60 research outputs found
Status of 3-neutrino and 4-neutrino scenarios
Some aspects of the current neutrino oscillation phenomenology are briefly
discussed, with emphasis on the status of mass-mixing parameters relevant for
scenarios with three active neutrinos, and with an additional fourth sterile
neutrino.Comment: 3 pages (including 1 figure). Talk presented at NOW 2000, 2nd
International Europhysics Neutrino Oscillation Workshop (Conca Specchiulla,
Otranto, Italy), September 9-16, 2000, to be published in Nucl. Phys. B
(Proc. Suppl.
Probing the neutrino mass ordering with KM3NeT-ORCA: Analysis and perspectives
The discrimination of the two possible options for the neutrino mass ordering
(normal or inverted) is a major goal for current and future neutrino
oscillation experiments. Such goal might be reached by observing
high-statistics energy-angle spectra of events induced by atmospheric neutrinos
and antineutrinos propagating in the Earth matter. Large volume water-Cherenkov
detectors envisaged to this purpose include the so-called KM3NeT-ORCA project
(in seawater) and the IceCube-PINGU project (in ice). Building upon a previous
work focused on PINGU, we study in detail the effects of various systematic
uncertainties on the ORCA sensitivity to the mass ordering, for the reference
configuration with 9 m vertical spacing. We point out the need to control
spectral shape uncertainties at the percent level, the effects of better priors
on the theta-23 mixing parameter, and the benefits of an improved flavor
identification in reconstructed ORCA events.Comment: 15 pages, including 7 figures. A few paragraphs and references added.
Invited contribution to appear in the JPG Focus Issue on "Neutrino Mass and
Mass Ordering
Majorana neutrino mass constraints in the landscape of nuclear matrix elements
We discuss up-to-date constraints on the Majorana neutrino mass
from neutrinoless double beta decay ()
searches in experiments using different isotopes: KamLAND-Zen and EXO
(Xe), GERDA and MAJORANA (Ge) and CUORE (Te). Best fits
and upper bounds on are explored in the general landscape of
nuclear matrix elements (NME), as well as for specific NME values obtained in
representative nuclear models. By approximating the likelihood of
signals through quadratic forms, the analysis of separate and
combined isotope data becomes exceedingly simple, and allows to clarify various
aspects of multi-isotope data combinations. In particular, we analyze the
relative impact of different data in setting upper bounds on ,
as well as the conditions leading to nonzero at best fit, for
variable values of the NMEs. Detailed results on from various
combinations of data are reported in graphical and numerical form. Implications
for future data analyses and NME calculations are briefly
discussed.Comment: 13 pages, including 6 tables and 7 figure
Neutrinos self interactions in Supernovae
Oscillations of neutrino emerging from a supernova core are studied. In this
extremely high density region neutrino self interactions induce collective
flavor transitions. When collective transitions are decoupled from matter
oscillations, as for our chosen matter profile, an analytical interpretation of
the collective effects is possible, by means of a mechanical analogy with a
spherical pendulum. For inverted neutrino hierarchy the neutrino propagation
can be divided in three regimes: synchronization, bipolar oscillations, and
spectral split. Our simulation shows that averaging over neutrino trajectories
does not alter the nature of these three regimes.Comment: 6 pages, 7 figures, to appear in the Proceedings of the 43rd
Rencontres de Moriond EW session, La Thuile, Italy, 1-8 March 200
Quo vadis neutrino?
Proverò a identificare alcune possibili traiettorie della futura fisica dei neutrini, con un occhio attento soprattutto al lettore non esperto in fisica, ma semplicemente incuriosito da questo campo di ricerca. Per semplicità farò riferimento, oltre ai precedenti articoli di Ithaca sull'argomento, ad alcune voci di Wikipedia (con i loro pregi e difetti)
Quo vadis neutrino?
Proverò a identificare alcune possibili traiettorie della futura fisica dei neutrini, con un occhio attento soprattutto al lettore non esperto in fisica, ma semplicemente incuriosito da questo campo di ricerca. Per semplicità farò riferimento, oltre ai precedenti articoli di Ithaca sull'argomento, ad alcune voci di Wikipedia (con i loro pregi e difetti)
Fast flavor conversions of supernova neutrinos: Classifying instabilities via dispersion relations
Supernova neutrinos can exhibit a rich variety of flavor conversion
mechanisms. In particular, they can experience "fast" self-induced flavor
conversions almost immediately above the core. Very recently, a novel method
has been proposed to investigate these phenomena, in terms of the dispersion
relation for the complex frequency and wave number (,) of
disturbances in the mean field of the flavor coherence. We discuss
a systematic approach to such instabilities, originally developed in the
context of plasma physics, and based of the time-asymptotic behavior of the
Green's function of the system. Instabilities are typically seen to emerge for
complex , and can be further characterized as convective (moving away
faster than they spread) and absolute (growing locally), depending on
-dependent features. Stable cases emerge when (but not ) is
complex, leading to disturbances damped in space, or when both and
are real, corresponding to complete stability. The analytical classification of
both unstable and stable modes leads not only to qualitative insights about
their features but also to quantitative predictions about the growth rates of
instabilities. Representative numerical solutions are discussed in a simple
two-beam model of interacting neutrinos. As an application, we argue that
supernova and binary neutron star mergers exhibiting a "crossing" in the
electron lepton number would lead to an absolute instability in the flavor
content of the neutrino gas.Comment: (v2, revised version: 25 pages, 15 pdf figures. Minor changes.
Figures improved. Matches the version published on PRD
Turbulence patterns and neutrino flavor transitions in high-resolution supernova models
During the shock-wave propagation in a core-collapse supernova (SN), matter
turbulence may affect neutrino flavor conversion probabilities. Such effects
have been usually studied by adding parametrized small-scale random
fluctuations (with arbitrary amplitude) on top of coarse, spherically symmetric
matter density profiles. Recently, however, two-dimensional (2D) SN models have
reached a space resolution high enough to directly trace anisotropic density
profiles, down to scales smaller than the typical neutrino oscillation length.
In this context, we analyze the statistical properties of a large set of SN
matter density profiles obtained in a high-resolution 2D simulation, focusing
on a post-bounce time (2 s) suited to study shock-wave effects on neutrino
propagation on scales as small as O(100) km and possibly below. We clearly find
the imprint of a broken (Kolmogorov-Kraichnan) power-law structure, as
generically expected in 2D turbulence spectra. We then compute the flavor
evolution of SN neutrinos along representative realizations of the turbulent
matter density profiles, and observe no or modest damping of the neutrino
crossing probabilities on their way through the shock wave. In order to check
the effect of possibly unresolved fluctuations at scales below O(100) km, we
also apply a randomization procedure anchored to the power spectrum calculated
from the simulation, and find consistent results within \pm 1 sigma
fluctuations. These results show the importance of anchoring turbulence effects
on SN neutrinos to realistic, fine-grained SN models.Comment: 19 pages, 8 figures (Major changes in the text, references added,
analysis and figures improved, main results unchanged. To appear in JCAP.
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