6,653 research outputs found
Impact of radiative corrections on sterile neutrino scenarios
In sterile neutrino scenarios, radiative corrections induce mass splittings
proportional to the top Yukawa coupling, in contrast to the three active
neutrino case where the induced splittings are proportional to the tau Yukawa
coupling. In view of this, we have analyzed the stability of the four-neutrino
schemes favored by oscillation experiments, consisting in two pairs of nearly
degenerate neutrinos separated by the LSND gap. Requiring compatibility with
the measurements of the abundances of primordial elements produced in Big Bang
Nucleosynthesis, we find that when the heaviest pair corresponds to the solar
neutrinos (mainly an admixture of nu_e - nu_s) the natural mass splitting is
3-5 orders of magnitude larger than the observed one, discrediting the scenario
from a theoretical point of view. On the contrary, the scheme where the
heaviest pair corresponds to the atmospheric neutrinos (mainly an admixture of
nu_mu - nu_tau) is safe from radiative corrections due to the small sterile
component of these mass eigenstates.Comment: 14 pages, LaTeX, 2 figures. Discussion enlarged, references added and
typos correcte
Capital Flows, Exchange Rate Regime, and Macroeconomic Performance in Mexico
international capital flows, exchange rate regime
The Interest Rate-Exchange Rate Link in the Mexican Float
This paper examines empirically the interest rate-exchange rate link in the context of the Mexican experience with a floating exchange regime. The impulse response function derived from an ECM estimated by GMM reveals a lasting positive effect of a currency depreciation on the peso-dollar interest rate differential. Some of the macroeconomic consequences from this pattern are discussed, together with a possible explanation based on the incorporation of the central bank reaction function into private expectations.interest rate-exchange rate link, floating exchange rate regimes
Neutrino properties from Yukawa structure
We discuss the implications for lepton mixing and CP violation of structure
in the lepton mass matrices, for the case that neutrino masses are generated by
the see-saw mechanism with an hierarchical structure for the Majorana masses.
For a particularly interesting case with enhanced symmetry in which the lepton
Dirac mass matrices are related to those in the quark sector, the CHOOZ angle
is near the present limit and the CP violating phase relevant to thermal
leptogenesis and to decay is near maximal.Comment: 13 pages, 7 figures. References added and typos corrected. Mistake in
the discussion of leptogenesis correcte
PAMELA's cosmic positron from decaying LSP in SO(10) SUSY GUT
We propose two viable scenarios explaining the recent observations on cosmic
positron excess. In both scenarios, the present relic density in the Universe
is assumed to be still supported by thermally produced WIMP or LSP (\chi). One
of the scenarios is based on two dark matter (DM) components (\chi,X) scenario,
and the other is on SO(10) SUSY GUT. In the two DM components scenario,
extremely small amount of non-thermally produced meta-stable DM component
[O(10^{-10}) < n_X /n_\chi] explains the cosmic positron excess. In the SO(10)
model, extremely small R-parity violation for LSP decay to e^\pm is naturally
achieved with a non-zero VEV of the superpartner of one right-handed neutrino
(\tilde{\nu}^c) and a global symmetry.Comment: 6 pages, Talks presented in PASCOS, SUSY, and COSMO/CosPA in 201
Theoretical Constraints on the Vacuum Oscillation Solution to the Solar Neutrino Problem
The vacuum oscillation (VO) solution to the solar anomaly requires an
extremely small neutrino mass splitting, Delta m^2_{sol}\leq 10^{-10} eV^2. We
study under which circumstances this small splitting (whatever its origin) is
or is not spoiled by radiative corrections. The results depend dramatically on
the type of neutrino spectrum. If m_1^2 \sim m_2^2 \geq m_3^2, radiative
corrections always induce too large mass splittings. Moreover, if m_1 and m_2
have equal signs, the solar mixing angle is driven by the renormalization group
evolution to very small values, incompatible with the VO scenario (however, the
results could be consistent with the small-angle MSW scenario). If m_1 and m_2
have opposite signs, the results are analogous, except for some small (though
interesting) windows in which the VO solution may be natural with moderate
fine-tuning. Finally, for a hierarchical spectrum of neutrinos, m_1^2 << m_2^2
<< m_3^2, radiative corrections are not dangerous, and therefore this scenario
is the only plausible one for the VO solution.Comment: 13 pages, LaTeX, 3 ps figures (psfig.sty
Neutrino physics and lepton flavour violation: A theoretical overview
We review the theoretical status of neutrino physics and its implications for physics beyond the Standard Model. We also discuss the prospects to observe flavour violation in the charged lepton sector, with special emphasis on the
connection to neutrino parameters
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