Models of Neutrino Masses and Mixing

Neutrino physics has entered an era of precision measurements. With these precise measurements, we may be able to distinguish different models that have been constructed to explain the small neutrino masses and the large mixing among them. In this talk, I review some of the existing theoretical models and their predictions for neutrino oscillations.Comment: Talk presented at the 2nd International Colliders to Cosmic Rays Conference (C2CR07), Lake Tahoe, CA, February 25 - March 1, 2007; 8 pages; 2 figure

Generation of Small Neutrino Majorana Masses in a Randall-Sundrum Model

We propose a model, in the framework of 5D with warped geometry, in which small neutrino Majorana masses are generated by tree level coupling of lepton doublets to a SU(2)_{L}-triplet scalar field, which is coupled to a bulk SM-singlet. The neutrino mass scale is determined by the bulk mass term (alpha_{S}) of the singlet as ve^{-2(alpha_{S}-1)*pi*kR}. This suppression is due to a small overlap between the profile of the singlet zero mode and the triplet, which is confined to the TeV brane. The generic form for the neutrino mass matrix due to the overlap between the fermions is not compatible with the LMA solution. This is overcome by imposing a Z_{4} symmetry, which is softly broken by couplings of the triplet Higgs to the lepton doublets. This model successfully reproduces the observed masses and mixing angles in charged lepton sector as well as in the neutrino sector, in addition to having a prediction of |U_{e3}| ~ O(0.01). The mass of the triplet is of the order of a TeV, and could be produced at upcoming collider experiments. The doubly charged member of the triplet can decay into two same sign charged leptons yielding the whole triplet coupling matrix which, in turn, gives the mixing matrix in the neutrino sector.Comment: 16 pages, 1 figure, RevTeX; v2: version to appear in Phys. Rev.

Model Predictions for Neutrino Oscillation Parameters

We have surveyed leptonic and grand unified models of neutrino masses and mixings in the literature which are still viable and give numerical predictions for the reactor angle, $\theta_{13}$. The results are of considerable interest in anticipation of the next generation reactor experiments and the possible future need for neutrino factories. Of the 63 models considered which were published or posted on the Archive before June 2006, half predict values of \sin^2 2\theta_{13} \gsim 0.015, which should yield positive signals for $\bar{\nu}_e$ disappearance in the reactor experiments planned for the near future. Depending upon the outcome of those experiments, half of the models can be eliminated on the basis of the presence or absence of such an observed $\bar{\nu}_e$ disappearance signal.Comment: 23 pages including 3 figures; published versio

Relating Leptogenesis to Low Energy CP Violation

In the minimal left-right symmetric model with spontaneous CP violation, there are only two intrinsic CP violating phases to account for all CP violation in both the quark and lepton sectors. In addition, the left-and right-handed Majorana mass terms for the neutrinos are proportional to each other due to the parity in the model. This is thus a very constrained framework, making the existence of correlations among the CP violation in leptogenesis, neutrino oscillation and neutrinoless double beta decay possible.Comment: 4 pages; to appear in Proceedings of SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine, California, 12-17 June 200

Lepton Flavor Violating Decays, Soft Leptogenesis and SUSY SO(10)

We investigate lepton flavor violating decays in a SUSY SO(10) model with symmetric textures recently constructed by us. Unlike the models with lop-sided textures which give rise to a large decay rate for mu -> e gamma, the decay rate we get is much suppressed and yet it is large enough to be accessible to the next generation of experiments. We have also investigated the possibility of baryogenesis resulting from soft leptogenesis. We find that with the soft SUSY masses assuming their natural values, B^\prime \equiv \sqrt{BM_{1}} ~ 1.4 TeV and Im(A) ~ 1 TeV, the observed baryon asymmetry in the Universe can be accommodated in our model. We have also updated the predictions of our model for the masses, mixing angles and CP violating measures in both charged fermion and neutrino sectors, using the most up-to-date experimental data as input.Comment: RevTeX, 22 pages, 9 figures; v2: references added, version to appear in Phys. Rev.