About Mass, CP and Extra Dimensions

We discuss the notion of mass, mostly for fermions, and its relation to the breaking of CP invariance, the natural symmetry of gauge interactions. In a first model, we show how compactification on a Vortex in 2 extra dimensions leads to a replication of generations in 3+1, with challenging mass patterns, and testable consequences in flavour-changing neutral currents (family-number conserving), both at low energies and at future colliders. In different model, we show how CP violation can result from compactification from 4+1 to 3+1 dimensions.Comment: conf proceedings CICHEP conference, Cair

Anatomy of Mixing-Induced CP Asymmetries in Left-Right-Symmetric Models with Spontaneous CP Violation

We investigate the pattern of CP violation in K, B_d and B_s mixing in a symmetrical SU(2)_R x SU(2)_L x U(1) model with spontaneous CP violation. We calculate the phases of the left and right quark mixing matrices beyond the small phase approximation and perform a careful analysis of all relevant restrictions on the model's parameters from Delta m_K, Delta m_B, epsilon, epsilon'/epsilon and the CP asymmetry in B->J/psi K_S. We find that, with current experimental data, the mass of the right-handed charged gauge boson, M2, is restricted to be in the range 2.75 to 13 TeV and the mass of the flavour-changing neutral Higgs boson, MH, in 10.2 to 14.6 TeV. This means in particular that the decoupling limit M2, MH -> infinity is already excluded by experiment. We also find that the model favours opposite signs of epsilon and sin 2beta and is excluded if sin 2beta > 0.1.Comment: 33 pages Latex with 11 Postscript-Figures (included

Gauge dilution and leptogenesis

In this paper, we examine how gauge interactions can dilute the lepton asymmetry in lepton induced baryogenesis. Constraints imposed on Majorana masses keep this dilution at an acceptable level.Comment: 5 page

Neutrino masses from nonstandard supersymmetry breaking terms

Naturally small Majorana neutrino masses arise from nonstandard supersymmetry breaking terms. This mechanism works in the minimal supersymmetric framework and does not require extra particles or new mass scales. It could also be responsible for proton decay even in the absence of Grand Unification.Comment: 7 pages, 3 eps figures; important note on baryon number violation added; small editorial changes mad

Can colliders disprove leptogenesis?

While leptogenesis is a very solid but hard to check contender for the generation of the observed excess of baryons over anti-baryons in the Universe, we show that the observation of gauge bosons associated with right-handed currents at present or future colliders would suffice to disprove its most canonical mechanism.Comment: Rencontres de la vall\'ee d'Aost

Boron abundance and solar neutrino spectrum distortion

The presence of neutrinos from Boron decay in the flux observed on Earth is attested by the observation of their energy spectrum. Possible distortions of the spectrum investigated in current detectors are often interpreted in terms of evidence in favour or against various schemes of neutrino oscillations. We stress here that a distortion of the spectrum at high energies could also result from an increase in the ratio of neutrinos originating from ($^3$He+p) and $^8$B reactions. While a $^8$B neutrino depletion would contribute to this effect, an increase in the Hep contribution seems also needed to reproduce the preliminary data.Comment: 8 pages, 2 figures; abstract and introduction rewritten to match the conclusions bette

See-saw neutrino masses and large mixing angles in the vortex background on a sphere

In the vortex background on a sphere, a single 6-dimensional fermion family gives rise to 3 zero-modes in the 4-dimensional point of view, which may explain the replication of families in the Standard Model. Previously, it had been shown that realistic hierarchical mass and mixing patterns can be reproduced for the quarks and the charged leptons. Here, we show that the addition of a single heavy 6-dimensional field that is gauge singlet, unbound to the vortex, and embedded with a bulk Majorana mass enables to generate 4D Majorana masses for the light neutrinos through the see-saw mechanism. The scheme is very predictive. The hierarchical structure of the fermion zero-modes leads automatically to an inverted pseudo-Dirac mass pattern, and always predicts one maximal angle in the neutrino see-saw matrix. It is possible to obtain a second large mixing angle from either the charged lepton or the neutrino sector, and we demonstrate that this model can fit all observed data in neutrino oscillations experiments. Also, U_{e3} is found to be of the order ~0.1.Comment: 23 pages, 1 figur

Stimulated Neutrino Conversion and Bounds on Neutrino Magnetic Moments

Recent experiment proposed to observe induced radiative neutrino transitions are confronted to existing bounds on neutrino magnetic moments from earth-based experiments. These are found to exclude any observation by several orders of magnitude, unless the magnetic moments are assumed to be strongly momentum dependent. This possibility is discussed in some generality, and we find that nontrivial dependence of the neutrino form factor may indeed occur, leading to quite unexpected effects, although this is insufficient by orders of magnitude to justify the experiments.Comment: one reference modified + minor changes, 8 pages, plain Late