953 research outputs found
Dark Matter Detection With Electron Neutrinos in Liquid Scintillation Detectors
We consider the prospects for liquid scintillation experiments (with a focus
on KamLAND) to detect the flux of electron neutrinos arising from dark matter
annihilation in the core of the sun. We show that, with data already taken,
KamLAND can provide the greatest sensitivity to the dark matter-proton
spin-dependent scattering cross-section for dark matter lighter than 20 GeV. It
is also possible to probe the dark matter-nucleon spin-independent scattering
cross-section for isospin-violating dark matter lighter than 10 GeV. KamLAND
can thus potentially confirm the dark matter interpretation of the DAMA and
CoGeNT signals, utilizing data already taken.Comment: 5 pages, 4 figures, PDFLaTeX; v2: references added, figures updated,
more detailed comparison of liquid scintillation and water Cerenkov detectors
(journal version
Astrophysical tau neutrinos and their detection by large neutrino telescopes
We present results of the detailed Monte Carlo calculation of the rates of
double-bang events in 1 km underwater neutrino telescope with taking into
account the effects of -neutrino propagation through the Earth. As an
input, the moderately optimistic theoretical predictions for diffuse neutrino
spectra of AGN jets are used.Comment: Talk given at the NANP'03 conference, June 2003. 4 pages, one eps
figur
Light Dark Matter Detection Prospects at Neutrino Experiments
We consider the prospects for the detection of relatively light dark matter
through direct annihilation to neutrinos. We specifically focus on the
detection possibilities of water Cherenkov and liquid scintillator neutrino
detection devices. We find in particular that liquid scintillator detectors may
potentially provide excellent detection prospects for dark matter in the 4-10
GeV mass range. These experiments can provide excellent corroborative checks of
the DAMA/LIBRA annual modulation signal, but may yield results for low mass
dark matter in any case. We identify important tests of the ratio of electron
to muon neutrino events (and neutrino versus anti-neutrino events), which
discriminate against background atmospheric neutrinos. In addition, the
fraction of events which arise from muon neutrinos or anti-neutrinos (
and ) can potentially yield information about the branching
fractions of hypothetical dark matter annihilations into different neutrino
flavors. These results apply to neutrinos from secondary and tertiary decays as
well, but will suffer from decreased detectability.Comment: 13 pages, 2 figures, pdflatex, references, one figure and comments on
electron neutrino bounds and on spin-dependent scattering limits added.
Figures updated
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
Signatures of Nucleon Disappearance in Large Underground Detectors
For neutrons bound inside nuclei, baryon instability can manifest itself as a
decay into undetectable particles (e.g., ), i.e.,
as a disappearance of a neutron from its nuclear state. If electric charge is
conserved, a similar disappearance is impossible for a proton. The existing
experimental lifetime limit for neutron disappearance is 4-7 orders of
magnitude lower than the lifetime limits with detectable nucleon decay products
in the final state [PDG2000]. In this paper we calculated the spectrum of
nuclear de-excitations that would result from the disappearance of a neutron or
two neutrons from C. We found that some de-excitation modes have
signatures that are advantageous for detection in the modern high-mass,
low-background, and low-threshold underground detectors, where neutron
disappearance would result in a characteristic sequence of time- and
space-correlated events. Thus, in the KamLAND detector [Kamland], a
time-correlated triple coincidence of a prompt signal, a captured neutron, and
a decay of the residual nucleus, all originating from the same
point in the detector, will be a unique signal of neutron disappearance
allowing searches for baryon instability with sensitivity 3-4 orders of
magnitude beyond the present experimental limits.Comment: 13 pages including 6 figures, revised version, to be published in
Phys.Rev.
Neutrinos from galactic sources of cosmic rays with known gamma-ray spectra
We describe a simple procedure to estimate the high-energy neutrino flux from
the observed gamma-ray spectra of galactic cosmic ray sources that are
transparent to their gamma radiation. We evaluate in this way the neutrino flux
from the supernova remnant RX J1713.7-3946, whose very high-energy gamma-ray
spectrum (assumed to be of hadronic origin) is not a power law distribution
according to H.E.S.S. observations. The corresponding muon signal in neutrino
telescopes is found to be about 5 events per square kilometer per year in an
ideal detector.Comment: 6 pages, 1 figure; accepted in Astroparticle Physic
Background light measurements at the DUMAND site
Ambient light intensities at the DUMAND site, west of the island of Hawaii were measured around the one photoelectron level. Throughout the water column between 1,500m and 4,700m, a substantial amount of stimulateable bioluminescence is observed with a ship suspended detector. But non-stimulated bioluminescence level is comparable, or less than, K sup 40 background, when measured with a bottom tethered detector typical of a DUMAND optical module
TeV gamma-UHECR anisotropy by decaying nuclei in flight: first neutrino traces?
Ultra High Cosmic Rays) made by He-like lightest nuclei might solve the AUGER
extragalactic clustering along Cen A. Moreover He like UHECR nuclei cannot
arrive from Virgo because the light nuclei fragility and opacity above a few
Mpc, explaining the Virgo UHECR absence. UHECR signals are spreading along
Cen-A as observed because horizontal galactic arms magnetic fields, bending
them on vertical angles. Cen A events by He-like nuclei are deflected as much
as the observed clustered ones; proton will be more collimated while heavy
(iron) nuclei are too much dispersed. Such a light nuclei UHECR component
coexist with the other Auger heavy nuclei and with the Hires nucleon
composition. Remaining UHECR spread group may hint for correlations with other
gamma (MeV-Al^{26} radioactive) maps, mainly due to galactic SNR sources as
Vela pulsar, the brightest, nearest GeV source. Other nearest galactic gamma
sources show links with UHECR via TeV correlated maps. We suggest that UHECR
are also heavy radioactive galactic nuclei as Ni^{56}, Ni^{57} and Co^{60}
widely bent by galactic fields. UHECR radioactivity (in and
channels) and decay in flight at hundreds keV is boosted (by huge Lorentz
factor (nearly a billion) leading to PeVs electrons and consequent synchrotron
TeVs gamma offering UHECR-TeV correlated sky anisotropy. Moreover also rarest
and non-atmospheric electron and tau neutrinos secondaries at PeVs, as the
first two rarest shower just discovered in ICECUBE, maybe the first signature
of such expected radioactive secondary tail.Comment: 7 pages,3 figures. arXiv admin note: substantial text overlap with
arXiv:1201.015
Neutrino Decay as an Explanation of Atmospheric Neutrino Observations
We show that the observed zenith angle dependence of the atmospheric
neutrinos can be accounted for by neutrino decay. Furthermore, it is possible
to account for all neutrino anomalies with just three flavors.Comment: 4 pages, 1 figur
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