54,914 research outputs found
Low scale Seesaw model and Lepton Flavor Violating Rare B Decays
We study lepton flavor number violating rare B decays, , in a seesaw model with low scale singlet Majorana neutrinos
motivated by the resonant leptogenesis scenario. The branching ratios of
inclusive decays with two almost
degenerate singlet neutrinos at TeV scale are investigated in detail. We find
that there exists a class of seesaw model in which the branching fractions of and can be as large as and
within the reach of Super B factories, respectively, without being in
conflict with neutrino mixings and mass squared difference of neutrinos from
neutrino data, invisible decay width of and the present limit of .Comment: 19 pages, 6 figure
Cosmological Family Asymmetry and CP violation
We discuss how the cosmological baryon asymmetry can be achieved by the
lepton family asymmetries of heavy Majorana neutrino decays and they are
related to CP violation in neutrino oscillation, in the minimal seesaw model
with two heavy Majorana neutrinos. We derive the most general formula for CP
violation in neutrino oscillation in terms of the heavy Majorana masses and
Yukawa mass term. It is shown that the formula is very useful to classify
several models in which , and leptogenesis can be separately
realized and to see how they are connected with low energy CP violaton. To make
the models predictive, we take texture with two zeros in the Dirac neutrino
Yukawa matrix. In particular, we find some interesting cases in which CP
violation in neutrino oscillation can happen while lepton family asymmetries do
not exist at all. On the contrary, we can find , and
leptogenesis scenarios in which the cosmological CP violation and low
energy CP violation measurable via neutrino oscillations are very closely
related to each other. By determining the allowed ranges of the parameters in
the models, we predict the sizes of CP violation in neutrino oscillation and
. Finally, the leptonic unitarity triangles are reconstructed.Comment: 22 pages, 9 figures A figure caption correcte
Leptogenesis and Low energy CP violation, a link
How is CP violation of low energy related to CP violation required from
baryon number asymmetry ? We give an example which shows a direct link between
CP violation of neutrino oscillation and baryogenesis through leptogenesis.Comment: 3 pages and 2 figures, Talk presented at 4th Nufac02, July 1-6, 200
Instrumental Variables Estimation with Some Invalid Instruments and its Application to Mendelian Randomization
Instrumental variables have been widely used for estimating the causal effect
between exposure and outcome. Conventional estimation methods require complete
knowledge about all the instruments' validity; a valid instrument must not have
a direct effect on the outcome and not be related to unmeasured confounders.
Often, this is impractical as highlighted by Mendelian randomization studies
where genetic markers are used as instruments and complete knowledge about
instruments' validity is equivalent to complete knowledge about the involved
genes' functions.
In this paper, we propose a method for estimation of causal effects when this
complete knowledge is absent. It is shown that causal effects are identified
and can be estimated as long as less than % of instruments are invalid,
without knowing which of the instruments are invalid. We also introduce
conditions for identification when the 50% threshold is violated. A fast
penalized estimation method, called sisVIVE, is introduced for
estimating the causal effect without knowing which instruments are valid, with
theoretical guarantees on its performance. The proposed method is demonstrated
on simulated data and a real Mendelian randomization study concerning the
effect of body mass index on health-related quality of life index. An R package
\emph{sisVIVE} is available online.Comment: 99 pages, 29 figures, 14 table
Neutrino masses along with fermion mass hierarchy
Recently a new mechanism has been proposed to cure the problem of fermion
mass hierarchy in the Standard Model (SM) model. In this scenario, all SM
charged fermions other than top quark arise from higher dimensional operators
involving the SM Higgs field. This model also predicted some interesting
phenomenology of the Higgs boson. We generalize this model to accommodate
neutrino masses (Dirac & Majorana) and also obtain the mixing pattern in the
leptonic sector. To generate neutrino masses, we add extra three right handed
neutrinos in this model.Comment: 20 pages, the content on results and phenomenology have been
expanded, a new section on UV completion of the model has been added and also
some new references, this version has been accepted by Physical Review
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