81 research outputs found
A strong first order phase transition in the UMSSM
In this work, the electroweak phase transition (EWPT) strength has been
investigated within the extended Minimal Supersymmetric Standard Model
(UMSSM) without introducing any exotic fields. We found that the EWPT could be
strongly first order for reasonable values of the lightest Higgs and neutralino
masses.Comment: talk presented in PASCOS2010, Valencia, Spain from 19-23 Jul. 201
Electroweak Phase Transition in the U(1)' MSSM
In this work, we have investigated the nature of the electroweak phase
transition in the U(1) extended minimal supersymmetric standard model without
introducing any exotic fields. The effective potential has been estimated
exactly at finite temperature taking into account the whole particle spectrum.
For reasonable values of the lightest Higgs and neutralino, we found that the
electroweak phase transition could be strongly first order due to: (1) the
interactions of the singlet with the doublets in the effective potential, and
(2) the evolution of the wrong vacuum that delays the transition.Comment: substantial changes, references added, 18 pages, 4 figure
Sphalerons and the Electroweak Phase Transition in Models with Higher Scalar Representations
In this work we investigate the sphaleron solution in a
gauge theory, which also encompasses the Standard Model, with higher scalar
representation(s) (). We show that the field profiles
describing the sphaleron in higher scalar multiplet, have similar trends like
the doublet case with respect to the radial distance. We compute the sphaleron
energy and find that it scales linearly with the vacuum expectation value of
the scalar field and its slope depends on the representation. We also
investigate the effect of gauge field and find that it is small for the
physical value of the mixing angle, and resembles the case for the
doublet. For higher representations, we show that the criterion for strong
first order phase transition, , is relaxed with respect to
the doublet case, i.e. .Comment: 20 pages, 5 figures & 1 table, published versio
A comprehensive study of neutrino spin-flavour conversion in supernovae and the neutrino mass hierarchy
Resonant spin-flavour (RSF) conversions of supernova neutrinos, which is
induced by the interaction between the nonzero neutrino magnetic moment and
supernova magnetic fields, are studied for both normal and inverted mass
hierarchy. As the case for the pure matter-induced neutrino oscillation
(Mikheyev--Smirnov--Wolfenstein (MSW) effect), we find that the RSF transitions
are strongly dependent on the neutrino mass hierarchy as well as the value of
. Flavour conversions are solved numerically for various neutrino
parameter sets, with presupernova profile calculated by Woosley and Weaver. In
particular, it is very interesting that the RSF-induced
\nu_\rme\to\bar\nu_\rme transition occurs, if the following conditions are
all satisfied: the value of ( is the neutrino magnetic
moment, and is the magnetic field strength) is sufficiently strong, the
neutrino mass hierarchy is inverted, and the value of is large
enough to induce adiabatic MSW resonance. In this case, the strong peak due to
original \nu_\rme emitted from neutronization burst would exist in time
profile of the neutrino events detected at the Super-Kamiokande detector. If
this peak were observed in reality, it would provide fruitful information on
the neutrino properties. On the other hand, characters of the neutrino spectra
are also different between the neutrino models, but we find that there remains
degeneracy among several models. Dependence on presupernova models is also
discussed.Comment: 23 pages, 11 figures, corrected minor typos, added references. Final
version to appear in Journal of Cosmology and Astroparticle Physic
Sphalerons on Orbifolds
In this work, we study the electroweak sphalerons in a 5D background, where
the fifth dimension lies on an interval. We consider two specific cases: flat
space-time and the anti-de Sitter space-time compactified on S^{1}/Z_{2}. In
our work, we take the SU(2) gauge-Higgs model, where the gauge fields reside in
the 5D bulk; but the Higgs doublet is confined in one brane. We find that the
results in this model are close to those of the 4D Standard Model (SM). The
existence of the warp effect, as well as the heaviness of the gauge
Kaluza-Klein modes make the results extremely close to the SM ones.Comment: 10 pages, 4 figures. To appear in EPJ
A model of neutrino mass and dark matter with large neutrinoless double beta decay
We propose a model where neutrino masses are generated at three loop order but neutrinoless double beta decay occurs at one loop. Thus we can have large neutrinoless double beta decay observable in the future experiments even when the neutrino masses are very small. The model receives strong constraints from the neutrino data and lepton flavor violating decays, which substantially reduces the number of free parameters. Our model also opens up the possibility of having several new scalars below the TeV regime, which can be explored at the collider experiments. Additionally, our model also has an unbroken Z2 symmetry which allows us to identify a viable Dark Matter candidate
Supernova Neutrino Spectrum with Matter and Spin Flavor Precession Effects
We consider Majorana neutrino conversions inside supernovae by taking into
account both flavor mixing and the neutrino magnetic moment. We study the
adiabaticity of various possible transitions between the neutrino states for
both normal and inverted hierarchy within the various solar neutrino problem
solutions. From the final mass spectrum within diffrent scenarios, we infer the
consequences of the various conversion effects on the neutronization peak, the
nature of final spectra, and the possible Earth matter effect on the final
fluxes. This enable us to check the sensibility of the SN neutrino flux on
magnetic moment interaction, and narrow down possible scenarios which depend
on: the mass spectrum normal or inverted, the solution of the solar neutrino
problem; and the value of MuxB.Comment: 24pages, 7 figure
Supernova prompt neutronization neutrinos and neutrino magnetic moments
It is shown that the combined action of spin-flavor conversions of supernova
neutrinos due to the interactions of their Majorana-type transition magnetic
moments with the supernova magnetic fields and flavor conversions due to the
mass mixing can lead to the transformation of \nu_e born in the neutronization
process into their antiparticles \bar{\nu}_e. Such an effect would have a clear
experimental signature and its observation would be a smoking gun evidence for
the neutrino transition magnetic moments. It would also signify the leptonic
mixing parameter |U_{e3}| in excess of 10^{-2}.Comment: LaTex, 25 pages, 3 figures. v4: Discussion section expanded,
references added. Matches the published versio
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