16,697 research outputs found
Status and potentialities of the JUNO experiment
One of the main open issues of neutrino physics is the determination of the
mass hierarchy, discriminating between the two possible ordering of the mass
eigenvalues, known as Normal and Inverted Hierarchies. The solution of this
puzzle would have a significant impact both on elementary particle physics and
astrophysics. A possible way to investigate the problem is the study, with
medium baseline reactor antineutrinos, of the mass dependent corrections to
inverse decays. This is the idea pursued by JUNO, a multipurpose
underground liquid scintillator experiment that will start data taking in very
few years from now. The main characteristics and the status of the experiment
are discussed here, together with its rich physics program. We focus in
particular on the potentiality for mass hierarchy determination, the main goal
of the experiment, on the oscillation parameters accurate measurements and on
the supernova and solar neutrinos and geoneutrino studies.Comment: Invited talk given, on behalf of the JUNO Collaboration, by Vito
Antonelli at the XVII International Workshop on Neutrino Telescopes (Venice,
13-17 March 2017
The flat X-ray spectrum of the LINER NGC1052
We report on ROSAT and ASCA observations of the LINER NGC1052, which is the
first one where broad optical lines in polarized light have been observed. The
2-10 keV spectrum is very flat, with an observed photon index (Gamma) ~0.1. A
model where a nuclear source is - partly or totally - obscured by a screen of
matter with column density ~10^23 atom/cm/cm is the most convincing explanation
for the observed flatness. This agrees with the hypothesis that the LINERs are
a population of low-luminosity AGN, to which the Seyfert unification scenario
applies. The intrinsic spectral index is still rather flat (1.0-1.4), as
observed in a few type-2 Seyferts so far or predicted if the accretion occurs
in an advection-dominated flow.Comment: 5 pages, Latex, 2 Postscript figures, accepted for publication in
MNRA
Neutrino oscillations and Lorentz Invariance Violation in a Finslerian Geometrical model
Neutrino oscillations are one of the first evidences of physics beyond the
Standard Model (SM). Since Lorentz Invariance is a fundamental symmetry of the
SM, recently also neutrino physics has been explored to verify the eventual
modification of this symmetry and its potential magnitude. In this work we
study the consequences of the introduction of Lorentz Invariance Violation
(LIV) in the high energy neutrinos propagation and evaluate the impact of this
eventual violation on the oscillation predictions. An effective theory
explaining these physical effects is introduced via Modified Dispersion
Relations. This approach, originally introduced by Coleman and Glashow,
corresponds in our model to a modification of the special relativity geometry.
Moreover, the generalization of this perspective leads to the introduction of a
maximum attainable velocity which is specific of the particle. This can be
formalized in Finsler geometry, a more general theory of space-time. In the
present paper the impact of this kind of LIV on neutrino phenomenology is
studied, in particular by analyzing the corrections introduced in neutrino
oscillation probabilities for different values of neutrino energies and
baselines of experimental interest. The possibility of further improving the
present constraints on CPT-even LIV coefficients by means of our analysis is
also discussed.Comment: Accepted for publication with minor revisions, will appear on
European Physics Journal
Solar Neutrinos
The study of solar neutrinos has given since ever a fundamental contribution
both to astroparticle and to elementary particle physics, offering an ideal
test of solar models and offering at the same time relevant indications on the
fundamental interactions among particles. After reviewing the striking results
of the last two decades, which were determinant to solve the long standing
solar neutrino puzzle and refine the Standard Solar Model, we focus our
attention on the more recent results in this field and on the experiments
presently running or planned for the near future. The main focus at the moment
is to improve the knowledge of the mass and mixing pattern and especially to
study in detail the lowest energy part of the spectrum, which represents most
of solar neutrino spectrum but is still a partially unexplored realm. We
discuss this research project and the way in which present and future
experiments could contribute to make the theoretical framemork more complete
and stable, understanding the origin of some "anomalies" that seem to emerge
from the data and contributing to answer some present questions, like the exact
mechanism of the vacuum to matter transition and the solution of the so called
solar metallicity problem.Comment: 51 pages, to be published in Special Issue on Neutrino Physics,
Advances in High Energy Physics Hindawi Publishing Corporation 201
Dose of colistin. a work in progress?
We thank Rashid and colleagues [1] and Honoré and colleagues [2] for their comments regarding our article on risk factors for acute kidney injury in pa- tients receiving colistin or other nephrotoxic antimi- crobials [3].
It is correct that we did not specifically report urine output in the text, but it was obviously included in the RIFLE (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease) criteria reported in Table two [3]
Analysis of X-ray flares in GRBs
We present a detailed study of the spectral and temporal properties of the
X-ray flares emission of several GRBs. We select a sample of GRBs which X-ray
light curve exhibits large amplitude variations with several rebrightenings
superposed on the underlying three-segment broken powerlaw that is often seen
in Swift GRBs. We try to understand the origin of these fluctuations giving
some diagnostic in order to discriminate between refreshed shocks and late
internal shocks. For some bursts our time-resolved spectral analysis supports
the interpretation of a long-lived central engine, with rebrightenings
consistent with energy injection in refreshed shocks as slower shells generated
in the central engine prompt phase catch up with the afterglow shock at later
times.Comment: 9 pages, 3 figures. Invited talk at the Swift-Venice 2006 meeting to
be published by "Il Nuovo Cimento
Extinction properties of the X-ray bright/optically faint afterglow of GRB 020405
We present an optical-to-X-ray spectral analysis of the afterglow of GRB
020405. The optical spectral energy distribution not corrected for the
extragalactic extinction is significantly below the X-ray extrapolation of the
single powerlaw spectral model suggested by multiwavelength studies. We
investigate whether considerable extinction could explain the observed spectral
``mismatch'' by testing several types of extinction curves. For the first time
we test extinction curves computed with time-dependent numerical simulations of
dust grains destruction by the burst radiation. We find that an extinction law
weakly depen dent on wavelength can reconcile the unabsorbed optical and X-ray
data with the expected synchrotron spectrum. A gray extinction law can be
provided by a dust grain size distribution biased toward large grains.Comment: 6 pages, 5 figures, accepted for publication on A&
Food Habits of Dicamptodon Ensatus and Associated Fish Species of Maratta Creek, Washington
Three cold-blooded vertebrates, Dicamptodon ensatus, Cottus tenuis, and Salmo gairdneri were investigated as to food habits for a period of one year. The existence of competition between these animals for food was determined by means of stomach analysis. The results were compared relative to each vertebrate and the bottom fauna procurred from the stream. It was shown that the food habits of D. ensatus and S. gairdneri were diverse enough to warrant partial exclusion on the basis of food. C. tenuis demonstrated selectivity and was shown to be under competitive stress from the other two species
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