341 research outputs found
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
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
Bound on the Dark Matter Density in the Solar System from Planetary Motions
High precision planet orbital data extracted from direct observation,
spacecraft explorations and laser ranging techniques enable to put a strong
constraint on the maximal dark matter density of a spherical halo centered
around the Sun. The maximal density at Earth's location is of the order
and shows only a mild dependence on the slope of the halo
profile, taken between 0 and -2. This bound is somewhat better than that
obtained from the perihelion precession limits.Comment: 7 pages, 1 figur
Searching for family-number conserving neutral gauge bosons from extra dimensions
Previous studies have shown how the three generations of the Standard Model
fermions can arise from a single generation in more than four dimensions, and
how off-diagonal neutral couplings arise for gauge-boson Kaluza-Klein
recurrences. These couplings conserve family number in the leading
approximation. While an existing example, built on a spherical geometry,
suggests a high compactification scale, we conjecture that the overall
structure is generic, and work out possible signatures at colliders, compatible
with rare decays data.Comment: 4 pages, 2 figures, jetpl.cls style, references adde
MeV Right-handed Neutrinos and Dark Matter
We consider the possibility of having a MeV right-handed neutrino as a dark
matter constituent. The initial reason for this study was the 511 keV spectral
line observed by the satellite experiment INTEGRAL: could it be due to an
interaction between dark matter and baryons? Independently of this, we find a
number of constraints on the assumed right-handed interactions. They arise in
particular from the measurements by solar neutrino experiments. We come to the
conclusion that such particles interactions are possible, and could reproduce
the peculiar angular distribution, but not the rate of the INTEGRAL signal.
However, we stress that solar neutrino experiments are susceptible to provide
further constraints in the future.Comment: 7 pages, figure 1 changed, added reference
3D-conjugated systems based on oligothiophenes and phosphorus nodes
3D-conjugated systems based on oligothiophene segments grafted on a phosphorus or on a phosphine oxide node have been synthesized. Under Stille coupling conditions, bromide terminated thienyl phosphine derivatives undergo a breaking of the phosphorus–carbon bond attributed to a ligand exchange with the Pd catalyst. The electronic properties of the new compounds have been analyzed by UV-vis and fluorescence spectroscopy and cyclic voltammetry
Synthesis, spectroscopic and electrochemical properties of new covalent assemblies between TTF and various acceptors
Five new acceptor-π–TTF-π-acceptor (A–D–A) triads that contain pyridine, quinoline, nitrophenyl or nitrofuryl groups as acceptor unit have been synthesized by two-fold Wittig olefination reactions and their electrochemical behavior has been studied by cyclic voltammetry (CV). The intramolecular charge transfer (ICT) band in these molecules was characterized by UV–visible electronic absorption spectroscopy and these studies were completed by DFT calculations in the gas phase. These materials appear to be good candidates for the preparation of electroactive discrete metal complexes or coordination polymers as well as for the preparation of radical cations salts
Could the MSSM have no CP violation in the CKM matrix?
We show that all CP violation in the MSSM could originate in the
supersymmetry breaking sector rather than the CKM matrix, and discuss the
important consequences for -physics.Comment: 12 pages + 4 figures, requires epsf.sty, small error +
acknowledgement change
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