15,944 research outputs found
Effect of steriles states on lepton magnetic moments and neutrinoless double beta decay
We address the impact of sterile fermion states on the anomalous magnetic
moment of charged leptons, as well as their contribution to neutrinoless double
beta decays. We illustrate our results in a minimal, effective extension of the
Standard Model by one sterile fermion state, and in a well-motivated framework
of neutrino mass generation, embedding the Inverse Seesaw into the Standard
Model. The simple "3+1" effective case succeeds in alleviating the tension
related to the muon anomalous magnetic moment, albeit only at the 3
level, and for light sterile states (corresponding to a }cosmologically
disfavoured regime). Interestingly, our analysis shows that a future observation does not necessarily imply an inverted hierarchy for the
active neutrinos in this simple extension. Although the Inverse Seesaw
realisation here addressed could indeed ease the tension in , bounds
from lepton universality in kaon decays mostly preclude this from happening.
However, these scenarios can also have a strong impact on the interpretation of
a future signal regarding the hierarchy of the active neutrino
mass spectrum.Comment: 25 pages, 19 figure
Radiative corrections to from three generations of Majorana neutrinos and sneutrinos
In this work we study the radiative corrections to the mass of the lightest
Higgs boson of the MSSM from three generations of Majorana neutrinos and
sneutrinos. The spectrum of the MSSM is augmented by three right handed
neutrinos and their supersymmetric partners. A seesaw mechanism of type I is
used to generate the physical neutrino masses and oscillations that we require
to be in agreement with present neutrino data. We present a full one-loop
computation of these Higgs mass corrections, and analyze in full detail their
numerical size in terms of both the MSSM and the new (s)neutrino parameters. A
critical discussion on the different possible renormalization schemes and their
implications is included.Comment: 42 pages, 39 figures, 1 appendix, version published in AHE
Summary of the NOW'98 Phenomenology Working Group
Summary of the Phenomenology Working Group at the Europhysics Neutrino
Oscillation Workshop (NOW'98), 7-9 September 1998, Amsterdam.Comment: 66 page
The Increase in the Primordial He-4 Yield in the Two-Doublet Four-Neutrino Mixing Scheme
We assess the effects on Big Bang Nucleosynthesis (BBN) of lepton number
generation in the early universe resulting from the two-doublet four-neutrino
mass/mixing scheme. It has been argued that this neutrino mass/mixing
arrangement gives the most viable fit to the existing data. We study full 4 x 4
mixing matrices and show how possible symmetries in these can affect the BBN
He-4 abundance yields. Though there is as yet no consensus on the reliability
of BBN calculations with neutrino flavor mixing, we show that, in the case
where the sign of the lepton number asymmetry is unpredictable, BBN
considerations may pick out specific relationships between mixing angles. In
particular, reconciling the observed light element abundances with a
\bar\nu_\mu \bar\nu_e oscillation interpretation of LSND would allow unique
new constraints on the neutrino mixing angles in this model.Comment: 12 pages, including 4 figures, to appear in Phys. Rev.
Higgs Boson Masses in the MSSM with Heavy Majorana Neutrinos
We present a full diagrammatic computation of the one-loop corrections from
the neutrino/sneutrino sector to the renormalized neutral CP-even Higgs boson
self-energies and the lightest Higgs boson mass, Mh, within the context of the
so-called MSSM-seesaw scenario. This consists of the Minimal Supersymmetric
Standard Model with the addition of massive right handed Majorana neutrinos and
their supersymmetric partners, and where the seesaw mechanism is used for the
lightest neutrino mass generation. We explore the dependence on all the
parameters involved, with particular emphasis in the role played by the heavy
Majorana scale. We restrict ourselves to the case of one generation of
neutrinos/sneutrinos. For the numerical part of the study, we consider a very
wide range of values for all the parameters involved. We find sizeable
corrections to Mh, which are negative in the region where the Majorana scale is
large (10^{13}-10^{15} GeV) and the lightest neutrino mass is within a range
inspired by data (0.1-1 eV). For some regions of the MSSM-seesaw parameter
space, the corrections to Mh are substantially larger than the anticipated
Large Hadron Collider precision.Comment: Latex, 50 pages, 15 figures, 6 tables. Discussion improved. Comments
and some new approximate formulae have been added. Published version on JHE
Implications of CHOOZ results for the decoupling of solar and atmospheric neutrino oscillations
We have considered the results of solar and atmospheric neutrino oscillation
experiments in the scheme of mixing of three neutrinos with a mass hierarchy.
It is shown that the recent results of the CHOOZ experiment imply that
|U_{e3}|^2<<1 (U is the neutrino mixing matrix), that the oscillations of solar
neutrinos are described by the two-generation formalism and that the
oscillations of solar and atmospheric neutrinos decouple. It is also shown that
if not only |U_{e3}|^2<<1 but also |U_{e3}|<<1, then the oscillations of
atmospheric neutrinos do not depend on matter effects and are described by the
two-generation formalism. In this case, with an appropriate identification of
the mixing parameters, the two-generation analyses of solar and atmospheric
neutrino data provide direct information on the mixing parameters of three
neutrinos. We discuss the possibility to get information on |U_{e3}|^2 in
long-baseline neutrino oscillation experiments.Comment: 12 pages, no figure
Consistency of the dynamical high-scale type-I seesaw mechanism
We analyze the consistency of electroweak breaking within the simplest
high-scale Standard Model type-I seesaw mechanism. We derive the full two-loop
RGEs of the relevant parameters, including the quartic Higgs self-coupling of
the Standard Model. For the simplest case of bare "right-handed" neutrino mass
terms we find that, with large Yukawa couplings, the Higgs quartic
self-coupling becomes negative much below the seesaw scale, so that the model
may be inconsistent even as an effective theory. We show, however, that the
"dynamical" type-I high-scale seesaw with spontaneous lepton number violation
has better stability properties.Comment: 29 pages, 10 figures, 1 table, Published versio
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