483 research outputs found
Mantle geoneutrinos in KamLAND and Borexino
The KamLAND and Borexino experiments have observed, each at ~4 sigma level,
signals of electron antineutrinos produced in the decay chains of thorium and
uranium in the Earth's crust and mantle (Th and U geoneutrinos). Various pieces
of geochemical and geophysical information allow an estimation of the crustal
geoneutrino flux components with relatively small uncertainties. The mantle
component may then be inferred by subtracting the estimated crustal flux from
the measured total flux. To this purpose, we analyze in detail the experimental
Th and U geoneutrino event rates in KamLAND and Borexino, including neutrino
oscillation effects. We estimate the crustal flux at the two detector sites,
using state-of-the-art information about the Th and U distribution on global
and local scales. We find that crust-subtracted signals show hints of a
residual mantle component, emerging at ~2.4 sigma level by combining the
KamLAND and Borexino data. The inferred mantle flux slightly favors scenarios
with relatively high Th and U abundances, within +-1 sigma uncertainties
comparable to the spread of predictions from recent mantle models.Comment: Slight changes and improvements in the text & figures. Results
unchanged. To appear in Phys. Rev.
Probing particle and nuclear physics models of neutrinoless double beta decay with different nuclei
Half-life estimates for neutrinoless double beta decay depend on particle
physics models for lepton flavor violation, as well as on nuclear physics
models for the structure and transitions of candidate nuclei. Different models
considered in the literature can be contrasted - via prospective data - with a
"standard" scenario characterized by light Majorana neutrino exchange and by
the quasiparticle random phase approximation, for which the theoretical
covariance matrix has been recently estimated. We show that, assuming future
half-life data in four promising nuclei (Ge-76, Se-82, Te-130, and Xe-136), the
standard scenario can be distinguished from a few nonstandard physics models,
while being compatible with alternative state-of-the-art nuclear calculations
(at 95% C.L.). Future signals in different nuclei may thus help to discriminate
at least some decay mechanisms, without being spoiled by current nuclear
uncertainties. Prospects for possible improvements are also discussed.Comment: Minor corrections in the text, references added. Matches published
version in Phys. Rev. D 80, 015024 (2009
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
The effect of plant density with different row spacing on quality of the fatty acid composition and grain yield of sunflower
This research was aimed to assess the influence of density with different row spacing on sunflower crop in two different locations in southern Italy. The experiment was laid out in a randomized block design with four replicates. It involved the comparison of sunflower grown in the field on 25 m2-2), obtained by keeping a constant number of plants within the row (3 plants m-1) and varying the spacing between rows (0.4, 0.6 and 0.8 m). In the crops grown at the density of 7.5 plants m-2 (0.4 m row spacing) achene and oil yields were significantly lower as compared to the other treatments. Therefore, the mean values of the two trials did not show any statistical difference between the two densities of 3.75 and 5 plants m-2 (0.8 and 0.6 m row spacing, respectively). However, the superiority in the quality of the fatty acid composition was observed in the crops grown at lower density. Therefore, the row spacing of 0.8 m seems to be a good compromise between achene production and good acid composition of oil.Key words: Helianthus annuus L, plant distribution, plant density, achene yield, oil fatty acid composition
FRCM-to-masonry bonding behaviour in the case of curved surfaces: Experimental investigation
Fabric-reinforced cementitious matrix (FRCM) are composite materials more and more used for the reinforcement of masonry structures. The combination of high tensile strength fabrics (or meshes) with cementitious matrices, having good thixotropic capabilities and vapour permeability, makes such composites suitable for reinforcing a large number of masonry structures, including the one belonging to the historic heritage. FRCMs are bonded to the outer surfaces of structural masonry elements and, thanks to their adhesive capacity, bear much of the tensile stresses that unreinforced masonry cannot withstand. The effectiveness of such reinforcements, which is highly dependent on their ability to adhere to the masonry substrate, is generally investigated throughout specific experimental investigations (shear tests). Almost all the papers in the literature devoted to bond-slip analysis refer to the case of flat bonding surfaces, although these reinforcements are also widely used on curved structural elements such as arches and vaults. Therefore, this paper reports and examines the results of an extensive experimental program concerning the behavior of FRCM systems applied on curved masonry specimens. The results point out the influence of both curvature and reinforcement position (intrados or extrados) on the response of specimens in terms of bearing capacity, failure mode and post-peak response
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
Exploring the Earth’s mantle with geoneutrinos
The KamLAND and Borexino experiments have observed, each
at ∼ 4σ level, signals of electron antineutrinos produced in the decay chains of thorium and uranium in the Earth’s crust and mantle (Th and U geoneutrinos). Various pieces of geochemical and geophysical information allow an estimation of the crustal geoneutrino flux components with relatively small uncertainties. The mantle component may then be inferred by subtracting the estimated crustal flux from the measured total flux. On the base of this approach we find that crustsubtracted signals show hints of a residual mantle component, emerging at ∼ 2.4σ level by combining the KamLAND and Borexino data. The inferred mantle flux
slightly favors scenarios with relatively high Th and U abundances, within ±1σ uncertainties comparable to the spread of predictions from recent mantle models
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