12,673 research outputs found
CP Violation, Sneutrino Oscillation and Neutrino Masses in R-parity Violating Supersymmetric Standard Model
In supersymmetric theories, sneutrino--anti-sneutrino mixing can occur with
the oscillation time ps corresponding the atmospheric neutrino mass
scale eV. We explore the possibility of observing sneutrino
oscillation phenomena and CP violation when R-parity violation explains the
observed neutrino masses and mixing. It is shown for some parameter region in
the bilinear model of R-parity violation that the tiny sneutrino mass splitting
and time-dependent CP violating asymmetries could be measured in the future
experiments if the tau sneutrino is the lightest supersymmetric particle.Comment: 13pp. title changed, new numerical examples added, main conclusions
not changed. version to appear in PL
Axion Dark Matter with High-Scale Inflation
We show that supersymmetric axion models breaking the PQ symmetry by the
interplay of non-renormalizable supersymmetric terms and soft supersymmetry
breaking terms provide a natural framework not only for generating the axion
scale from soft supersymmetry breaking scale but also for enhancing
it during inflation by factor of order where GeV according to the recent BICEP2 result. In this scheme, the PQ
symmetry can stay broken throughout the whole history of the Universe if the
reheat temperature is below GeV, or when the PQ fields
couple strongly to thermal (Standard Model) particles. It is also shown that
parametric resonance during preheating is not effective enough to induce
non-thermal PQ symmetry restoration. As a consequence, axion models with the
QCD anomaly can be made free from the domain wall problem while the
axion isocurvature perturbation is suppressed sufficiently for the axion scale
during inflation larger than about M_P (\Omega_a h^2/0.12)^{1/2} ( F_a/10^{12}
\mbox{GeV})^{0.6} GeV.Comment: 5 page
Muon g2 in two-Higgs-doublet models
Updating various theoretical and experimental constraints on the four
different types of two-Higgs-doublet models (2HDMs), we find that only the
``lepton-specific" (or ``type X") 2HDM can explain the present muon g2
anomaly in the parameter region of large , a light CP-odd boson, and
heavier CP-even and charged bosons which are almost degenerate. The severe
constraints on the models come mainly from the consideration of vacuum
stability and perturbativity, the electroweak precision data, the -quark
observables like , the precision measurements of the lepton
universality as well as the 125 GeV boson property observed at the LHC.Comment: 11 pages, 7 figures, prepared for a review article in Pramana and the
proceedings of FCCP2015. arXiv admin note: text overlap with arXiv:1505.0049
Testing Neutrino Mass Models
The existence of the neutrino masses and mixing would be an important window
into the nature of physics beyond the Standard Model, which will be searched
for in the forthcoming experiments such as LHC. In this talk, we discuss some
examples of neutrino mass models which are testable through the observation of
lepton flavor violating processes and/or electric dipole moments correlated
with the neutrino mass structure.Comment: 7 pages, Plenary talk at PASCOS 200
R-parity Violation and Neutrino Masses
R-parity violation in the supersymmetric standard model could be the origin
of neutrino masses and mixing accounting for the atmospheric and solar neutrino
oscillations. More interestingly, this hypothesis may be tested in future
colliders by detecting lepton number violating decays of the lightest
supersymmetric particle. Here, we present a comprehensive analysis for the
determination of sneutrino vacuum expectation values from the one-loop
effective scalar potential, and also for the one-loop renormalization of
neutrino masses and mixing. Applying our results to theories with gauge
mediated supersymmetry breaking, we discuss the effects of the one-loop
corrections and how the realistic neutrino mass matrices arise.Comment: 4 pages using ws-p8-50x6-00.cl
Analysis of Leptogenesis in Supersymmetric Triplet Seesaw Model
We analyze leptogenesis in a supersymmetric triplet seesaw scenario that
explains the observed neutrino masses, adopting a phenomenological approach
where the decay branching ratios of the triplets and the amount of
CP--violation in its different decay channels are assumed as free parameters.
We find that the solutions of the relevant Boltzmann equations lead to a rich
phenomenology, in particular much more complex compared to the
non--supersymmetric case, mainly due to the presence of an additional Higgs
doublet. Several unexpected and counter--intuitive behaviors emerge from our
analysis: the amount of CP violation in one of the decay channels can prove to
be be irrelevant to the final lepton asymmetry, leading to successful
leptogenesis even in scenarios with a vanishing CP violation in the leptonic
sector; gauge annihilations can be the dominant effect in the determination of
the evolution of the triplet density up to very high values of its mass,
leading anyway to a sizeable final lepton asymmetry, which is also a growing
function of the wash--out parameter K=Gamma_d/H, defined as usual as the ratio
between the triplet decay amplitude Gamma_d and the Hubble constant H; on the
other hand, cancellations in the Boltzmann equations may lead to a vanishing
lepton asymmetry if in one of the decay channels both the branching ratio and
the amount of CP violation are suppressed, but not vanishing. The present
analysis suggests that in the supersymmetric triplet see-saw model successful
leptogenesis can be attained in a wide range of scenarios, provided that an
asymmetry in the decaying triplets can act as a lepton--number reservoir.Comment: 14 pages, 6 figure
Dirac Leptogenesis in extended nMSSM
We show that a version of the nearly Minimal Supersymmetric Standard Model
(nMSSM), extended only in the singlet sector to include the additional
superfields of right-handed neutrinos and very heavy Dirac particles conserving
, admits a viable scenario for Dirac leptogenesis and naturally small
Dirac neutrino masses. The origin of the ()-conserving high singlet
neutrino scale and the desired supersymmetry breaking terms is associated with
dynamical supersymmetry breaking in the hidden sector.Comment: 7 pages, references added, numbering corrected, to be published in
JHE
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