Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session R8: Ultra-High Energy Cosmic Rays I |
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Sponsoring Units: DAP Chair: Lawrence Wiencke, Colorado School of Mines Room: Governor's Square 10 |
Monday, April 15, 2013 1:30PM - 1:42PM |
R8.00001: The Galactic magnetic deflection of Cosmic Rays from Cen A Azadeh Keivani, Glennys Farrar We present the results of propagating ultra-high energy cosmic rays (UHECRs) from Centaurus A, to characterize their arrival-direction locus and determine whether Cen A can be a significant source of the UHECR excess reported by the Pierre Auger Observatory within 18 degrees of Cen A. We use the recent galactic magnetic field model of Jansson and Farrar (JF12), a 35-parameter model which includes coherent, striated and random components and is constrained by WMAP synchrotron maps and all available extragalactic rotation measures. We also present a new method to increase the efficiency of forward-tracking the UHECRs through the galactic magnetic field. Simulations are done for rigidities E/Z = 64 EV down to 1 EV, thus covering the possibility of compositions as heavy as Fe for the published UHECR events. [Preview Abstract] |
Monday, April 15, 2013 1:42PM - 1:54PM |
R8.00002: Ultra-high energy cosmic-rays: A fresh look at an old problem Patrick Younk The nature of the ultra-high energy cosmic-rays (UHECR) is an old problem with many important issues still unresolved. The body of experimental evidence has increased significantly in recent years. Much of this new knowledge has come from the Pierre Auger Observatory and the Telescope Array Project, both are cosmic-ray observatories, but there are also interesting clues from gamma-ray and neutrino observatories. In this talk I will briefly outline the current experimental evidence. Then I will discuss several distinctly different pictures with regard to the nature of the UHECR. I will argue that there is no simple picture of the UHECR that is without difficulty. I will describe some possible ways forward on both the experimental and phenomenological fronts. [Preview Abstract] |
Monday, April 15, 2013 1:54PM - 2:06PM |
R8.00003: A Search for EeV Neutron Point Sources Shih-Ho Cheng We present the results of a thorough search for EeV neutron fluxes with the surface array of the Pierre Auger Observatory. A Li-Ma significance test is applied to targets systematically placed throughout the exposed sky between -90$^\circ$ and +15$^\circ$ in declination and for four energy ranges: 1--2 EeV, 2--3 EeV, greater than 3 EeV, and greater than 1 EeV. Since no significant flux excess indicative of a discrete point source is found, an upper limit on the neutron flux is presented for each search direction. The obtained upper limits constrain the scenarios for sources of ultra-high-energy cosmic rays in the Galaxy. [Preview Abstract] |
Monday, April 15, 2013 2:06PM - 2:18PM |
R8.00004: Search for neutron sources in the energy range from 0.3 to 3 EeV with the Pierre Auger Observatory Francisco Salesa Greus, Miguel Mostafa The Pierre Auger Observatory is a cosmic ray detector located in Argentina in the Mendoza province. It consists of an array of 1600 surface detector (SD) stations equally distributed over an area of 3000~km$^{2}$. The separation between stations is 1500~m. The main goal of the observatory is to discover and understand the origin of the high-energy cosmic rays with energies exceeding 10~EeV. The granularity of a section of 27~km$^{2}$ of the SD array was increased by deploying additional tanks, with a 750~m separation. This enhancement allows the detection of cosmic rays of energies starting at 0.3~EeV. Assuming that gamma rays detected at TeV energy are produced by $\pi^{0}$ decays in sources a few kpc away with an energy spectrum that extends unbroken up to EeV energies, neutrons from these sources should be detected with the Auger Infill array. An all-sky survey, looking for Galactic neutron sources in the 0.3-3 EeV energy range will be presented in this talk. As no neutron sources were detected in the data from the Auger Infill array, the corresponding energy flux limits were computed. These limits are already of physical interest since they are of the same order of magnitude as the theoretical predictions for Galactic flux emission. [Preview Abstract] |
Monday, April 15, 2013 2:18PM - 2:30PM |
R8.00005: Measurement of the speed of Ultra-High Energy Cosmic-Ray Extensive Air Showers with the Pierre Auger Observatory Eric Mayotte At the Pierre Auger Observatory, the reconstruction of Extensive Air Showers (EAS) induced by Ultra-High Energy Cosmic-Rays (UHECR) relies on the very reasonable assumption that all EASs develop at the speed of light. However, because potential exotic species could in principle induce detectable, subluminal EASs, this assumption would lead to poor reconstructions in these rare cases. Additionally, the results of a speed-dependent reconstruction can be useful in monitoring the operation of the array, for instance if a systematic shift from the speed of light in normal showers was observed. In this context, the code for reconstructing optically detected events was modified to find the shower velocity along with the other EAS parameters. This method was first benchmarked with lasers shots fired into the sky from laser facilities located within the array. It was then employed in the multiple levels of shower reconstruction (Monocular, Stereo and Hybrid). Preliminary results from these analyses and an exotic candidate search will be presented. [Preview Abstract] |
Monday, April 15, 2013 2:30PM - 2:42PM |
R8.00006: Energy Spectrum and Composition of Ultra High Energy Cosmic Ray Showers Using Hybrid Analysis from Telescope Array Charles Jui, Monica Allen, Tareq Abu-Zayyad, Benjamin Stokes, Dmitri Ivanov The Telescope Array (TA) consists of 38 fluorescence telescopes spread over three detector sites. The three sites at located the periphery of a surface array of 507 scintillation counters, covering 700 square km, with a spacing of 1.2 km. TA is designed to study the energy spectrum, composition, and arrival direction anisotropy of ultrahigh energy cosmic rays (UHECR). A unique feature of TA is that one of three fluorescence detector (FD) sites, Middle Drum (MD), is instrumented with 14 refurbished telescopes from the High Resolution Fly's Eye (HiRes) experiment. This commonality provides TA with a direct link back to the HiRes experiment and data. Using the scintillator detector data in conjunction with the MD data improves the geometrical reconstruction and hence provides a more accurate reconstruction of the energy of the primary particle and shower profile. The Middle Drum hybrid spectrum composition results will be presented. [Preview Abstract] |
Monday, April 15, 2013 2:42PM - 2:54PM |
R8.00007: Measurement of the Ultra-High Energy Cosmic Ray Spectrum by the Telescope Array Surface Detector Benjamin Stokes The Telescope Array experiment is the largest cosmic ray observatory in the northern hemisphere. Telescope Array consists of an array of 507 scintillation counter surface detectors (TASD) augmented by three optical fluorescence telescope observatories. In analyzing the data collected by the TASD, a novel technique is employed which consists of generating a very detailed simulation that can be directly compared against actual observations. This enables a very careful analysis with a thoroughgoing understanding of the resolution constraints in the data. This method will be described and the most recent TASD measurement of the cosmic ray energy spectrum will be presented. [Preview Abstract] |
Monday, April 15, 2013 2:54PM - 3:06PM |
R8.00008: Measurement of the UHECR Energy Spectrum by the Telescope Array Fluorescence Detectors Thomas Stroman, Douglas Bergman Ultra-high-energy cosmic rays (UHECRs), subatomic charged particles of extraterrestrial origin and with kinetic energies near or exceeding $10^{18}$~eV, are very rare. The Telescope Array (TA) experiment in western Utah is the northern hemisphere's largest UHECR detector, and consists of three atmospheric fluorescence detectors (FDs) and a ground array of 507 scintillator detectors. In stand-alone ``monocular'' operation, the FDs can observe the widest range in primary UHECR energies. One FD employs refurbished hardware from the High-Resolution Fly's Eye experiment; the remaining two FDs were designed for TA and employ new hardware and analysis. We will present the UHECR energy spectrum measured by the FDs in monocular mode using data collected during the first four years of operation. [Preview Abstract] |
Monday, April 15, 2013 3:06PM - 3:18PM |
R8.00009: Anisotropy Results Using the Telescope Array Surface Detector Data Dmitri Ivanov We report on the search for anisotropy of the ultra-high energy cosmic rays using the Telescope Array surface detector data collected in the first 4 years of operation. This presentation consists of two parts. First, we search for the small scale anisotropies at the highest energies using 3 energy threshold values, E\textgreater 10 EeV, E\textgreater 40 EeV, and E\textgreater 57 EeV, where we examine the event autocorrelation function and correlations with the large scale structures. Second, we look for the intermediate and large scale anisotropies around 1 EeV. We present a significance map of cosmic ray arrival directions, a full-sky harmonic analysis in right ascension, and compare the results with the High Resolution Fly's Eye and Akeno Giant Air Shower Array experiments. [Preview Abstract] |
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