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$^3$ underwater neutrino telescope with taking into account the effects of $\tau$-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 ($R_{\mu}$ and $R_{\bar \mu}$) 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 $\nu_{e}, \nu_{\mu}, \nu_{\tau}$ 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 $\nu_{e}, \nu_{\mu}, \nu_{\tau}$ 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., $\it n \to \nu \nu \bar{\nu}$), 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 $^{12}$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 $\beta^{+}$ 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 $\beta$ and $\gamma$ 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