Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session C14: Low Energy Cosmic Rays |
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Sponsoring Units: DAP Chair: Eun-Suk Seo, University of Maryland Room: Key 10 |
Saturday, April 11, 2015 1:30PM - 1:42PM |
C14.00001: Measurements of Hydrogen and Helium Isotopes with the BESS-Polar II Instrument Nicolas Picot-Clemente The Balloon-Borne Experiment with a Superconducting Spectrometer (BESS-Polar II) flew successfully over Antarctica for 24.5 days in December 2007 through January 2008 during a period of minimum Solar activity. BESS-Polar II is configured with a solenoidal superconducting magnet and a suite of precision particle detectors. It can accurately identify hydrogen and helium isotopes among the incoming cosmic-ray nuclei with energies from 0.2 up to about 1.5 GeV/n. The long duration of the flight, and the good stability of the detectors increased the number of cosmic-ray events previously recorded with BESS-Polar I by a factor of 5, reaching about 4.7 billion collected particles. This allows to study and measure energy spectrum of hydrogen and helium isotope fluxes with unprecedented precision. The isotope flux and ratio measurements with BESS-Polar II will be presented and compared to previous measurements and theoretical predictions. They provide essential information to constrain cosmic-ray propagation models. [Preview Abstract] |
Saturday, April 11, 2015 1:42PM - 1:54PM |
C14.00002: Measurement by ACE-CRIS of the $^{60}$Fe/Fe ratio in Galactic Cosmic Rays W.R. Binns, M.H. Israel, K.A. Lave, E.R. Christian, G.A. de Nolfo, T.T. von Rosenvinge, A.C. Cummings, R.A. Leske, R.A. Mewaldt, E.C. Stone, M.E. Wiedenbeck We have measured the abundance of the radioactive isotope $^{60}$Fe (2.6 Myr half-life) relative to Fe in the galactic cosmic rays using the Cosmic Ray Isotope Spectrometer (CRIS) on NASA's Advanced Composition Explorer (ACE) satellite. The data correspond to 5802 days of data collection beginning December 4, 1997. The excellent resolution in mass that we obtain results in essentially complete separation of $^{60}$Fe from the much more abundant stable isotopes of Fe. For the data set selected, we detected a total of fifteen $^{60}$Fe nuclei and obtain a preliminary source abundance ratio for $^{60}$Fe/Fe of (4$\pm$1) $\times$ 10$^{-5}$. Of the fifteen $^{60}$Fe nuclei we estimate that less than 1 event could have resulted from interactions of heavier nuclei during propagation from the source, or misidentification from unrecognized interactions in the instrument. This ratio can be used to constrain the nucleosynthesis processes that contribute to the observed cosmic rays and to set an upper limit to the time between nucleosynthesis and acceleration. It will also be discussed in the light of observations of gamma-rays from decay of $^{60}$Fe ejected by supernovae. [Preview Abstract] |
Saturday, April 11, 2015 1:54PM - 2:06PM |
C14.00003: Ultra-Heavy Galactic Cosmic Ray Abundances from the SuperTIGER Instrument Ryan Murphy, W.R. Binns, R.G. Bose, P.F. Dowkontt, M.H. Israel, B.F. Rauch, J.E. Ward, T.J. Brandt, G.A. De Nolfo, T. Hams, J.T. Link, J.W. Mitchell, K. Sakai, M. Sasaki, A.W. Labrador, R.A. Mewaldt, E.C. Stone, C.J. Waddington, M.E. Wiedenbeck The SuperTIGER (Trans-Iron Galactic Element Recorder) experiment was launched on a long-duration balloon flight from Williams Field, Antarctica, on December 8, 2012. SuperTIGER flew for a total of 55 days at a mean atmospheric depth of 4.4 g/cm$^2$. The instrument measured the abundances of galactic cosmic rays in the charge (Z) range Z$=$10 to Z$=$40 with high statistical precision and excellent charge resolution, displaying well-resolved individual-element peaks at every charge up to and including Z$=$40. We will describe the instrument, data analysis techniques used, balloon flight, and payload recovery. The data that will be presented contain more than 600 events in the charge range from Z$=$30 to Z$=$40, with charge resolution at iron of \textless 0.18 cu. Our results confirm with improved statistics the earlier results from TIGER supporting a model of cosmic-ray origin in OB associations, with preferential acceleration of refractory elements over volatile elements. [Preview Abstract] |
Saturday, April 11, 2015 2:06PM - 2:18PM |
C14.00004: Study of TeV Cosmic Rays with HAWC Daniel Fiorino, Collin Buelo The High-Altitude Water Cherenkov (HAWC) Observatory is an extensive air-shower detector located at an altitude of 4100 meters in Mexico. HAWC is sensitive to cosmic rays and gamma rays at TeV energies. The cosmic-ray arrival-direction distribution at these energies shows significant anisotropy on large and small angular scales, including several regions of part-per-mille excess flux. We present studies of the anisotropy and the excess regions based on data observed with HAWC since June 2013 during the construction phase. [Preview Abstract] |
Saturday, April 11, 2015 2:18PM - 2:30PM |
C14.00005: Developing a Pass 8 Cosmic-Ray Proton Event Class David M. Green, Elizabeth A. Hays The Pass 8 improved gamma-ray simulation and reconstruction package for the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope has drastically enhanced the ability of the LAT to perform gamma-ray science. The Pass 8 improvements have also allowed for the development of a new cosmic-ray proton analysis. Using these new algorithms, we are able to create a proton event class which can be used for future studies, including spectral and anisotropy analyses. This developing event selection has a high acceptance with energies from 50 GeV to over 1 TeV and, with over 6 years of data, will give high statistics for future analyses. Currently, energy reconstruction and systematic errors in the acceptance are being investigated. A future anisotropy study is of interest because of less dependence on these factors than a spectral analysis. We present a detailed study of this new proton event class for the Pass 8 proton analysis. [Preview Abstract] |
Saturday, April 11, 2015 2:30PM - 2:42PM |
C14.00006: Improving Directional Reconstruction for IceCube's Most Interesting Events Kyle Jero The gap between IceCube's neutrino point source limits and diffuse astrophysical flux indicates a physical description of many weakly emitting sources. This picture makes the detection of an individual source via clustering methods difficult. However, by utilizing the atmospheric neutrino self veto in the southern sky and energy arguments in the southern sky, the likelihood of individual events, especially tracks, being astrophysical can be assessed. In an ensemble of these events, a calculable fraction must originate from a source making them good candidates for source list correlations and multi-messenger searches. As a result, it is worthwhile to give special attention to these event's directional reconstruction. In this talk I will discuss the most accurate and computationally intensive reconstruction algorithm utilized by IceCube and recent improvements to the utilization of the algorithm which can enhance both it's impact on future source correlation and multi-messenger searches. [Preview Abstract] |
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