541 research outputs found
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
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
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
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 (He+p)
and B reactions. While a 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
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