Upper Bound on the Proton Lifetime and the Minimal Non-SUSY Grand Unified Theory

In this talk we show that it is possible to find an upper bound on the total proton lifetime. We conclude that the minimal realistic non-supersymmetric grand unified theory is the modified Georgi-Glashow model with a Higgs sector composed of 5_H, 24_H, and 15_H. We discuss the possibility to test this scenario at the next generation of proton decay experiments and future colliders through the production of light scalar leptoquarks.Comment: 8 pages. Based on the Talks given at NURT'06 (V International Symposium on Nuclear and Related Techniques, Havana, CUBA, 3-7 April 2006), PLANCK'06 (The ninth European meeting "From the Planck scale to the ElectroWeak scale", Paris, FRANCE, 29 May 29 - 2 June,2006) and SUSY'06 (14th International Conference on Supersymmetry and the Unification of Fundamental Interactions. Irvine, California, USA. 12-17 June 2006

New Paradigm for Baryon and Lepton Number Violation

The possible discovery of proton decay, neutron-antineutron oscillation, neutrinoless beta decay in low energy experiments, and exotic signals related to the violation of the baryon and lepton numbers at collider experiments will change our understanding of the conservation of fundamental symmetries in nature. In this review we discuss the rare processes due to the existence of baryon and lepton number violating interactions. The simplest grand unified theories and the neutrino mass generation mechanisms are discussed. The theories where the baryon and lepton numbers are defined as local gauge symmetries spontaneously broken at the low scale are discussed in detail. The simplest supersymmetric gauge theory which predicts the existence of lepton number violating processes at the low scale is investigated. The main goal of this review is to discuss the main implications of baryon and lepton number violation in physics beyond the Standard Model.Comment: 60 pages, to appear in Physics Report

Type III Seesaw and Left-Right Symmetry

The implementation of the Type III seesaw mechanism for neutrino masses in the context of left-right theories where parity is broken spontaneously is investigated. We propose a simple left-right symmetric theory where the neutrinos masses are generated through a double seesaw mechanism which is a combination of Type I and Type III seesaw. In this context we find a possible candidate for the cold dark matter in the Universe and discuss the Baryogenesis via Leptogenesis mechanisms. The spectrum of the theory, the phenomenological constraints and the possibility to test the theory at the Large Hadron Collider are investigated.Comment: 5 pages, references added, to appear in JHE

On the Higgs Mass and Perturbativity

The predictions for the Higgs mass in extensions of the Minimal Supersymmetric Standard Model are discussed. We propose a simple theory where the Higgs mass is modified at tree-level and one can achieve a mass around 125 GeV without assuming heavy stops or large left-right mixing in the stop sector. All the parameters in the theory can be perturbative up to the grand unified scale, and one predicts the existence of new colored fields at the TeV scale. We refer to this model as Adjoint MSSM. We discuss the main phenomenological aspects of this scenario and the possible signatures at the Large Hadron Collider.Comment: title and format changed, new plot, to appear in Physics Letters

Sterile Neutrinos and B-L Symmetry

We revisit the relation between the neutrino masses and the spontaneous breaking of the B-L gauge symmetry. We discuss the main scenarios for Dirac and Majorana neutrinos and point out two simple mechanisms for neutrino masses. In this context the neutrino masses can be generated either at tree level or at quantum level and one predicts the existence of very light sterile neutrinos with masses below the eV scale. The predictions for lepton number violating processes such as mu to e and mu to e gamma are discussed in detail. The impact from the cosmological constraints on the effective number of relativistic degree of freedom is investigated.Comment: v2 new section for the LFV processes, minor corrections, main conclusion unchanged, version to appear in Physics Letters