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John G. Learned

Publications and source records attributed to John G. Learned.

35 records · Page 2Linked to original sources
arXiv2013

Theoretical Antineutrino Detection, Direction and Ranging at Long Distances

In this paper we introduce the concept of what we call "NUDAR" (NeUtrino Direction and Ranging), making the point that measurements of the observed energy and direction vectors can be employed to passively deduce the exact three-dimensional location and thermal power of geophysical and anthropogenic neutrino sources from even a single detector. We present the most precise background estimates to date, all handled in full three dimensions, as functions of depth and geographical location. For the present calculations, we consider a hypothetical 138 kiloton detector which can be transported to an ocean site and deployed to an operational depth. We present a Bayesian estimation framework to incorporate any a priori knowledge of the reactor that we are trying to detect, as well as the estimated uncertainty in the background and the oscillation parameters. Most importantly, we fully employ the knowledge of the reactor spectrum and the distance-dependent effects of neutrino oscillations on such spectra. The latter, in particular, makes possible determination of range from one location, given adequate signal statistics. Further, we explore the rich potential of improving detection with even modest improvements in individual neutrino direction determination. We conclude that a 300 MWth reactor can indeed be geolocated, and its operating power estimated with one or two detectors in the hundred kiloton class at ranges out to a few hundred kilometers. We note that such detectors would have natural and non-interfering utility for scientific studies of geo-neutrinos, neutrino oscillations, and astrophysical neutrinos. This motivates the development of cost effective methods of constructing and deploying such next generation detectors.

physics.ins-det↗
arXiv2012

The next-generation liquid-scintillator neutrino observatory LENA

We propose the liquid-scintillator detector LENA (Low Energy Neutrino Astronomy) as a next-generation neutrino observatory on the scale of 50 kt. The outstanding successes of the Borexino and KamLAND experiments demonstrate the large potential of liquid-scintillator detectors in low-energy neutrino physics. LENA's physics objectives comprise the observation of astrophysical and terrestrial neutrino sources as well as the investigation of neutrino oscillations. In the GeV energy range, the search for proton decay and long-baseline neutrino oscillation experiments complement the low-energy program. Based on the considerable expertise present in European and international research groups, the technical design is sufficiently mature to allow for an early start of detector realization.

astro-ph.IM↗
arXiv2011

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.

hep-ph↗
arXiv2010

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 ($R_μ$ and $R_{\bar μ}$) 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.

hep-ph↗
arXiv2009

High Energy Neutrino Physics with Liquid Scintillation Detectors

Large liquid scintillation detectors have been generally dedicated to low energy neutrino measurements, in the MeV energy region (as for example, KamLAND and Borexino). Herein we describe the potential employment of large detectors (>1 kiloton) for studies of higher energy neutrinos interactions, from the cosmic rays and as a long baseline neutrino detector. Generally when people have considered large new instruments such as Hanohano and LENA, they have abandoned the possibility of doing useful measurements with higher energy neutrino interactions since these produce enough light to illuminate every photomultiplier tube, and the scintillation light is isotropic. Here we take into account Fermat's principle, which tells us that indeed the first light to reach the PMTs will be on or near the lightcone, the "Fermat surface", and that directional track information is available. Moreover we have realized that particle type distinction is possible (quasi-elastic muons from electrons). In fact the resolution from a detector of comparable size to SuperKamiokande, may be better in both angle, energy and possibly particle type. This realization opens the doors to a number of applications. Moreover, this capability can be demonstrated with the use of (future) KamLAND detected events in the new long baseline neutrino beam from the Jaeri accelerator in Japan, due to start operations this year. Some of the most attractive possibilities for the future may be in using Hanohano as a movable long baseline detector in this same beam, the employment of LENA in Europe in future long baseline neutrino beams from CERN, and in the DUSEL underground laboratory at Homestake.

hep-ex↗
arXiv2008

Galactic Neutrino Communication

We examine the possibility to employ neutrinos to communicate within the galaxy. We discuss various issues associated with transmission and reception, and suggest that the resonant neutrino energy near 6.3 PeV may be most appropriate. In one scheme we propose to make Z^o particles in an overtaking e^+ - e^- collider such that the resulting decay neutrinos are near the W^- resonance on electrons in the laboratory. Information is encoded via time structure of the beam. In another scheme we propose to use a 30 PeV pion accelerator to create neutrino or anti-neutrino beams. The latter encodes information via the particle/anti-particle content of the beam, as well as timing. Moreover, the latter beam requires far less power, and can be accomplished with presently foreseeable technology. Such signals from an advanced civilization, should they exist, will be eminently detectable in neutrino detectors now under construction.

physics.pop-ph↗
arXiv2008

Hanohano: A Deep Ocean Anti-Neutrino Detector for Unique Neutrino Physics and Geophysics Studies

The science potential of a 10 kiloton deep-ocean liquid scintillation detector for ~1 MeV energy scale electron anti-neutrinos has been studied. Such an instrument, designed to be portable and function in the deep ocean (3-5 km) can make unique measurements of the anti-neutrinos from radioactive decays in the Earth'.s mantle. Ths information speaks to some of the most fundamental questions in geology about the origin of the Earth, plat e tectonics, the geomagnetic field and even somewhat indirectly to global warming. Measurements in multiple locations will strengthen the potential insights. On the particle physics side, we have identified a unique role in the study of anti-neutrinos from a nuclear power complex, at a range of 55-60 km off shore. Not only can precision measurements be made of most neutrino mixing parameters, including $θ_{13}$ (depending on magnitude), but the neutrino mass hierarchy can be determined in a method not heretofore discussed, and one which does not rely upon matter effects. This detector is under active study on paper, in the laboratory, and at sea. An interdisciplinary and international collaboration is in formation, and plans are in motion for a major proposal, to be followed by construction over several years.

hep-ex↗
arXiv2008

Detection of Geoneutrinos: Can We Make the Gnus Work for Us?

The detection of electron anti-neutrinos from natural radioactivity in the earth has been a goal of neutrino researchers for about half a century. It was accomplished by the KamLAND Collaboration in 2005, and opens the way towards studies of the Earth's radioactive content, with very important implications for geology. New detectors are operating (KamLAND and Borexino), building (SNO+) and being proposed (Hanohano, LENA, Earth and others) that will go beyond the initial observation and allow interesting geophysical and geochemical research, in a means not otherwise possible. Herein we describe the approaches being taken (large liquid scintillation instruments), the experimental and technical challenges (optical detectors, directionality), and prospects for growth of this field. There is related spinoff in particle physics (neutrino oscillations and hierarchy determination), astrophysics (solar neutrinos, supernovae, exotica), and in the practical matter of remote monitoring of nuclear reactors.

physics.geo-ph↗
arXiv2008

The Cepheid Galactic Internet

We propose that a sufficiently advanced civilization may employ Cepheid variable stars as beacons to transmit all-call information throughout the galaxy and beyond. One can construct many scenarios wherein it would be desirable for such a civilization of star ticklers to transmit data to anyone else within viewing range. The beauty of employing Cepheids is that these stars can be seen from afar(we monitor them out through the Virgo cluster), and any developing technological society would seem to be likely to closely observe them as distance markers. Records exist of Cepheids for well over one hundred years. We propose that these (and other regularly variable types of stars) be searched for signs of phase modulation (in the regime of short pulse duration) and patterns, which could be indicative of intentional signaling.

astro-ph↗
arXiv2004

Pseudo-Dirac Neutrinos, a Challenge for Neutrino Telescopes

Neutrinos may be pseudo-Dirac states, such that each generation is actually composed of two maximally-mixed Majorana neutrinos separated by a tiny mass difference. The usual active neutrino oscillation phenomenology would be unaltered if the pseudo-Dirac splittings are $δm^2 \alt 10^{-12}$ eV$^2$; in addition, neutrinoless double beta decay would be highly suppressed. However, it may be possible to distinguish pseudo-Dirac from Dirac neutrinos using high-energy astrophysical neutrinos. By measuring flavor ratios as a function of $L/E$, mass-squared differences down to $δm^2 \sim 10^{-18}$ eV$^2$ can be reached. We comment on the possibility of probing cosmological parameters with neutrinos.

hep-ph↗
arXiv2000

The Atmospheric Neutrino Anomaly: Muon Neutrino Disappearance

With the 1998 announcement of new evidence for muon neutrino disappearance observed by the Super-Kamiokande experiment, the more than a decade old atmospheric neutrino anomaly moved from a possible indication for neutrino oscillations to an almost inescapable implication. The evidence from all experiments is reviewed, and indications are presented that the oscillations are probably between muon and tau neutrinos with nearly maximal mixing. Implications and future directions in neutrino oscillations research are discussed.

hep-ex↗
arXiv1999

The sun as a high energy neutrino source

Cosmic ray interactions in the solar atmosphere yield a flux of electron and muon neutrinos with energies greater than 10 GeV. We discuss the influence of neutrino oscillations on the event rates in water-based Cerenkov detectors due to this neutrino flux and comment on the possibility of detecting the sun as a high energy neutrino source.

astro-ph↗
arXiv1997

Up-Down Asymmetry: A Diagnostic for Neutrino Oscillations

We propose a simple test of underground neutrino data to discriminate amongst neutrino oscillation models. It uses the asymmetry between downward-going events and upward-going events, for electron and muon events separately. Because of the symmetry of typical underground detectors, an asymmetry can be compared with calculations with little need for the intermediary of a simulation program. Furthermore, we show that the various oscillation scenarios give rise to dramatically differing trajectories of asymmetry versus energy for muons and electrons. This permits a clean distinction to be drawn between models.

hep-ph↗
arXiv1995

Progress and Prospects in Neutrino Astrophysics

The neutrino deficits observed in four solar neutrino experiments, relative to the theoretical predictions, have led to fresh insights into neutrino and solar physics. Neutrino emission from distant, energetic astronomical systems may form the basis for a new field of astronomy. Additional experiments are needed to test explanations of the solar neutrino deficits and to allow the detection of more distant sources.

astro-ph↗
arXiv1994

Detecting Nutau Oscillations as PeV Energies

It is suggested that a large deep underocean neutrino detector, given the presence of significant numbers of neutrinos in the PeV range as predicted by various models of Active Galactic Nuclei, can make unique measurements of the properties of neutrinos. It will be possible to observe the existence of the nu_tau, measure its mixing with other flavors, in fact test the mixing pattern for all three flavors based upon the mixing parameters suggested by the atmospheric and solar neutrino data, and measure the nu_tau cross section. The key signature is the charged current nu_tau interaction, which produces a double cascade, one at either end of a minimum ionizing track. At a few PeV these cascades would be separated by roughly 100 m, and thus be easily resolvable in DUMAND and similar detectors. Future applications are precise neutrino astronomy and earth tomography.

hep-ph↗