4,936 research outputs found
Addendum to: Model-dependent and -independent implications of the first Sudbury Neutrino Observatory results
In the light of recent experimental and theoretical improvements, we review
our previous model-independent comparison [hep-ph/0106247] of the
Super-Kamiokande (SK) and Sudbury Neutrino Observatory (SNO) solar neutrino
event rates, including updated values for the ``equalized'' SK datum and for
the reference Standard Solar Model (SSM) B neutrino flux. We find that the
joint SK+SNO evidence for active neutrino flavor transitions is confirmed at
the level of 3.3 standard deviations, independently of possible transitions to
sterile states. Barring sterile neutrinos, we estimate the 3-sigma range for
the B neutrino flux (normalized to SSM) as f_B=0.96 +0.54-0.55.
Accordingly, the 3-sigma range for the energy-averaged nu_e survival
probability is found to be = 0.31 +0.55-0.16, independently of the
functional form of P_ee. An increase of the reference nu_e + d --> p + p + e
cross section by ~3%, as suggested by recent theoretical calculations, would
slightly shift the central values of f_B and of to ~1.00 and ~0.29,
respectively, and would strengthen the model-independent evidence for nu_e
transitions into active states at the level of ~3.6 sigma.Comment: 6 pages + 2 figures. Addendum to hep-ph/010624
Global analysis of three-flavor neutrino masses and mixings
We present a comprehensive phenomenological analysis of a vast amount of data
from neutrino flavor oscillation and non-oscillation searches, performed within
the standard scenario with three massive and mixed neutrinos, and with
particular attention to subleading effects. The detailed results discussed in
this review represent a state-of-the-art, accurate and up-to-date (as of August
2005) estimate of the three-neutrino mass-mixing parameters.Comment: Final version (including a new Appendix), to be published in
"Progress in Particle and Nuclear Physics". Higher-resolution pdf file and
eps figures can be download from http://www.ba.infn.it/~now2004/PPNP_review
Atmospheric, Solar, and CHOOZ neutrinos: a global three generation analysis
We perform a global three generation analysis of the current solar and
atmospheric evidence in favor of neutrino oscillations. We also include the
negative results coming from CHOOZ to constrain the nu_e mixing. We study the
zones of mass-mixing oscillations parameters compatible with all the data. It
is shown that almost pure nu_mu nu_tau oscillations are required to
explain the atmospheric neutrino anomaly and almost pure nu_1 nu_2
oscillations to account for the solar neutrino deficit.Comment: 4 pages, talk given at 36th Rencontres de Moriond: Electroweak
Interactions and Unified Theories, Les Arcs, France, 10-17 Mar 200
Sterile neutrinos as subdominant warm dark matter
In light of recent findings which seem to disfavor a scenario with (warm)
dark matter entirely constituted of sterile neutrinos produced via the
Dodelson-Widrow (DW) mechanism, we investigate the constraints attainable for
this mechanism by relaxing the usual hypothesis that the relic neutrino
abundance must necessarily account for all of the dark matter. We first study
how to reinterpret the limits attainable from X-ray non-detection and
Lyman-alpha forest measurements in the case that sterile neutrinos constitute
only a fraction fs of the total amount of dark matter. Then, assuming that
sterile neutrinos are generated in the early universe solely through the DW
mechanism, we show how the X-ray and Lyman-alpha results jointly constrain the
mass-mixing parameters governing their production. Furthermore, we show how the
same data allow us to set a robust upper limit fs < 0.7 at the 2 sigma level,
rejecting the case of dominant dark matter (fs = 1) at the ~ 3 sigma level.Comment: Minor changes; added references; version accepted for publication in
Phys. Rev.
Neutrino mass and mixing parameters: A short review
We present a brief review of the current status of neutrino mass and mixing
parameters, based on a comprehensive phenomenological analysis of neutrino
oscillation and non-oscillation searches, within the standard three-neutrino
mixing framework.Comment: 11 pages, including 7 figures. Presented at the 40th Rencontres de
Moriond on Electroweak Interactions and Unified Theories, La Thuile, Aosta
Valley, Italy, 5-12 Mar 200
Status of three-neutrino oscillation parameters, circa 2013
The standard three-neutrino (3nu) oscillation framework is being increasingly
refined by results coming from different sets of experiments, using neutrinos
from solar, atmospheric, accelerator and reactor sources. At present, each of
the known oscillation parameters [the two squared mass gaps (delta m^2, Delta
m^2) and the three mixing angles (theta_12}, theta_13, theta_23)] is dominantly
determined by a single class of experiments. Conversely, the unknown parameters
[the mass hierarchy, the theta_23 octant and the CP-violating phase delta] can
be currently constrained only through a combined analysis of various
(eventually all) classes of experiments. In the light of recent new results
coming from reactor and accelerator experiments, and of their interplay with
solar and atmospheric data, we update the estimated N-sigma ranges of the known
3nu parameters, and revisit the status of the unknown ones. Concerning the
hierarchy, no significant difference emerges between normal and inverted mass
ordering. A slight overall preference is found for theta_23 in the first octant
and for nonzero CP violation with sin delta < 0; however, for both parameters,
such preference exceeds 1 sigma only for normal hierarchy. We also discuss the
correlations and stability of the oscillation parameters within different
combinations of data sets.Comment: Updated and revised version, accepted for publication in PRD. The
analysis includes the latest (March 2014) T2K disappearance data: all the
figures and the numerical results have been updated, and parts of the text
have been revised accordingl
Diseño de un sistema de disipación de energía para un edifico en altura
Se considera en este trabajo un edificio sismorresistente aporticado de hormigón armado, de 21 niveles, diseñado para Guayaquil, Ecuador. El objetivo del estudio es desarrollar un procedimiento de diseño de un sistema de disipación pasiva de energía (barras de pandeo restringido) para mejorar los parámetros de respuesta de la estructura original. Se diseñan los disipadores según el procedimiento que se explicita, y luego se realiza un análisis dinámico de historia en el tiempo para la estructura con / sin disipadores, bajo la excitación de 5 acelerogramas. Los resultados del modelo numérico muestran la eficiencia del sistema de disipación propuesto.Postprint (published version
Combined analysis of KamLAND and Borexino neutrino signals from Th and U decays in the Earth's interior
The KamLAND and Borexino experiments have detected electron antineutrinos
produced in the decay chains of natural thorium and uranium (Th and U
geoneutrinos). We analyze the energy spectra of current geoneutrino data in
combination with solar and long-baseline reactor neutrino data, with
marginalized three-neutrino oscillation parameters. We consider the case with
unconstrained Th and U event rates in KamLAND and Borexino, as well as cases
with fewer degrees of freedom, as obtained by successively assuming for both
experiments a common Th/U ratio, a common scaling of Th+U event rates, and a
chondritic Th/U value. In combination, KamLAND and Borexino can reject the null
hypothesis (no geoneutrino signal) at 5 sigma. Interesting bounds or
indications emerge on the Th+U geoneutrino rates and on the Th/U ratio, in
broad agreement with typical Earth model expectations. Conversely, the results
disfavor the hypothesis of a georeactor in the Earth's core, if its power
exceeds a few TW. The interplay of KamLAND and Borexino geoneutrino data is
highlighted.Comment: 12 pages, including 6 figure
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