89 research outputs found

    Search for Anisotropy of Ultra-High Energy Cosmic Rays with the Telescope Array Experiment

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    We study the anisotropy of Ultra-High Energy Cosmic Ray (UHECR) events collected by the Telescope Array (TA) detector in the first 40 months of operation. Following earlier studies, we examine event sets with energy thresholds of 10 EeV, 40 EeV, and 57 EeV. We find that the distributions of the events in right ascension and declination are compatible with an isotropic distribution in all three sets. We then compare with previously reported clustering of the UHECR events at small angular scales. No significant clustering is found in the TA data. We then check the events with E>57 EeV for correlations with nearby active galactic nuclei. No significant correlation is found. Finally, we examine all three sets for correlations with the large-scale structure of the Universe. We find that the two higher-energy sets are compatible with both an isotropic distribution and the hypothesis that UHECR sources follow the matter distribution of the Universe (the LSS hypothesis), while the event set with E>10 EeV is compatible with isotropy and is not compatible with the LSS hypothesis at 95% CL unless large deflection angles are also assumed. We show that accounting for UHECR deflections in a realistic model of the Galactic magnetic field can make this set compatible with the LSS hypothesis.Comment: 10 pages, 9 figure

    Upper limit on the flux of photons with energies above 10(19) eV using the Telescope Array surface detector

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    We search for ultra-high energy photons by analyzing geometrical properties of shower fronts of events registered by the Telescope Array surface detector. By making use of an event-by-event statistical method, we derive upper limits on the absolute flux of primary photons with energies above 1019, 1019.5, and 1020 eV based on the first three years of data takenopen4

    CORRELATIONS OF THE ARRIVAL DIRECTIONS OF ULTRA-HIGH ENERGY COSMIC RAYS WITH EXTRAGALACTIC OBJECTS AS OBSERVED BY THE TELESCOPE ARRAY EXPERIMENT

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    We search for correlations between the positions of extragalactic objects and the arrival directions of ultra-high energy cosmic rays (UHECRs) with primary energy E ??? 40 EeV as observed by the surface detector array of the Telescope Array (TA) experiment during the first 40 months of operation. We examine several public astronomical object catalogs, including the Veron-Cetty and Veron catalog of active galactic nuclei. We count the number of TA events correlated with objects in each catalog as a function of three parameters: the maximum angular separation between a TA event and an object, the minimum energy of the events, and the maximum redshift of the objects. We determine the combination of these parameters that maximizes the correlations, and we calculate the probability of having the same levels of correlations from an isotropic distribution of UHECR arrival directions. No statistically significant correlations are found when penalties for scanning over the above parameters and for searching in several catalogs are taken into account.open4

    The Cosmic Ray Energy Spectrum Observed with the Surface Detector of the Telescope Array Experiment

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    The Telescope Array (TA) collaboration has measured the energy spectrum of ultra-high energy cosmic rays with primary energies above 1.6 x 10^(18) eV. This measurement is based upon four years of observation by the surface detector component of TA. The spectrum shows a dip at an energy of 4.6 x 10^(18) eV and a steepening at 5.4 x 10^(19) eV which is consistent with the expectation from the GZK cutoff. We present the results of a technique, new to the analysis of ultra-high energy cosmic ray surface detector data, that involves generating a complete simulation of ultra-high energy cosmic rays striking the TA surface detector. The procedure starts with shower simulations using the CORSIKA Monte Carlo program where we have solved the problems caused by use of the "thinning" approximation. This simulation method allows us to make an accurate calculation of the acceptance of the detector for the energies concerned.Comment: Accepted for publication by Astrophysical Journal Letter

    The surface detector array of the Telescope Array experiment

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    The Telescope Array (TA) experiment, located in the western desert of Utah,USA, is designed for observation of extensive air showers from extremely high energy cosmic rays. The experiment has a surface detector array surrounded by three fluorescence detectors to enable simultaneous detection of shower particles at ground level and fluorescence photons along the shower track. The TA surface detectors and fluorescence detectors started full hybrid observation in March, 2008. In this article we describe the design and technical features of the TA surface detector.Comment: 32 pages, 17 figure

    New air fluorescence detectors employed in the Telescope Array experiment

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    Since 2007, the Telescope Array (TA) experiment, based in Utah, USA, has been observing ultra high energy cosmic rays to understand their origins. The experiment involves a surface detector (SD) array and three fluorescence detector (FD) stations. FD stations, installed surrounding the SD array, measure the air fluorescence light emitted from extensive air showers (EASs) for precise determination of their energies and species. The detectors employed at one of the three FD stations were relocated from the High Resolution Fly's Eye experiment. At the other two stations, newly designed detectors were constructed for the TA experiment. An FD consists of a primary mirror and a camera equipped with photomultiplier tubes. To obtain the EAS parameters with high accuracies, understanding the FD optical characteristics is important. In this paper, we report the characteristics and installation of new FDs and the performances of the FD components. The results of the monitored mirror reflectance during the observation time are also described in this report.Comment: 44 pages, 23 figures, submitted to NIM-

    Definitions, pathophysiology, and epidemiology of acute cholangitis and cholecystitis: Tokyo Guidelines

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    This article discusses the definitions, pathophysiology, and epidemiology of acute cholangitis and cholecystitis. Acute cholangitis and cholecystitis mostly originate from stones in the bile ducts and gallbladder. Acute cholecystitis also has other causes, such as ischemia; chemicals that enter biliary secretions; motility disorders associated with drugs; infections with microorganisms, protozoa, and parasites; collagen disease; and allergic reactions. Acute acalculous cholecystitis is associated with a recent operation, trauma, burns, multisystem organ failure, and parenteral nutrition. Factors associated with the onset of cholelithiasis include obesity, age, and drugs such as oral contraceptives. The reported mortality of less than 10% for acute cholecystitis gives an impression that it is not a fatal disease, except for the elderly and/or patients with acalculous disease. However, there are reports of high mortality for cholangitis, although the mortality differs greatly depending on the year of the report and the severity of the disease. Even reports published in and after the 1980s indicate high mortality, ranging from 10% to 30% in the patients, with multiorgan failure as a major cause of death. Because many of the reports on acute cholecystitis and cholangitis use different standards, comparisons are difficult. Variations in treatment and risk factors influencing the mortality rates indicate the necessity for standardized diagnostic, treatment, and severity assessment criteria
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