8 research outputs found
Collective neutrino flavor transitions in supernovae and the role of trajectory averaging
Non-linear effects on supernova neutrino oscillations, associated with
neutrino self-interactions, are known to induce collective flavor transitions
near the supernova core for theta_13 \neq 0. In scenarios with very shallow
electron density profiles, these transformations have been shown to couple with
ordinary matter effects, jointly producing spectral distortions both in normal
and inverted hierarchy. In this work we consider a complementary scenario,
characterized by higher electron density, as indicated by post-bounce
shock-wave simulations. In this case, early collective flavor transitions are
decoupled from later, ordinary matter effects. Moreover, such transitions
become more amenable to both numerical computations and analytical
interpretations in inverted hierarchy, while they basically vanish in normal
hierarchy. We numerically evolve the neutrino density matrix in the region
relevant for self-interaction effects. In the approximation of averaged
intersection angle between neutrino trajectories, our simulations neatly show
the collective phenomena of synchronization, bipolar oscillations, and spectral
split, recently discussed in the literature. In the more realistic (but
computationally demanding) case of non-averaged neutrino trajectories, our
simulations do not show new significant features, apart from the smearing of
``fine structures'' such as bipolar nutations. Our results seem to suggest
that, at least for non-shallow matter density profiles, averaging over neutrino
trajectories plays a minor role in the final outcome. In this case, the swap of
nu_e and nu_{\mu,\tau} spectra above a critical energy may represent an
unmistakable signature of the inverted hierarchy, especially for theta_{13}
small enough to render further matter effects irrelevant.Comment: v2 (27 pages, including 9 eps figures). Typos removed, references
updated. Minor comments added. Corrected numerical errors in Eq.(6). Matches
the published versio
Mini Z' Burst from Relic Supernova Neutrinos and Late Neutrino Masses
In models in which neutrinos are light, due to a low scale of symmetry
breaking, additional light bosons are generically present. We show that the
interaction between diffuse relic supernova neutrinos (RSN) and the cosmic
background neutrinos, via exchange of these light scalars, can result in a
dramatic change of the supernova (SN) neutrinos flux. Measurement of this
effect with current or future experiments can provide a spectacular direct
evidence for the low scale models. We demonstrate how the observation of
neutrinos from SN1987A constrains the symmetry breaking scale of the above
models. We also discuss how current and future experiments may confirm or
further constrain the above models, either by detecting the ``accumulative
resonance'' that diffuse RSN go through or via a large suppression of the flux
of neutrinos from nearby < O(Mpc) SN bursts.Comment: 24 pages, 8 figures, version to be published in JHE
Supernova Neutrino-Nucleus Astrophysics
In this brief review we explore the role of neutrino-nucleus interactions in
core-collapse supernovae and discuss open questions. In addition implications
of neutrino mass and mixings in such environments are summarized.Comment: Revtex 4 figure
Damping of supernova neutrino transitions in stochastic shock-wave density profiles
Supernova neutrino flavor transitions during the shock wave propagation are
known to encode relevant information not only about the matter density profile
but also about unknown neutrino properties, such as the mass hierarchy (normal
or inverted) and the mixing angle theta_13. While previous studies have
focussed on "deterministic" density profiles, we investigate the effect of
possible stochastic matter density fluctuations in the wake of supernova shock
waves. In particular, we study the impact of small-scale fluctuations on the
electron (anti)neutrino survival probability, and on the observable spectra of
inverse-beta-decay events in future water-Cherenkov detectors. We find that
such fluctuations, even with relatively small amplitudes, can have significant
damping effects on the flavor transition pattern, and can partly erase the
shock-wave imprint on the observable time spectra, especially for
sin^2(theta_13) > O(10^-3).Comment: v2 (23 pages, including 6 eps figures). Typos removed, references
updated, matches the published versio
Effect of Collective Flavor Oscillations on the Diffuse Supernova Neutrino Background
Collective flavor oscillations driven by neutrino-neutrino self interaction
inside core-collapse supernovae have now been shown to bring drastic changes in
the resultant neutrino fluxes. This would in turn significantly affect the
diffuse supernova neutrino background (DSNB), created by all core-collapse
supernovae that have exploded in the past. In view of these collective effects,
we re-analyze the potential of detecting the DSNB in currently running and
planned large-scale detectors meant for detecting both electron neutrinos and
antineutrinos. The next generation detectors should be able to observe DSNB
fluxes. Under certain conducive conditions, one could learn about neutrino
parameters. For instance, it might be possible to determine the neutrino mass
hierarchy, even if theta_{13} is almost zero.Comment: Ver3 (24 pages, 4 figures and 4 tables): Reference added. Figure 1
corrected. Misprints corrected. Acknowledgment added. No changes in results.
Supercedes the version published in JCA
Large underground, liquid based detectors for astro-particle physics in Europe: scientific case and prospects
This document reports on a series of experimental and theoretical studies
conducted to assess the astro-particle physics potential of three future
large-scale particle detectors proposed in Europe as next generation
underground observatories. The proposed apparatus employ three different and,
to some extent, complementary detection techniques: GLACIER (liquid Argon TPC),
LENA (liquid scintillator) and MEMPHYS (\WC), based on the use of large mass of
liquids as active detection media. The results of these studies are presented
along with a critical discussion of the performance attainable by the three
proposed approaches coupled to existing or planned underground laboratories, in
relation to open and outstanding physics issues such as the search for matter
instability, the detection of astrophysical- and geo-neutrinos and to the
possible use of these detectors in future high-intensity neutrino beams.Comment: 50 pages, 26 figure
Symmetries in collective neutrino oscillations
We discuss the relationship between a symmetry in the neutrino flavour
evolution equations and neutrino flavour oscillations in the collective
precession mode. This collective precession mode can give rise to spectral
swaps (splits) when conditions can be approximated as homogeneous and
isotropic. Multi-angle numerical simulations of supernova neutrino flavour
transformation show that when this approximation breaks down, non-collective
neutrino oscillation modes decohere kinematically, but the collective
precession mode still is expected to stand out. We provide a criterion for
significant flavour transformation to occur if neutrinos participate in a
collective precession mode. This criterion can be used to understand the
suppression of collective neutrino oscillations in anisotropic environments in
the presence of a high matter density. This criterion is also useful in
understanding the breakdown of the collective precession mode when neutrino
densities are small.Comment: 21 pages, 2 figures. Significant revision in presentation with a new
title in v
Science from detection of neutrinos from supernovae
The neutrinos emitted from supernovae contain information about the physics of stellar collapse and of the nature of the neutrinos themselves. Several large detectors exist that will be capable of observing some subset of those neutrinos. In addition, we have designed OMNIS, the Observatory for Multiflavour NeutrInos from Supernovae. OMNIS will detect the neutrinos from (a) neutral-current interactions from νe, νµ, ν̄µ, ντ and ν̄τ, and (b) charged-current interactions from high-momentum νe, with lead nuclei. It will utilize two types of detectors: (1) lead slabs alternating with vertical planes of neutron detectors, in which neutrons produced by neutrino–lead interactions will be detected, and (2) lead perchlorate, in which both the resulting neutrons and Cerenkov light will be detected. OMNIS will measure neutrino masses below 100 eV, provide new information on MSW or vacuum oscillations from νµ/ντ to νe, especially to 13, and possibly diagnose the process of collapse to a black hole. It will observe the late-time evolution of the neutrino distributions, and possibly se