Current Status of the Research Interests

	Introduction
	The Standard Model (SM) of particle physics still provides a good theoretical description of physical processes at energies thus far probed by experiment: direct accelerator experiments or measurements of, or bounds on, rare processes. In the minimal SM the neutrinos are assumed to be massless. Neutrinos are the only fermions in the SM without right-handed partners and they are also the only electrically neutral fermions in the theory. The existence of a (lepton number violating) Majorana mass term is forbidden because of the given electroweak breaking sector and the field content of the theory. However, recent experiments show a relatively small non-zero masses for the neutrinos. So any realistic model must produce this non-zero masses when reduced to an effective low-energy theory. It is clear that physics beyond the SM is there. In particular, new phenomena must appear at some scale associated with the existence of neutrino masses. From a phenomenological point of view, the main problem in neutrino physics is to characterize the mass parameters present in the low-energy effective Lagrangian by using the experimental results and future evidence. From a theoretical point of view new physics should appear associated to the existence of a mechanism that accounts for electroweak symmetry breaking. Although consistent at low energies, the existence of a fundamental scalar in the theory, the Higgs field, leads to instabilities at higher energies, requiring a fine tuning of the high energy parameters. Thus it seems quite possible that the standard $SU(3) \bigotimes SU(2) \bigotimes U(1)$ model for particle interactions is a low-energy limit of some underlying theory whose true structure will only become apparent when higher energy scales are probed. A deep understanding of the algebraic relationship between various theories will be of great help in discussing their validity.
	Neutrino Phenomenology
	One important physical issue of this project is the question of neutrino masses  and oscillation. This question is important in both particle physics and astrophysics. Advances in the comprehensive understanding of the pattern of neutrino masses  and mixing only appear in close contact with the very rich neutrino  phenomenology existing at present. Solar neutrinos: a thorough study of solar neutrino oscillations has been performed Nucl.Phys.B634:393 (2002). By starting from a realistic model of matter distribution in the Sun and in the  Earth, and by taking into account the interaction of neutrinos in matter,  predictions have been evaluated for present and future experiments Phys.Rev.D. Moreover the recent KamLAND results have be analyzed hep-ph 0212212. A numerical code has been developed where present data on neutrino oscillations  can be introduced in order to obtain exclusion plots for future experiments. Future experiments: It has been demonstrated that the Borexino and KamLAND experiments will determine in the best possible way the neutrino mass difference and mixing angle related to the solar neutrino oscillations New J.Phys. 5:2 (2003), JHEP XX:XXX (2002). Model building: In a model-independent Monte Carlo approach, we have examined a very large class of textures, in the context of non-Abelian horizontal symmetries; we  have found that neutrino data selects only those charged lepton matrices with left-right asymmetric texture. The large atmospheric mixing angle needs $m_{23}\cong m_{33}$. This result, if combined with similar recent findings for the quark sector in  the B oscillations, can be interpreted as a hint for $SU(5)$ unification. In the neutrino sector strict neutrino anarchy is disfavored by data, and at  least a factor 2 of suppression in the first row and column of the neutrino  Majorana mass matrix is required Phys.Lett.B549:325 (2002).