Potential for Supernova Neutrino Detection in MiniBooNE

The MiniBooNE detector at Fermilab is designed to search for $\nu_\mu \to \nu_e$ oscillation appearance at $E_\nu \sim 1 {\rm GeV}$ 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 $\bar{\nu}_e + p \to e^+ + n$ 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, $\nu + p \to \nu + p$, can be used for the detection of supernova neutrinos in scintillator detectors. Though the proton recoil kinetic energy spectrum is soft, with $T_p \simeq 2 E_\nu^2/M_p$, 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 $\bar{\nu}_e + p \to e^+ + n$. 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 $\nu_\mu$, $\nu_\tau$, $\bar{\nu}_\mu$, and $\bar{\nu}_\tau$. 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 $5^\circ$ and $20^\circ$, 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 νˉe+p→e++n\bar{\nu}_e + p \to e^+ + n

The reaction $\bar{\nu}_e + p \to e^+ + n$ is very important for low-energy ($E_\nu \lesssim 60$ 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 $E_\nu \lesssim 60$ MeV by calculating to ${\cal O}(1/M)$, where $M$ is the nucleon mass. The correct angular distribution is useful for separating $\bar{\nu}_e + p \to e^+ + n$ 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 $\bar{\nu}_e + d \to e^+ + n + n$ and $\nu_e + d \to e^- + p + p$. Finally, in the reaction $\bar{\nu}_e + p \to e^+ + n$, 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 $^{208}Pb(\nu_{e},e^-)^{208}Bi$ and $^{208}Pb(\nu_{\mu},\mu^-)^{208}Bi$ 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 $^{208}Bi$. 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 $\bar{\nu}_e$ 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 $\bar{\nu}_{\mu}\to \bar{\nu}_e$ oscillations. Finally, we explore the constraints on these models and LSND given by the supernova SN1987A $\bar{\nu}_e$'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 $\nu_{e}, \nu_{\mu}, \nu_{\tau}$ 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

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