Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session P13: UHECR Detection and Results |
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Sponsoring Units: DAP Chair: Jordan Goodman, University of Maryland Room: Washington 6 |
Monday, February 15, 2010 10:45AM - 10:57AM |
P13.00001: Observations vs. Simulations of Golden Hybrid Events at the Pierre Auger Observatory Jeff Allen The hybrid detection method employed by the Pierre Auger Observatory, detecting the longitudinal development with the Florescence Detector (FD) and the ground particle signal with the Surface Detector (SD), places strong constraints on individual detected air showers. We utilize events well measured by both methods, Golden Hybrid events, to create simulated air showers which attempt to simultaneously match the signal seen in the FD and SD on an event-by-event basis. The comparison of the simulated and measured events provides a direct test for air shower simulations and the high energy hadronic event generators upon which they depend. The nature of the discrepancies seen in this comparison can provide guidance as to the primary cosmic ray composition, overall energy calibration, and hadronic interactions beyond the reach of accelerator experiments. [Preview Abstract] |
Monday, February 15, 2010 10:57AM - 11:09AM |
P13.00002: Measurement of the longitudinal profile of extensive air showers with the Pierre Auger Observatory Florin Ionita The Pierre Auger Observatory is a cosmic ray detector designed to measure the flux, the energy spectrum, and the mass composition of ultra-high energy cosmic rays. In this talk, we describe the measurement of $X_{\rm max}$, the slant depth at which extensive air showers induced by cosmic rays reach maximum development. The evolution with energy of the average value of $X_{\rm max}$ and its fluctuations are two observables sensitive to the mass composition of cosmic rays. We present the latest measurements of these quantities and discuss briefly their interpretation in terms of the cosmic ray mass composition. [Preview Abstract] |
Monday, February 15, 2010 11:09AM - 11:21AM |
P13.00003: Measurement of the Flux of Ultra-High Energy Cosmic Rays at the Pierre Auger Observatory Segev BenZvi The energy spectrum of cosmic rays above $10^{18}$ eV has been measured with unprecedented statistics at the Pierre Auger Observatory. From air shower measurements made using the fluorescence telescopes and the surface detector array at the Auger site, we report three measurements of the energy spectrum: using downgoing events observed with the surface array only; using nearly horizontal showers observed with the surface array; and using showers observed with the fluorescence telescopes and surface array in combination. These three techniques use partly independent data sets with different systematic uncertainties, providing useful checks of the spectrum measurement. The observed spectra agree within systematic uncertainties, and indicate a hardening of the spectral index near $10^{18.6}$ eV and a significant suppression of the flux above $10^{19.5}$ eV. We will describe the systematic uncertainties of the reported fluxes, and discuss the astrophysical implications of these measurements. [Preview Abstract] |
Monday, February 15, 2010 11:21AM - 11:33AM |
P13.00004: Ultra-high energy photon studies with the Pierre Auger Observatory Viviana Scherini While the most likely candidates for cosmic rays above $10^{18}$~eV are protons and nuclei, many of the scenarios of cosmic ray origin also predict a photon component. Detection of this component is of importance for cosmic ray physics but also opens a new research window with impact on astrophysics, cosmology, particle and possibly fundamental physics. The Pierre Auger Observatory has been used for photon searches of unprecedented sensitivity. The current status of this search will be reported, including experimental limits at EeV energies. [Preview Abstract] |
Monday, February 15, 2010 11:33AM - 11:45AM |
P13.00005: Hybrid Observation with the Telecsope Array Observatory Benjamin Stokes, Dmitri Ivanov, Gordon Thomson The Telescope Array (TA) is the largest ultra-high energy cosmic ray (UHECR) observatory in the Northern Hemisphere. TA observes cosmic rays with two principal components: Optical detectors use nitrogen fluorescence to observe the longitudinal development of cosmic ray extensive air showers (EAS) in the atmosphere while an array of scintillator counters captures the lateral cross sections of EAS at ground-level. While both methods of observation independently yield important information about the energy, composition, and arrival directions of UHECR, far better data resolution can be achieved by utilizing hybrid observation. We will present the results of a simulation study of TA hybrid efficiency and data resolution. [Preview Abstract] |
Monday, February 15, 2010 11:45AM - 11:57AM |
P13.00006: Measurement of the Flux of Ultrahigh Energy Cosmic Rays by the Surface Detector of the Telescope Array Experiment Gordon Thomson, Dmitri Ivanov, Benjamin Stokes We have measured the flux of ultrahigh energy cosmic rays using the surface detector of the Telescope Array experiment. We developed an analysis technique based solely on the data, using parameterizations similar to those used in the AGASA experiment. We calculated the aperture of the detector by making a detailed Monte Carlo simulation of the experiment, and tested it by comparing distributions of kinematical and dynamical quantities with the data. The methods will be described and the results presented. [Preview Abstract] |
Monday, February 15, 2010 11:57AM - 12:09PM |
P13.00007: Measurement of the UHECR Flux by the Telescope Array Fluorescence Detectors Sean Stratton, Lauren Scott The Telescope Array (TA), the first dedicated Northern Hemisphere ``hybrid'' ultrahigh energy cosmic ray (UHECR) detector, is online in Millard Country, Utah. The three Fluorescence Detector sites (FD) located at Black Rock Mesa, Long Ridge and Middle Drum have been taking data since November 2007. By measuring the characteristics of UHECR-induced extensive air showers using the FD, we can measure the energies, composition and arrival directions of the highest- energy cosmic rays. We will show data from the experiment, comparisons with simulated data from our full detector Monte Carlo simulation program, and our measurement of the UHECR energy spectrum. [Preview Abstract] |
Monday, February 15, 2010 12:09PM - 12:21PM |
P13.00008: Multi-spectra Cosmic Ray Flux Measurement Xiaochun He, Mathes Dayananda The Earth's upper atmosphere is constantly bombarded by rain of charged particles known as primary cosmic rays. These primary cosmic rays will collide with the atmospheric molecules and create extensive secondary particles which shower downward to the surface of the Earth. In recent years, a few studies have been done regarding to the applications of the cosmic ray measurements and the correlations between the Earth's climate conditions and the cosmic ray fluxes [1,2,3]. Most of the particles, which reach to the surface of the Earth, are muons together with a small percentage of electrons, gammas, neutrons, etc. At Georgia State University, multiple cosmic ray particle detectors have been constructed to measure the fluxes and energy distributions of the secondary cosmic ray particles. In this presentation, we will briefly describe these prototype detectors and show the preliminary test results. Reference: [1] K.Borozdin, G.Hogan, C.Morris, W.Priedhorsky, A.Saunders, L.Shultz, M.Teasdale, Nature, Vol.422, 277 (2003). [2] L.V. Egorova, V. Ya Vovk, O.A. Troshichev, Journal of Atmospheric and Terrestrial Physics 62, 955-966 (2000). [3] Henrik Svensmark, Phy. Rev. Lett. 81, 5027 (1998). [Preview Abstract] |
Monday, February 15, 2010 12:21PM - 12:33PM |
P13.00009: A Primary Energy Reconstruction Method for Air Shower Array Experiments Samvel ter-Antonyan, Ali Fazely A multi-parameter event-by-event primary energy reconstruction method is presented for the air shower array experiments such as IceTop. Results are obtained using CORSIKA EAS simulations taking into account the detector response and shower reconstruction uncertainties. Energy reconstruction for the primary nuclei within $10-12\%$ in the energy region of $E>10 PeV$ are achievable, regardless of nucleus type. [Preview Abstract] |
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