111 research outputs found
High Energy Cosmic Neutrinos
While the general principles of high-energy neutrino detection have been
understood for many years, the deep, remote geographical locations of suitable
detector sites have challenged the ingenuity of experimentalists, who have
confronted unusual deployment, calibration, and robustness issues. Two high
energy neutrino programs are now operating (Baikal and AMANDA), with the
expectation of ushering in an era of multi-messenger astronomy, and two
Mediterranean programs have made impressive progress. The detectors are
optimized to detect neutrinos with energies of the order of 1-10 TeV, although
they are capable of detecting neutrinos with energies of tens of MeV to greater
than PeV. This paper outlines the interdisciplinary scientific agenda, which
span the fields of astronomy, particle physics, and cosmic ray physics, and
describes ongoing worldwide experimental programs to realize these goals.Comment: 15 pages, 9 figures, talk presented at the Nobel Symposium on
Particle Physics and the Universe, Sweden, August 199
Ross Ice Shelf in situ radio-frequency ice attenuation
We have measured the in situ average electric field attenuation length for
radio-frequency signals broadcast vertically through the Ross Ice Shelf. We
chose a location, Moore Embayment, south of Minna Bluff, known for its high
reflectivity at the ice-sea interface. We confirmed specular reflection and
used the return pulses to measure the average attenuation length from 75-1250
MHz over the round-trip distance of 1155 m. We find the average electric field
attenuation length to vary from 500 m at 75 MHz to 300 m at 1250 MHz, with an
experimental uncertainty of 55 to 15 m. We discuss the implications for
neutrino telescopes that use the radio technique and include the Ross Ice Shelf
as part of their sensitive volume.Comment: 6 pages, 7 figures, Fig. 7 updated and minor text changes made since
the published versio
Constraints on Extragalactic Point Source Flux from Diffuse Neutrino Limits
We constrain the maximum flux from extragalactic neutrino point sources by
using diffuse neutrino flux limits. We show that the maximum flux from
extragalactic point sources is E^2(dN/dE) < 1.4 x 10^-9 (L_nu/2x10^43
erg/s)^1/3 GeV cm-^2 s^-1 from individual point sources with average neutrino
luminosity per decade, L_nu. It depends only slightly on factors such as the
inhomogeneous matter density distribution in the local universe, the luminosity
distribution, and the assumed spectral index. The derived constraints are at
least one order of magnitude below the current experimental limits from direct
searches. Significant constraints are also derived on the number density of
neutrino sources and on the total neutrino power density.Comment: 7 pages, 3 figures, and 2 table
Overview of the ANITA project
Journal ArticleThe ANITA project is designed to investigate ultra-high energy (>1017 eV) cosmic ray interactions throughout the universe by detecting the neutrinos created in those interactions. These high energy neutrinos are detectable through their interactions within the Antarctic ice sheet, which ANITA will use as a detector target that effectively converts the neutrino interactions to radio pulses. This paper will give an overview of the project including scientific objectives, detection description and mission design
Report of the Fieldwork Data Sustainability Project (FIDAS)
Fieldworkers typically collect data in a rather ad-hoc way during fieldwork, often leading to patchy and highly variable metadata quality at the time of submission to a digital repository. It can be very difficult or even impossible to reconstruct some of this information at a later date, yet these resources are often unique and unrepeatable records of highly significant events collected at considerable expense of researcher time, effort and resources. From the repository perspective, lack of metadata (including preservation metadata) can have serious implications not only for ingestion into a repository, but also for subsequent archival management and dissemination of archival information. This project aimed to extend the scope of the OAIS model to facilitate sustainable data collection and description of digital objects from the time of creation during fieldwork, and to integrate this workflow with repository ingestion, management, and dissemination requirements
Cosmic-Ray Positrons: Are There Primary Sources?
Cosmic rays at the Earth include a secondary component originating in
collisions of primary particles with the diffuse interstellar gas. The
secondary cosmic rays are relatively rare but carry important information on
the Galactic propagation of the primary particles. The secondary component
includes a small fraction of antimatter particles, positrons and antiprotons.
In addition, positrons and antiprotons may also come from unusual sources and
possibly provide insight into new physics. For instance, the annihilation of
heavy supersymmetric dark matter particles within the Galactic halo could lead
to positrons or antiprotons with distinctive energy signatures. With the
High-Energy Antimatter Telescope (HEAT) balloon-borne instrument, we have
measured the abundances of positrons and electrons at energies between 1 and 50
GeV. The data suggest that indeed a small additional antimatter component may
be present that cannot be explained by a purely secondary production mechanism.
Here we describe the signature of the effect and discuss its possible origin.Comment: 15 pages, Latex, epsfig and aasms4 macros required, to appear in
Astroparticle Physics (1999
Radar absorption, basal reflection, thickness and polarization measurements from the Ross Ice Shelf, Antarctica
Radio-glaciological parameters from the Moore’s Bay region of the Ross Ice Shelf, Antarctica, have been measured. The thickness of the ice shelf in Moore’s Bay was measured from reflection times of radio-frequency pulses propagating vertically through the shelf and reflecting from the ocean, and is found to be 576 ± 8 m. Introducing a baseline of 543 ± 7m between radio transmitter and receiver allowed the computation of the basal reflection coefficient, R, separately from englacial loss. The depth-averaged attenuation length of the ice column, 〈L〉 is shown to depend linearly on frequency. The best fit (95% confidence level) is 〈L(ν)〉= (460±20) − (180±40)ν m (20 dB km−1), for the frequencies ν = [0.100–0.850] GHz, assuming no reflection loss. The mean electric-field reflection coefficient is (1.7 dB reflection loss) across [0.100–0.850] GHz, and is used to correct the attenuation length. Finally, the reflected power rotated into the orthogonal antenna polarization i
Visual Analytics for Epidemiologists: Understanding the Interactions Between Age, Time, and Disease with Multi-Panel Graphs
Visual analytics, a technique aiding data analysis and decision making, is a novel tool that allows for a better understanding of the context of complex systems. Public health professionals can greatly benefit from this technique since context is integral in disease monitoring and biosurveillance. We propose a graphical tool that can reveal the distribution of an outcome by time and age simultaneously.We introduce and demonstrate multi-panel (MP) graphs applied in four different settings: U.S. national influenza-associated and salmonellosis-associated hospitalizations among the older adult population (≥65 years old), 1991-2004; confirmed salmonellosis cases reported to the Massachusetts Department of Public Health for the general population, 2004-2005; and asthma-associated hospital visits for children aged 0-18 at Milwaukee Children's Hospital of Wisconsin, 1997-2006. We illustrate trends and anomalies that otherwise would be obscured by traditional visualization techniques such as case pyramids and time-series plots.MP graphs can weave together two vital dynamics--temporality and demographics--that play important roles in the distribution and spread of diseases, making these graphs a powerful tool for public health and disease biosurveillance efforts
- …