Bulletin of the American Physical Society
Fall 2009 Meeting of the Four Corners Section of the APS
Volume 54, Number 14
Friday–Saturday, October 23–24, 2009; Golden, Colorado
Session H1: Astroparticle Symposium IV: UHE Cosmic Rays -- Anistropy Studies |
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Chair: Miguel Mostafa, Colorado State University Room: Green Center 211 |
Saturday, October 24, 2009 11:20AM - 11:32AM |
H1.00001: Intrinsic anisotropy of the UHECR from the Pierre Auger Observatory Kasey Ackerman Using a differential two-point correlation method, we examine the distribution of arrival directions of the highest energy cosmic rays detected with the Pierre Auger Observatory. We compare this distribution against a hypothesis of isotropy. The number of pairs of events at a small angular scale is consistent with an isotropic distribution only 3 percent of the time. We also study the number of pairs at a small angular scale as a function of the energy of the cosmic rays. Data show an anisotropic distribution only at energies above 57 EeV. [Preview Abstract] |
Saturday, October 24, 2009 11:32AM - 11:44AM |
H1.00002: Two Point Autocorrelation Analysis of Auger Highest Energy Events Backtracked in Galactic Magnetic Field Yevgeniy Petrov Searches for sources of the highest-energy cosmic rays traditionally have included looking for clusters of event arrival directions on the sky. The smallest cluster is a pair of events falling within some angular window.~ In contrast to the standard two point (2-pt) autocorrelation analysis, this work takes into account influence of the galactic magnetic field (GMF). The highest energy events, those above 50EeV, collected by the surface detector of the Pierre Auger Observatory between January 1, 2004 and May 31, 2009 are used in the analysis. Having assumed protons as primaries, events are backtracked through BSS{\_}S, BSS{\_}A, ASS{\_}S and ASS{\_}A versions of Harari-Mollerach-Roulet (HMR) model of the GMF. For each version of the model, a 2-pt autocorrelation analysis is applied to the backtracked events and to 10$^{5}$ isotropic Monte Carlo realizations weighted by the Auger exposure. Scans in energy, separation angular window and different model parameters reveal clustering at different angular scales. Small angle clustering at 2-3 deg is particularly interesting and it is compared between different field scenarios. The strength of the autocorrelation signal at those angular scales differs between BSS and ASS versions of the HMR model. The BSS versions of the model tend to defocus protons as they arrive to Earth whereas for the ASS, in contrary, it is more likely to focus them. [Preview Abstract] |
Saturday, October 24, 2009 11:44AM - 11:56AM |
H1.00003: Search for Large-Scale Anisotropy of Ultrahigh Energy Cosmic Rays with HiRes Stereo Data Gordon Thomson, Peter Tinyakov, Hylke Koers We report on a search for correlations between local large-scale structure and arrival directions of ultrahigh energy cosmic rays, detected by the High Resolution Fly's Eye (HiRes) experiment operating in stereoscopic mode. HiRes has observed cosmic rays with energies up to just over 100 EeV. The highest energy events have a relatively nearby horizon, and one expects that they should point back to their sources to a few-degree accuracy, or at least toward local large-scale structure. HiRes currently has the largest exposure of any experiment in the northern hemisphere. The experiment and search methods will be described and results will be presented. [Preview Abstract] |
Saturday, October 24, 2009 11:56AM - 12:08PM |
H1.00004: Predictions of the small scale clustering properties of ultra-high energy cosmic rays Patrick Younk I present theoretical estimates of the small scale clustering properties of ultra-high energy cosmic rays (UHECR) assuming that: (1) the UHECR sources are extragalactic, and (2) the Greisen-Zatsepin-Kuz'min effect is operational. I show that assumptions on the particle charge and intervening magnetic fields have a large effect on the predicted small scale clustering. Therefore, a measurement of the small scale clustering can be used to constrain the parameter space that describes the allowed distribution of particle charge and the allowed structure of the intervening magnetic fields. I show how such constraints can be determined in the near future. [Preview Abstract] |
Saturday, October 24, 2009 12:08PM - 12:20PM |
H1.00005: Search for coincidences with gamma-ray bursts in Pierre Auger Observatory data David Thomas We analyze extensive air shower data collected by the Pierre Auger Observatory to search for coincidences between the arrival directions of ultra-high energy cosmic rays and the positions of gamma-ray bursts. We also analyze the trigger rate data from individual surface detector stations to search for an increase of the average trigger rate over the entire surface detector array in correlation with gamma-ray bursts. [Preview Abstract] |
Saturday, October 24, 2009 12:20PM - 12:32PM |
H1.00006: Analysis Techniques used for Telescope Array Surface Detector Data Dmitri Ivanov, Benjamin Stokes, Gordon Thomson The Telescope Array experiment is the largest cosmic ray experiment in the northern hemisphere. It consists of a surface detector (SD) of 507 scintillation counters and three fluorescence stations overlooking the SD. We are analyzing the SD data using a new technique, which consists of generating a Monte Carlo (MC) simulation of the SD that has all the characteristics of the actual data, comparing the MC with the data to verify the accuracy of the MC, and calculation of the SD aperture from the MC information. Our analysis based solely upon the data, our method of generating CORSIKA showers without the problems caused by thinning, and comparisons of MC with data will be shown. [Preview Abstract] |
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