189 research outputs found
Lepton asymmetries and the growth of cosmological seed magnetic fields
Primordial cosmological hypermagnetic fields polarize the early
Universe plasma prior to the electroweak phase transition (EWPT).
As a result of the long range parity violating gauge interaction present in
the Standard Model their magnitude gets amplified, opening a new, perturbative
way, of accounting for the observed intergalactic magnetic fields.Comment: 4 pages, no figures, final published version available online at
http://www.iop.org/EJ/abstract/1029-8479/2008/03/06
Chern-Simons anomaly as polarization effect
The parity violating Chern-Simons term in the epoch before the electroweak
phase transition can be interpreted as a polarization effect associated to
massless right-handed electrons (positrons) in the presence of a large-scale
seed hypermagnetic field. We reconfirm the viability of a unified seed field
scenario relating the cosmological baryon asymmetry and the origin of the
protogalactic large-scale magnetic fields observed in astronomy.Comment: 4 pages, latex, matches published versio
Low-energy solar anti-neutrinos
If neutrino conversions within the Sun result in partial polarization of
initial solar neutrino fluxes, then a new opportunity arises to observe the
anti-\nu_e's in future neutrino experiments in the low energy region (such as
BOREXINO or HELLAZ) and thus to probe the Majorana nature of the neutrinos. The
\nu_e -> anti-\nu_e conversions may take place for low energy solar neutrinos
while being unobservable at the Kamiokande and Super-Kamiokande experiments.Comment: Talk given at TAUP 97, Gran Sasso, Italy, Sep. 1997; LaTeX, 3 pages,
1 postscript figure, uses espcrc2.st
A theory for scotogenic dark matter stabilised by residual gauge symmetry
Dark matter stability can result from a residual matter-parity symmetry, following naturally from the spontaneous breaking of the gauge symmetry. Here we explore this idea in the context of the SU(3)⊗SU(3)⊗U(1)⊗U(1) electroweak extension of the standard model. The key feature of our new scotogenic dark matter theory is the use of a triplet scalar boson with anti-symmetric Yukawa couplings. This naturally implies that one of the light neutrinos is massless and, as a result, there is a lower bound for the 0νββ decay rate
Updated limits on visibly and invisibly decaying Higgs bosons from LEP
Talk presented at the XXIX Rencontres de Moriond, Electroweak Interactions and Unified Theories, March 12-19, 1994, MeribelTalk presented at the XXIX Rencontres de Moriond, Electroweak Interactions and Unified Theories, March 12-19, 1994, MeribelTalk presented at the XXIX Rencontres de Moriond, Electroweak Interactions and Unified Theories, March 12-19, 1994, Meribe
A SUSY A4 model for fermion masses and mixings
We study a supersymmetric extension of the Standard Model based on discrete
A4xZ3xZ4 flavor symmetry. We obtain quark mixing angles as well as a realistic
fermion mass spectrum and we predict tribimaximal leptonic mixing by a
spontaneous breaking of A4. The top quark Yukawa interaction is present at the
renormalizable level in the superpotential while all the other Yukawa
interactions arise only at higher orders. We study the Higgs potential and show
that it can potentially solve the so called vacuum alignment problem. The
leading order predictions are not spoiled by subleading corrections.Comment: version accepted in JHEP, Z3xZ2 changed in Z3xZ4, typos in table
corrected, references adde
Bilinear R-parity violating SUSY: Neutrinoless double beta decay in the light of solar and atmospheric neutrino data
Neutrinoless double beta (\znbb) decay is considered within bilinear
R-parity breaking supersymmetry, including the full one-loop corrections to the
neutrino-neutralino mass matrix. Expected rates for \znbb decay in this model
are discussed in light of recent atmospheric and solar neutrino data. We
conclude that (a) tree-level calculations for \znbb decay within the bilinear
model are not reliable in the range of parameters preferred by current solar
and atmospheric neutrino problems. And (b) if the solar and atmospheric
neutrino problems are to be solved within bilinear R-parity violating SUSY the
expected rates for \znbb decay are very low; the effective Majorana neutrino
mass at most 0.01 eV and typical values being one order of magnitude lower.
Observing \znbb decay in the next round of experiments therefore would rule
out the bilinear R-parity violating supersymmetric model as an explanation for
solar and atmospheric neutrino oscillations, as well as any hierarchical scheme
for neutrino masses, unless new neutrino interactions are present.Comment: 1 reference added, enlarged discussion of loop
A potential test of the CP properties and Majorana nature of neutrinos
The scattering of solar neutrinos on electrons may reveal their CP
properties, which are particularly sensitive to their Majorana nature. The
cross section is sensitive to the neutrino dipole moments through an
interference of electro-magnetic and weak amplitudes. We show how future solar
neutrino experiments with good angular resolution and low energy threshold,
such as Hellaz, can be sensitive to the resulting azimuthal asymmetries in
event number, and could therefore provide valuable information on the CP
properties and the nature of the neutrinos, provided the solar magnetic field
direction is fixed.Comment: 14 pages, 1 figure, eq. (19) corrected. Version to be publishe
Bounds on sterile neutrino mixing for cosmologically interesting mass range
This talk summarizes our recent work which studied the impact of resonant
and ( is a sterile
neutrino) conversions on supernova physics, under the assumption that the mass
of the sterile state is in the few eV -cosmologically significant range.Comment: Latex file, 3 pages including 4 ps figures, Talk given by H. Nunokawa
in TAUP97, Gran Sasso, Italy, 7-11 September, 199
Experimental tests for the Babu-Zee two-loop model of Majorana neutrino masses
The smallness of the observed neutrino masses might have a radiative origin.
Here we revisit a specific two-loop model of neutrino mass, independently
proposed by Babu and Zee. We point out that current constraints from neutrino
data can be used to derive strict lower limits on the branching ratio of
flavour changing charged lepton decays, such as .
Non-observation of Br() at the level of would rule
out singly charged scalar masses smaller than 590 GeV (5.04 TeV) in case of
normal (inverse) neutrino mass hierarchy. Conversely, decay branching ratios of
the non-standard scalars of the model can be fixed by the measured neutrino
angles (and mass scale). Thus, if the scalars of the model are light enough to
be produced at the LHC or ILC, measuring their decay properties would serve as
a direct test of the model as the origin of neutrino masses.Comment: 14 pages, 16 figure
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