt run, probably the most significant result is the consistency with the previous results without assuming the 8B energy spectrum. In addition, they have excluded the maximal mixing at a very high confidence level. This has an important implication on the double beta decay experiments. For the inverted or degenerate mass spectrum, we find |_{ee}| > 0.013 eV at 95% CL, and the next generation experiments can discriminate Majorana and Dirac neutrinos if the inverted or degenerate mass spectrum will be confirmed by the improvements in cosmology, tritium data beta decay, or long-baseline oscillation experiments.Comment: REVTEX4, three figures. Now uses the updated SK atmospheric data rather than naive rescaling. Conclusion unchanged. References adde

Neutrino Masses, Mixing and New Physics Effects

We introduce a parametrization of the effects of radiative corrections from new physics on the charged lepton and neutrino mass matrices, studying how several relevant quantities describing the pattern of neutrino masses and mixing are affected by these corrections. We find that the ratio omega = sin theta / tan theta_atm is remarkably stable, even when relatively large corrections are added to the original mass matrices. It is also found that if the lightest neutrino has a mass around 0.3 eV, the pattern of masses and mixings is considerably more stable under perturbations than for a lighter or heavier spectrum. We explore the consequences of perturbations on some flavor relations given in the literature. In addition, for a quasi-degenerate neutrino spectrum it is shown that: (i) starting from a bi-maximal mixing scenario, the corrections to the mass matrices keep tan theta_atm very close to unity while they can lower tan theta_sol to its measured value; (ii) beginning from a scenario with a vanishing Dirac phase, corrections can induce a Dirac phase large enough to yield CP violation observable in neutrino oscillations.Comment: 14 pages, 21 figures. Uses RevTeX4. Added several comments and references. Final version to appear in PR

Leptogenesis, CP violation and neutrino data: What can we learn?

A detailed analytic and numerical study of baryogenesis through leptogenesis is performed in the framework of the standard model of electroweak interactions extended by the addition of three right-handed neutrinos, leading to the seesaw mechanism. We analyze the connection between GUT-motivated relations for the quark and lepton mass matrices and the possibility of obtaining a viable leptogenesis scenario. In particular, we analyze whether the constraints imposed by SO(10) GUTs can be compatible with all the available solar, atmospheric and reactor neutrino data and, simultaneously, be capable of producing the required baryon asymmetry via the leptogenesis mechanism. It is found that the Just-So^2 and SMA solar solutions lead to a viable leptogenesis even for the simplest SO(10) GUT, while the LMA, LOW and VO solar solutions would require a different hierarchy for the Dirac neutrino masses in order to generate the observed baryon asymmetry. Some implications on CP violation at low energies and on neutrinoless double beta decay are also considered.Comment: 36 pages, 6 figures; new references added, final version to appear in Nucl. Phys.