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

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

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

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

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

Studies of MCP-PMTs in the miniTimeCube neutrino detector

This report highlights two different types of cross-talk in the photodetectors of the miniTimeCube neutrino experiment. The miniTimeCube detector has 24 $8 \times 8$-anode Photonis MCP-PMTs Planacon XP85012, totalling 1536 individual pixels viewing the 2-liter cube of plastic scintillator

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.

Fate of the Sterile Neutrino

In light of recent Super-Kamiokande data and global fits that seem to exclude both pure \nu_\mu \to \nu_s oscillations of atmospheric neutrinos and pure \nu_e \to \nu_s oscillations of solar neutrinos (where \nu_s is a sterile neutrino), we reconsider four-neutrino models to explain the LSND, atmospheric, and solar neutrino oscillation indications. We argue that the solar data, with the exception of the ^{37}Cl results, are suggestive of \nu_e \to \nu_s oscillations that average to a probability of approximately 1/2. In this interpretation, with two pairs of nearly degenerate mass eigenstates separated by order 1 eV, the day-night asymmetry, seasonal dependence, and energy dependence for ^8B neutrinos should be small. Alternatively, we find that four-neutrino models with one mass eigenstate widely separated from the others (and with small sterile mixings to active neutrinos) may now be acceptable in light of recently updated LSND results; the ^{37}Cl data can be accommodated in this model. For each scenario, we present simple four-neutrino mixing matrices that fit the stated criterion and discuss future tests

Prospects for observations of high-energy cosmic tau neutrinos

We study prospects for the observations of high-energy cosmic tau neutrinos (E \geq 10^6 GeV) originating from proton acceleration in the cores of active galactic nuclei. We consider the possibility that vacuum flavor neutrino oscillations induce a tau to muon neutrino flux ratio greatly exceeding the rather small value expected from intrinsic production. The criterias and event rates for under water/ice light Cerenkov neutrino telescopes are given by considering the possible detection of downgoing high-energy cosmic tau neutrinos through characteristic double shower events.Comment: 10 pages, Revtex, 3 figures included with eps