2,696 research outputs found
Inductive Logic Programming in Databases: from Datalog to DL+log
In this paper we address an issue that has been brought to the attention of
the database community with the advent of the Semantic Web, i.e. the issue of
how ontologies (and semantics conveyed by them) can help solving typical
database problems, through a better understanding of KR aspects related to
databases. In particular, we investigate this issue from the ILP perspective by
considering two database problems, (i) the definition of views and (ii) the
definition of constraints, for a database whose schema is represented also by
means of an ontology. Both can be reformulated as ILP problems and can benefit
from the expressive and deductive power of the KR framework DL+log. We
illustrate the application scenarios by means of examples. Keywords: Inductive
Logic Programming, Relational Databases, Ontologies, Description Logics, Hybrid
Knowledge Representation and Reasoning Systems. Note: To appear in Theory and
Practice of Logic Programming (TPLP).Comment: 30 pages, 3 figures, 2 tables
Neutrino mass hierarchy and precision physics with medium-baseline reactors: Impact of energy-scale and flux-shape uncertainties
Nuclear reactors provide intense sources of electron antineutrinos,
characterized by few-MeV energy E and unoscillated spectral shape Phi(E).
High-statistics observations of reactor neutrino oscillations over
medium-baseline distances L ~ O(50) km would provide unprecedented
opportunities to probe both the long-wavelength mass-mixing parameters (delta
m^2 and theta_12) and the short-wavelength ones (Delta m^2 and theta_13),
together with the subtle interference effects associated with the neutrino mass
hierarchy (either normal or inverted). In a given experimental setting - here
taken as in the JUNO project for definiteness - the achievable hierarchy
sensitivity and parameter accuracy depend not only on the accumulated
statistics but also on systematic uncertainties, which include (but are not
limited to) the mass-mixing priors and the normalizations of signals and
backgrounds. We examine, in addition, the effect of introducing smooth
deformations of the detector energy scale, E -> E'(E), and of the reactor flux
shape, Phi(E) -> Phi'(E), within reasonable error bands inspired by
state-of-the-art estimates. It turns out that energy-scale and flux-shape
systematics can noticeably affect the performance of a JUNO-like experiment,
both on the hierarchy discrimination and on precision oscillation physics. It
is shown that a significant reduction of the assumed energy-scale and
flux-shape uncertainties (by, say, a factor of 2) would be highly beneficial to
the physics program of medium-baseline reactor projects. Our results also shed
some light on the role of the inverse-beta decay threshold, of geoneutrino
backgrounds, and of matter effects in the analysis of future reactor
oscillation data.Comment: 13 pages, including 17 figures. Minor changes in the text, references
added. To appear in Phys. Rev.
Unbinned test of time-dependent signals in real-time neutrino oscillation experiments
Real-time neutrino oscillation experiments such as Super-Kamiokande (SK), the
Sudbury Neutrino Observatory (SNO), the Kamioka Liquid scintillator
Anti-Neutrino Detector (KamLAND), and Borexino, can detect time variations of
the neutrino signal, provided that the statistics is sufficiently high. We
quantify this statement by means of a simple unbinned test, whose sensitivity
depends on the variance of the signal in the time domain, as well as on the
total number of signal and background events. The test allows a unified
discussion of the statistical uncertainties affecting current or future
measurements of eccentricity-induced variations and of day-night asymmetries
(in SK, SNO, and Borexino), as well as of reactor power variations (in
KamLAND).Comment: 17 pages, including 3 figure
Four-neutrino oscillation solutions of the atmospheric neutrino anomaly
In the context of neutrino scenarios characterized by four (three active plus
one sterile) neutrino species and by mass spectra with two separated doublets,
we analyze solutions to the atmospheric neutrino anomaly which smoothly
interpolate between \nu_\mu-->\nu_\tau and \nu_\mu-->\nu_s oscillations. We
show that, although the Super-Kamiokande data disfavor the pure \nu_\mu-->\nu_s
channel, they do not exclude its occurrence, with sizable amplitude, in
addition to the \nu_\mu-->\nu_\tau channel. High energy muon data appear to be
crucial in assessing the relative amplitude of active and sterile neutrino
oscillations. It is also qualitatively shown that such atmospheric \nu
solutions are compatible with analogous solutions to the solar neutrino
problem, which involve oscillations of \nu_e in both sterile and active states.Comment: Added references. Accepted for publication in Phys. Rev.
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