105 research outputs found
Potential for Supernova Neutrino Detection in MiniBooNE
The MiniBooNE detector at Fermilab is designed to search for oscillation appearance at and to make a
decisive test of the LSND signal. The main detector (inside a veto shield) is a
spherical volume containing 0.680 ktons of mineral oil. This inner volume,
viewed by 1280 phototubes, is primarily a \v{C}erenkov medium, as the
scintillation yield is low. The entire detector is under a 3 m earth
overburden. Though the detector is not optimized for low-energy (tens of MeV)
events, and the cosmic-ray muon rate is high (10 kHz), we show that MiniBooNE
can function as a useful supernova neutrino detector. Simple trigger-level cuts
can greatly reduce the backgrounds due to cosmic-ray muons. For a canonical
Galactic supernova at 10 kpc, about 190 supernova
events would be detected. By adding MiniBooNE to the international network of
supernova detectors, the possibility of a supernova being missed would be
reduced. Additionally, the paths of the supernova neutrinos through Earth will
be different for MiniBooNE and other detectors, thus allowing tests of
matter-affected mixing effects on the neutrino signal.Comment: Added references, version to appear in PR
Detection of Supernova Neutrinos by Neutrino-Proton Elastic Scattering
We propose that neutrino-proton elastic scattering, ,
can be used for the detection of supernova neutrinos in scintillator detectors.
Though the proton recoil kinetic energy spectrum is soft, with , and the scintillation light output from slow, heavily ionizing
protons is quenched, the yield above a realistic threshold is nearly as large
as that from . In addition, the measured proton
spectrum is related to the incident neutrino spectrum, which solves a
long-standing problem of how to separately measure the total energy and
temperature of , , , and .
The ability to detect this signal would give detectors like KamLAND and
Borexino a crucial and unique role in the quest to detect supernova neutrinos.Comment: 10 pages, 9 figures, revtex
Bounds on neutrino magnetic moment tensor from solar neutrinos
Solar neutrinos with non-zero magnetic moments will contribute to the
electron scattering rates in the Super-Kamiokande experiment. The magnetic
moment scattering events in Super-K can be accommodated in the standard VO or
MSW solutions by a change of the parameter space of mass square difference and
mixing angle-but the shifted neutrino parameters obtained from Super-K will
(for some values of neutrino magnetic moments) become incompatible with the
fits from SNO, Gallium and Chlorine experiments. We compute the upper bounds on
the Dirac and Majorana magnetic moments of solar neutrinos by simultaneously
fitting all the observed solar neutrino rates. The bounds the magnetic moment
matrix elements are of the order of 10^{-10} Bohr magnetron.Comment: 9 pages latex file with 6 figures; References added, typos corrected,
matches version to appear in Phys Rev
Can a supernova be located by its neutrinos?
A future core-collapse supernova in our Galaxy will be detected by several
neutrino detectors around the world. The neutrinos escape from the supernova
core over several seconds from the time of collapse, unlike the electromagnetic
radiation, emitted from the envelope, which is delayed by a time of order
hours. In addition, the electromagnetic radiation can be obscured by dust in
the intervening interstellar space. The question therefore arises whether a
supernova can be located by its neutrinos alone. The early warning of a
supernova and its location might allow greatly improved astronomical
observations. The theme of the present work is a careful and realistic
assessment of this question, taking into account the statistical significance
of the various neutrino signals. Not surprisingly, neutrino-electron forward
scattering leads to a good determination of the supernova direction, even in
the presence of the large and nearly isotropic background from other reactions.
Even with the most pessimistic background assumptions, SuperKamiokande (SK) and
the Sudbury Neutrino Observatory (SNO) can restrict the supernova direction to
be within circles of radius and , respectively. Other
reactions with more events but weaker angular dependence are much less useful
for locating the supernova. Finally, there is the oft-discussed possibility of
triangulation, i.e., determination of the supernova direction based on an
arrival time delay between different detectors. Given the expected statistics
we show that, contrary to previous estimates, this technique does not allow a
good determination of the supernova direction.Comment: 11 pages including 2 figures. Revised version corrects typos, adds
some brief comment
The angular distribution of the reaction
The reaction is very important for low-energy
( MeV) antineutrino experiments. In this paper we calculate
the positron angular distribution, which at low energies is slightly backward.
We show that weak magnetism and recoil corrections have a large effect on the
angular distribution, making it isotropic at about 15 MeV and slightly forward
at higher energies. We also show that the behavior of the cross section and the
angular distribution can be well-understood analytically for MeV by calculating to , where is the nucleon mass. The
correct angular distribution is useful for separating events from other reactions and detector backgrounds, as well as for
possible localization of the source (e.g., a supernova) direction. We comment
on how similar corrections appear for the lepton angular distributions in the
deuteron breakup reactions and . Finally, in the reaction , the
angular distribution of the outgoing neutrons is strongly forward-peaked,
leading to a measurable separation in positron and neutron detection points,
also potentially useful for rejecting backgrounds or locating the source
direction.Comment: 10 pages, including 5 figure
Charged-current neutrino-208Pb reactions
We present theoretical results on the non flux-averaged
and
reaction cross sections, obtained within the charge-exchange
Random-Phase-Approximation. A detailed knowledge of these cross sections is
important in different contexts. In particular, it is necessary to assess the
possibility of using lead as a detector in future experiments on supernova
neutrinos, such as OMNIS and LAND, and eventually detect neutrino oscillation
signals by exploiting the spectroscopic properties of . We discuss
the present status on the theoretical predictions of the reaction cross
sections.Comment: 5 pages, latex, 3 figures. added discussion on present status,
Submitted to Phys.Rev.
Supernova Neutrinos and the LSND Evidence for Neutrino Oscillations
The observation of the energy spectrum from a supernova burst
can provide constraints on neutrino oscillations. We derive formulas for
adiabatic oscillations of supernova antineutrinos for a variety of 3- and
4-neutrino mixing schemes and mass hierarchies which are consistent with the
LSND evidence for oscillations.
Finally, we explore the constraints on these models and LSND given by the
supernova SN1987A 's observed by the Kamiokande-2 and IMB-3
detectors.Comment: 8 pages, 3 figures. Changes with respect to original version:
appendix added; minor changes in text, figures, reference
Neutrino Observatories Can Characterize Cosmic Sources and Neutrino Properties
Neutrino telescopes that measure relative fluxes of ultrahigh-energy
can give information about the location and
characteristics of sources, about neutrino mixing, and can test for neutrino
instability and for departures from CPT invariance in the neutrino sector. We
investigate consequences of neutrino mixing for the neutrino flux arriving at
Earth, and consider how terrestrial measurements can characterize distant
sources. We contrast mixtures that arise from neutrino oscillations with those
signaling neutrino decays. We stress the importance of measuring fluxes in neutrino observatories.Comment: 9 RevTeX pages, 4 figure
Sensitivity on Earth Core and Mantle densities using Atmospheric Neutrinos
Neutrino radiography may provide an alternative tool to study the very deep
structures of the Earth. Though these measurements are unable to resolve the
fine density layer features, nevertheless the information which can be obtained
are independent and complementary to the more conventional seismic studies. The
aim of this paper is to assess how well the core and mantle averaged densities
can be reconstructed through atmospheric neutrino radiography. We find that
about a 2% sensitivity for the mantle and 5% for the core could be achieved for
a ten year data taking at an underwater km^3 Neutrino Telescope. This result
does not take into account systematics related to the details of the
experimental apparatus.Comment: 11 pages, 11 figures, accepted for publication in JCA
CPT Violation and the Nature of Neutrinos
In order to accommodate the neutrino oscillation signals from the solar,
atmospheric, and LSND data, a sterile fourth neutrino is generally invoked,
though the fits to the data are becoming more and more constrained. However, it
has recently been shown that the data can be explained with only three
neutrinos, if one invokes CPT violation to allow different masses and mixing
angles for neutrinos and antineutrinos. We explore the nature of neutrinos in
such CPT-violating scenarios. Majorana neutrino masses are allowed, but in
general, there are no longer Majorana neutrinos in the conventional sense.
However, CPT-violating models still have interesting consequences for
neutrinoless double beta decay. Compared to the usual case, while the larger
mass scale (from LSND) may appear, a greater degree of suppression can also
occur.Comment: 10 pages, 1 figur
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