Large Neutrino Detectors Research Articles

High energy neutrinos from dissipative photospheric models of gamma ray bursts

We calculate the high energy neutrino spectrum from gamma-raybursts where the emission arises in a dissipative jet photosphere determined byeither baryonically or magnetically dominated dynamics, and compare theseneutrino spectra to those obtained in conventional internal shock models. Wealso calculate the diffuse neutrino spectra based on these models, which appearcompatible with the current IceCube 40+59 constraints. While a re-analysisbased on the models discussed here and the data from the full array would beneeded, it appears that only those models with the most extreme parameters areclose to being constrained at present. A multi-year operation of the fullIceCube and perhaps a next generation of large volume neutrino detectors may berequired in order to distinguish between the various models discussed.

40Ar(n,p)40Cl reaction cross section between 9 and 15 MeV

The activation technique was used to measure the cross section for the reaction ${}^{40}\mathrm{Ar}(n,\phantom{\rule{-0.16em}{0ex}}p){\phantom{\rule{0.16em}{0ex}}}^{40}\mathrm{Cl}$ in 0.5 MeV energy steps in the neutron energy range between 9 and 15 MeV. These data are important for estimating background contributions in neutrinoless double-beta decay and dark matter searches, as well as in argon-based large neutrino detectors. The data are compared to evaluations and theoretical predictions.

Gamma-ray bursts and their links with supernovae and cosmology

Gamma-ray bursts are the most luminous explosions in the Universe, whose origin and mechanism are the focus of intense interest. They appear connected to supernova remnants from massive stars or the merger of their remnants, and their brightness makes them temporarily detectable out to the largest distances yet explored in the universe. After pioneering breakthroughs from space and ground experiments, their study is entering a new phase with observations from the recently launched Fermi satellite, as well as the prospect of detections or limits from large neutrino and gravitational wave detectors. The interplay between such observations and theoretical models of gamma-ray bursts is reviewed, as well as their connections to supernovae and cosmology.

MicroBooNE and the Road to Large Liquid Argon Neutrino Detectors

Abstract Liquid Argon Time Projection Chambers (LArTPC's) provide a promising technology for multi-kiloton scale detectors aiming to address—among other pressing particle physics questions—the possibility of short and long baseline electron neutrino and antineutrino appearance. MicroBooNE, a 170 ton LArTPC under construction, is the next necessary step in a phased R&D effort toward construction and stable operation of larger-scale LArTPC's. This development effort also leans heavily on the ArgoNeuT and LAr1 LArTPC R&D experiments at Fermilab. In addition to advancing the LArTPC technology, these projects also provide unique physics opportunities. For example, Micro-BooNE will be located in the Booster Neutrino Beamline at Fermilab, at ∼470 m from neutrino production. Thus, in addition to measuring a suite of low energy neutrino cross sections on argon, MicroBooNE will investigate the anomalous low energy excess seen by the MiniBooNE experiment. Furthermore, the neutrino beam energy and relatively short baseline provide MicroBooNE with sensitivity to high-∼m2 neutrino oscillations. These proceedings summarize the role of the MicroBooNE detector in the US LArTPC R&D program, present its physics reach, and briefly discuss the physics potential of a dedicated near-future neutrino oscillation program at the Booster Neutrino Beamline, as a way to maximize the physics output of the Fermilab LArTPC R&D projects.

Observational limits of a large scale neutrino detector in a salt dome

We are investigating the possibility to construct a radio Askaryan neutrino observatory in a salt mine. The first step is to determine the optimal geometry such that the cost of experiment remains small but detection is still possible. For that we analyze the characteristics of the radio signal on its propagation from the site of the shower to a point where it intersects the radio antenna. We make a threshold analysis for such a detector, taking into account how the pulse couples to a realistic receiver. The signal-to-noise ratio limiting situation is also presented. In the end we calculate a single receiver effective volume.

Core-collapse astrophysics with a five-megaton neutrino detector

The legacy of solar neutrinos suggests that large neutrino detectors should be sited underground. However, to instead go underwater bypasses the need to move mountains, allowing much larger water Cherenkov detectors. We show that reaching a detector mass scale of ~5 Megatons, the size of the proposed Deep-TITAND, would permit observations of neutrino "mini-bursts" from supernovae in nearby galaxies on a roughly yearly basis, and we develop the immediate qualitative and quantitative consequences. Importantly, these mini-bursts would be detected over backgrounds without the need for optical evidence of the supernova, guaranteeing the beginning of time-domain MeV neutrino astronomy. The ability to identify, to the second, every core collapse in the local Universe would allow a continuous "death watch" of all stars within ~5 Mpc, making practical many previously-impossible tasks in probing rare outcomes and refining coordination of multi-wavelength/multi-particle observations and analysis. These include the abilities to promptly detect otherwise-invisible prompt black hole formation, provide advance warning for supernova shock-breakout searches, define tight time windows for gravitational-wave searches, and identify "supernova impostors" by the non-detection of neutrinos. Observations of many supernovae, even with low numbers of detected neutrinos, will help answer questions about supernovae that cannot be resolved with a single high-statistics event in the Milky Way.

IceCube's in-ice radio extension: Status and results

In 2006–2010, several radio frequency (RF) detectors and calibration equipment were deployed as part of the IceCube array at depths between 5 and 1400 m in preparation for a future large scale GZK neutrino detector. IceCube's deep holes and well-established data handling system provide a unique opportunity for deep-ice RF detection studies at the South Pole. We will present verification and calibration results as well as a status-review of ongoing analyses such as ice-properties, RF noise and reconstruction algorithms.

Tools and methods for simulation and evaluation of very large volume Cherenkov neutrino detectors

We report on the use of the HOU Reconstruction & Simulation (HOURS) software package in evaluating the performance of a Very Large Volume Neutrino Telescope. We present results of our study concerning the capability of a deep sea Cherenkov telescope in the Mediterranean Sea in detecting/discovering galactic and extragalactic high energy neutrino sources as well as measuring diffuse neutrino fluxes. Finally, we study a construction strategy of a large neutrino telescope that will lead to an early discovery of extragalactic neutrinos from gamma ray bursts.

Optical scattering lengths in large liquid-scintillator neutrino detectors

For liquid-scintillator neutrino detectors of kiloton scale, the transparency of the organic solvent is of central importance. The present paper reports on laboratory measurements of the optical scattering lengths of the organic solvents phenylxylylethane, linear alkylbenzene (LAB), and dodecane, which are under discussion for next-generation experiments such as SNO+ (Sudbury Neutrino Observatory), HanoHano, or LENA (Low Energy Neutrino Astronomy). Results comprise the wavelength range of 415-440 nm. The contributions from Rayleigh and Mie scattering as well as from absorption/re-emission processes are discussed. Based on the present results, LAB seems to be the preferred solvent for a large-volume detector.

Purification of lanthanides for large neutrino detectors: Thorium removal from gadolinium chloride

Metal-loaded liquid scintillators are the detectors of choice for various neutrino experiments. Procedures have been developed to transfer metals into organic liquids by solvent extraction or direct dissolution of a metallic compound. Traces of natural radioactivity introduced into the scintillator with the metal may produce undesirable backgrounds. Measurements using a 229Th tracer indicate that the inclusion of a pH-controlled partial hydrolysis and filtration prior to the preparation of a gadolinium-loading compound can reduce thorium by a factor of ∼100. This “self-scavenging” procedure has the advantage that it uses only reagents encountered in the production process. Addition of non-elemental scavengers such as iron, or the use of solvent extraction or ion exchange procedures can be avoided. It also improves the optical transmission in the blue region by removing traces of iron. This purification method has potential applications to the large-scale production of other metal-loaded liquid scintillators and for the removal of traces of thorium in the industrial production of lanthanides.

Cosmic ray positrons from annihilations into a new, heavy lepton

Recent results from the PAMELA experiment indicate an excess in the positron spectrum above 10 GeV, but antiproton data are consistent with the expected astrophysical backgrounds. We propose a scenario that reproduces these features. Dark matter annihilates through channels involving a new heavy vectorlike lepton which then decays by mixing with standard model leptons. If charged, this heavy lepton might be produced at the LHC, and could lead to multilepton final states or to long-lived charged tracks. Large neutrino detectors such as ANTARES or IceCube might be sensitive to a monochromatic neutrino line. This scenario may be simply embedded in various models, including an extension to the next-to-minimal supersymmetric standard model.

Search for Dark Matter with the ANTARES Neutrino Telescope

ANTARES (Astronomy with a Neutrino Telescope and Abyss environmental RESearch) is the largest neutrino detector currently operating in the Northern hemisphere. The detection principle relies on the observation of Cerenkov light emitted by muons resulting from charged current neutrino interactions in the water surrounding the detector and the seafloor below. The detector, which was completed in May 2008, consists of twelve lines (each housing 75 photomultipliers), placed at a depth of about 2480 meters 40 km off the coast of Toulon, France. The telescope is built to search for astrophysical neutrino point sources and for neutrinos created in self-annihilation of Dark-Matter particles. A likely source of such neutrino emission would be the Sun, where Dark Matter particles are expected to accumulate. Predictions of the neutrino flux originating from the Sun have been made based on the minimal Supergravity (mSugra) model including the effect of neutrino oscillations. Within mSugra the lightest supersymmetric particle, if a neutralino, is a possible candidate for cold Dark Matter. Using the general features of ANTARES in the energy range from 10 GeV to 400 GeV a prediction for exclusion limits for three years of datataking has been calculated.

Searches for diffuse astrophysical muon-neutrino fluxes with IceCube

The IceCube detector, located at the Amundsen-Scott South Pole station, is the largest neutrino detector ever constructed. It currently consists of 40 of the planned 80 strings -each instrumented with 60 optical modules between 1500 and 2500 metres depth in the clear Antarctic ice. One of the key searches is for a diffuse flux of high energy extraterrestrial neutrinos, in excess of that observed from cosmic-ray induced atmospheric neutrinos. To date, the best constraints on a diffuse flux come from IceCube's predecessor, AMANDA (Antarctic Muon And Neutrino Detector Array). The current focus is on analysis of the 2007 IceCube 22 string data, which will exceed the sensitivity of the integrated AMANDA exposure. Here we review the methodology and discuss the progress and status of the 22 string analysis.

The high-energy neutrino background from gamma-ray bursts

High-energy neutrinos from gamma-ray bursts (GRBs) have been expected in various scenarios. Many predictions for the prompt emission and afterglow emission were done in the pre-Swift era. In this paper, we see predictions of the high-energy neutrino emission in the Swift era. Recently, Swift has shown several novel phenomena such as flares, which allows new possibilities for the high-energy neutrino emission from GRBs. High-energy neutrino signals may be detected by future-coming large neutrino detectors such as IceCube and KM3Net. If detected, they are useful for revealing the nature of GRBs and connection between ultra-high-energy cosmic rays (UHECRs) and GRBs.

Searching for neutrinos from WIMP annihilations in the Galactic stellar disc

Weakly interacting massive particles (WIMPs) are a viable candidate for the relic abundance of dark matter (DM) produced in the early universe. So far WIMPs have eluded direct detection through interactions with baryonic matter. Neutrino emission from accumulated WIMP annihilations in the solar core has been proposed as a signature of DM, but has not yet been detected. These null results may be due to small scale DM density fluctuations in the halo with the density of our local region being lower than the average (around 0.3 GeV/cm^3 ). However, the accumulated neutrino signal from WIMP annihilations in the Galactic stellar disk would be insensitive to local density variations. Inside the disk, dark matter can be captured by stars causing an enhanced annihilation rate and therefore a potentially higher neutrino flux than what would be observed from elsewhere in the halo. We estimate a neutrino flux from the WIMP annihilations in the stellar disk to be enhanced by more than an order of magnitude compared to the neutrino fluxes from the halo. We offer a conservative estimate for this enhanced flux, based on the WIMP-nucleon cross-sections obtained from direct-detection experiments by assuming a density of around 0.3 GeV/cm^3 for the local DM. We also compare the detectability of these fluxes with a signal of diffuse high energy neutrinos produced in the Milky Way by the interaction of cosmic rays (CRs) with the interstellar medium (ISM). These comparative signals should be observable by large neutrino detectors.

Celebrating Polar Science

![Figure][1] CREDIT: ALAN LESHNER As we enter the fourth International Polar Year (IPY), we honor the fact that although the poles are among the most desolate places on Earth, they are also among the most scientifically rich and important to the future of the planet. The first of these “geophysical years” was 1882–1883; the most recent was 1957–1958. By now, most people know that the poles are ideal places to study the effects of global climate change. Indeed, some have called polar glaciers and ice sheets the “canaries in the mine” of climate change. Because the impacts of climate change are disproportionately felt at high latitudes, polar ecosystems will continue to bear careful watching. Cores through the polar ice shelves into the underwater sediment provide a record of Earth's biological and geological history over millions of years. The Arctic has also given us a history of human settlement and associated climate records that span thousands of years and offer an outstanding base for integrated research on global systems and human adaptation. The poles are also home to some of the most unusual species, living successfully in incredibly cold and dark water hundreds of meters under the ice. ![Figure][1] The air is so pristine that scientists at the Amundsen-Scott South Pole Station, poised atop a constantly shifting ice sheet several miles thick, give out little vials labeled “cleanest air on earth.” That air provides a matchless environment in which cosmologists and astronomers can study the origins and evolution of the universe. Their work will be accelerated by a brand-new 10-meter telescope, transported to the South Pole in sections on turboprop freight planes and assembled outside at −60°C. Work also continues on the world's largest neutrino detector, called IceCube, which after 6 years of work will occupy a cubic kilometer of ice beneath the South Pole Station. Antarctic polar ice turns out to be an ideal medium for detecting neutrinos because it is exceptionally pure, transparent, and free of radioactivity. The IPY epitomizes the globalization of science. Organized by the International Council for Science (ICSU) and the World Meteorological Organization, over 60 nations will contribute thousands of scientists to it to work together on over 200 projects. According to the organizers, “The fundamental concept of the IPY 2007–2008 is of an intensive burst of internationally coordinated, interdisciplinary, scientific research and observations focused on the Earth's polar regions.” The IPY focuses on new ways to both understand the polar regions and develop enhanced, long-lasting observational facilities and infrastructure. It also aims to recruit a new generation of polar scientists and engineers. The IPY offers the scientific community a superb opportunity to reach out to citizens around the world with the wonders of science and its applicability to crucial issues affecting them and generations to come. IPY research projects will include mathematical, physical, biological, behavioral, and social scientists and a wide range of engineering researchers. This mix of disciplines makes this polar year initiative unique, because the earlier ones were strictly geophysical. This IPY specifically includes research directed at the human elements of polar regions “to investigate the cultural, historical, and social processes that shape the sustainability of circumpolar human societies.” Its multidisciplinary character underscores how much society depends on the full array of sciences—mathematics; the physical, life, and social sciences; and engineering—to fully understand the natural world, how to preserve it, and how to make sure humans will continue to have a secure, productive, and fulfilling place in it. Reaping the benefits of this grand IPY initiative is not only up to the global scientific community. It also will depend on the wisdom of policymakers around the world to provide enough resources to ensure its success. The recent budget frenzies in the United States came dangerously close to compromising, or at least substantially delaying, this country's participation. We all need to be vigilant and make certain that the great opportunities inherent in the IPY are not forsaken. [1]: pending:yes

Neutrino Astrophysics: A New Tool for Exploring the Universe

In the past four decades a new type of astronomy has emerged, where instead of looking up into the sky, "telescopes" are buried miles underground or deep under water or ice and search not for photons (that is, light), but rather for particles called neutrinos. Neutrinos are nearly massless particles that interact very weakly with matter. The detection of neutrinos emitted by the Sun and by a nearby supernova provided direct tests of the theory of stellar evolution and led to modifications of the standard model describing the properties of elementary particles. At present, several very large neutrino detectors are being constructed, aiming at the detection of the most powerful sources of energy and particles in the universe. The hope is that the detection of neutrinos from these sources, which are extra-Galactic and are most likely powered by mass accretion onto black holes, will not only allow study of the sources, but, much like solar neutrinos, will also provide new information about fundamental properties of matter.

New Prospects for High-energy Neutrinos from gamma-ray Bursts

High-energy neutrinos from Gamma-Ray Bursts (GRBs) have been expected since the pre-Swift era. Such signals may be detected by future large neutrino detectors such as IceCube. Recently Swift has shown several novel phenomena. We suggest the new prospects for high-energy neutrino emission in the Swift era. Expected signals, if detected, are useful for revealing of the nature of GRBs.

Accelerator measurements of the Askaryan effect in rock salt: A roadmap toward teraton underground neutrino detectors

We report on further SLAC measurements of the Askaryan effect: coherent radio emission from charge asymmetry in electromagnetic cascades. We used synthetic rock salt as the dielectric medium, with cascades produced by GeV bremsstrahlung photons at the Final Focus Test Beam. We extend our prior discovery measurements to a wider range of parameter space and explore the effect in a dielectric medium of great potential interest to large scale ultra-high energy neutrino detectors: rock salt (halite), which occurs naturally in high purity formations containing in many cases hundreds of cubic km of water-equivalent mass. We observed strong coherent pulsed radio emission over a frequency band from 0.2-15 GHz. A grid of embedded dual-polarization antennas was used to confirm the high degree of linear polarization and track the change of direction of the electric-field vector with azimuth around the shower. Coherence was observed over 4 orders of magnitude of shower energy. The frequency dependence of the radiation was tested over two orders of magnitude of UHF and microwave frequencies. We have also made the first observations of coherent transition radiation from the Askaryan charge excess, and the result agrees well with theoretical predictions. Based on these results we have performed detailedmore » and conservative simulation of a realistic GZK neutrino telescope array within a salt-dome, and we find it capable of detecting 10 or more contained events per year from even the most conservative GZK neutrino models.« less

The old carbon project: how old is old?

The goal of the old carbon project is to measure the ratio of 14C to 12C in methane at levels below 10−18 by accelerator mass spectrometry (AMS). This research is chiefly motivated by the need for very low background raw materials (methane, petroleum) to manufacture scintillator fluids for large volume neutrino detectors, particularly for solar neutrinos. The 14C activity in such material, introduced by the radioactivity of the reservoir rocks, cosmic rays or later handling, limits the low-energy sensitivity of the neutrino detector. This paper reviews the scintillator requirements for low-energy neutrino observation in terms of the 14C/12C ratio, as well as earlier AMS and decay counting measurements of this ratio at the 10−18 level. Recent experiments to determine the limitations of the heavy element line on the IsoTrace spectrometer for these ratio measurements are reported; analysis of the data obtained to date indicate a maximum interference limit of 14C/12C≈10−19. This progress report will also mention some methods for reducing this interference further.