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 11 - 20 / 311234 11.The cosmic ray energy spectrum measured using the Pierre Auger ObservatoryMarko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, Francesco Fenu, 2017, published scientific conference contributionFound in: ključnih besedahKeywords: cosmic ray, energy spectrum, Pierre Auger ObservatoryPublished: 16.02.2018; Views: 1859; Downloads: 114 Fulltext (566,33 KB) 12.Report of the Telescope Array - Pierre Auger Observatory Working Group on Energy SpectrumMarko Zavrtanik, Danilo Zavrtanik, Lili Yang, Marta Trini, Serguei Vorobiov, Darko Veberič, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, Dmitri Ivanov, 2017, published scientific conference contributionFound in: ključnih besedahKeywords: Telescope Array, Pierre Auger Observatory, Energy SpectrumPublished: 19.02.2018; Views: 2256; Downloads: 143 Fulltext (398,98 KB) 13.Evidence for Declination Dependence of Ultrahigh Energy Cosmic Ray Spectrum in the Northern HemisphereJ. P. Lundquist, R.U. Abbasi, 2018, other component partsAbstract: The energy of the ultrahigh energy spectral cutoff was measured, integrating over the northern hemisphere sky, by the Telescope Array (TA) collaboration, to be 10^19.78±0.06 eV, in agreement with the High Resolution Fly's Eye (HiRes) experiment, whereas the Pierre Auger experiment, integrating over the southern hemisphere sky, measured the cutoff to be at 10^19.62±0.02 eV. An 11% energy scale difference between the TA and Auger does not account for this difference. However, in comparing the spectra of the Telescope Array and Pierre Auger experiments in the band of declination common to both experiments ( −15.7∘<δ<24.8∘ ) we have found agreement in the energy of the spectral cutoff. While the Auger result is essentially unchanged, the TA cutoff energy has changed to 10^19.59±0.06 eV. In this paper we argue that this is an astrophysical effect.Found in: ključnih besedahKeywords: Astrophysics, High Energy Astrophysical Phenomena, UHECR, Cosmic Rays, Anisotropy, Energy SpectrumPublished: 27.04.2020; Views: 1645; Downloads: 55 Fulltext (687,87 KB) 14.Search for Anisotropy in the Ultra High Energy Cosmic Ray Spectrum using the Telescope Array Surface DetectorJ. P. Lundquist, R.U. Abbasi, 2017, other component partsAbstract: The Telescope Array (TA) experiment is located in the western desert of Utah, USA, and observes ultra high energy cosmic rays (UHECRs) in the Northern hemisphere. At the highest energies, E>10~EeV, the shape of cosmic ray energy spectrum may carry an imprint of the source density distribution along the line of sight different in different directions of the sky. In this study, we search for such directional variations in the shape of the energy spectrum using events observed with the Telescope Array's surface detector. We divide the TA field of view into two nearly equal-exposure regions: the "on-source" region which we define as ±30∘ of the supergalactic plane containing mostly nearby structures, and the complementary "off-source" region where the sources are further away on average. We compare the UHECR spectra in these regions by fitting them to the broken power law and comparing the resulting parameters. We find that the off-source spectrum has an earlier break at highest energies. The chance probability to obtain such or larger difference in statistically equivalent distributions is estimated as 6.2±1.1×10−4 (3.2σ) by a Monte-Carlo simulation. The observed difference in spectra is in a reasonable quantitative agreement with a simplified model that assumes that the UHECR sources trace the galaxy distribution from the 2MRS catalogue, primary particles are protons and the magnetic deflections can be neglected.Found in: ključnih besedahKeywords: cosmic radiation: UHE, detector: surface, cosmic radiation: spectrum, cosmic radiation: energy spectrum, deflection: magnetic, numerical calculations: Monte Carlo, anisotropyPublished: 27.04.2020; Views: 1524; Downloads: 54 Fulltext (169,05 KB) 15.The energy spectrum of cosmic rays above 1017.2 eV measured by the fluorescence detectors of the Telescope Array experiment in seven yearsJ. P. Lundquist, R.U. Abbasi, 2016, original scientific articleAbstract: The Telescope Array (TA) experiment is the largest detector to observe ultra-high-energy cosmic rays in the northern hemisphere. The fluorescence detectors at two stations of TA are newly constructed and have now completed seven years of steady operation. One advantage of monocular analysis of the fluorescence detectors is a lower energy threshold for cosmic rays than that of other techniques like stereoscopic observations or coincidences with the surface detector array, allowing the measurement of an energy spectrum covering three orders of magnitude in energy. Analyzing data collected during those seven years, we report the energy spectrum of cosmic rays covering a broad range of energies above 10^17.2eV measured by the fluorescence detectors and a comparison with previously published results.Found in: ključnih besedahKeywords: Cosmic rays, Ultra-high energy, Fluorescence detector, Energy spectrum, Ankle, GZK cutoffPublished: 27.04.2020; Views: 1560; Downloads: 0 Fulltext (1,23 MB) 16.The hybrid energy spectrum of Telescope Array’s Middle Drum Detector and surface arrayJ. P. Lundquist, R.U. Abbasi, 2015, original scientific articleAbstract: The Telescope Array experiment studies ultra high energy cosmic rays using a hybrid detector. Fluorescence telescopes measure the longitudinal development of the extensive air shower generated when a primary cosmic ray particle interacts with the atmosphere. Meanwhile, scintillator detectors measure the lateral distribution of secondary shower particles that hit the ground. The Middle Drum (MD) fluorescence telescope station consists of 14 telescopes from the High Resolution Fly’s Eye (HiRes) experiment, providing a direct link back to the HiRes measurements. Using the scintillator detector data in conjunction with the telescope data improves the geometrical reconstruction of the showers significantly, and hence, provides a more accurate reconstruction of the energy of the primary particle. The Middle Drum hybrid spectrum is presented and compared to that measured by the Middle Drum station in monocular mode. Further, the hybrid data establishes a link between the Middle Drum data and the surface array. A comparison between the Middle Drum hybrid energy spectrum and scintillator Surface Detector (SD) spectrum is also shown.Found in: ključnih besedahKeywords: Cosmic rays, Energy spectrum, Telescope Array, Hybrid, Ultra high energyPublished: 27.04.2020; Views: 1491; Downloads: 0 Fulltext (3,12 MB) 17.Indications of Proton-Dominated Cosmic-Ray Composition above 1.6 EeVJ. P. Lundquist, R.U. Abbasi, 2010, original scientific articleAbstract: We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (Xmax), for air shower events collected by the High-Resolution Fly’s Eye (HiRes) observatory. The HiRes data are consistent with a constant elongation rate d⟨Xmax⟩/d[log(E)] of 47.9 ± 6.0 (stat) ± 3.2 (syst) g/cm^2/decade for energies between 1.6 and 63 EeV, and are consistent with a predominantly protonic composition of cosmic rays when interpreted via the QGSJET01 and QGSJET-II high-energy hadronic interaction models. These measurements constrain models in which the galactic-to-extragalactic transition is the cause of the energy spectrum ankle at 4×10^18 eV.Found in: ključnih besedahSummary of found: ...We report studies of ultrahigh- energy cosmic-ray composition via analysis of depth of... ...transition is the cause of the energy spectrum ankle at 4×10^18 eV....Keywords: Cosmic rays, Energy spectrum, Telescope Array, Hybrid, Ultra high energyPublished: 27.04.2020; Views: 1519; Downloads: 0 Fulltext (314,89 KB) 18.Supergalactic Structure of Energy-Angle CorrelationsP. Sokolsky, J. P. Lundquist, 2020, published scientific conference contributionAbstract: Evidence for the supergalactic structure of multiplets (energy-angle correlations) has previously been shown using ultra-high energy cosmic ray (UHECR) data from Telescope Array (TA) with energies above 10^19 eV. The supergalactic deflection hypothesis (that UHECR sources and intervening magnetic fields are correlated) is measured by the all-sky behavior of the strength of intermediate-scale correlations. The multiplets are measured in spherical surface wedge bins of the field-of-view to account for uniform and random magnetic fields. The structure found is consistent with the previously published energy spectrum anisotropy results of TA and toy-model simulations of a supergalactic magnetic sheet. The 7 year data post-trial significance of this feature appearing by chance, on an isotropic sky, was found by Monte Carlo simulation to be ∼4σ. The analysis has now been applied to 10 years of data.Found in: ključnih besedahSummary of found: ...is consistent with the previously published energy spectrum anisotropy results of TA and toy-model simulations...Keywords: Cosmic rays, UHECR, energy spectrum, magnetic deflection, large-scale structure, supergalactic, multipletsPublished: 27.04.2020; Views: 1467; Downloads: 54 Fulltext (1,66 MB) 19.Supergalactic Structure of Multiplets with the Telescope Array Surface DetectorP. Sokolsky, J. P. Lundquist, 2019, published scientific conference contributionAbstract: Evidence of supergalactic structure of multiplets has been found for ultra-high energy cosmic rays (UHECR) with energies above 10^19 eV using 7 years of data from the Telescope Array (TA) surface detector. The tested hypothesis is that UHECR sources, and intervening magnetic fields, may be correlated with the supergalactic plane, as it is a fit to the average matter density within the GZK horizon. This structure is measured by the average behavior of the strength of intermediate-scale correlations between event energy and position (multiplets). These multiplets are measured in wedge-like shapes on the spherical surface of the fieldof-view to account for uniform and random magnetic fields. The evident structure found is consistent with toy-model simulations of a supergalactic magnetic sheet and the previously published Hot/Coldspot results of TA. The post-trial probability of this feature appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be ~4.5σ.Found in: ključnih besedahSummary of found: ...of multiplets has been found for ultra-high energy cosmic rays (UHECR) with energies above 10^19... ...UHECR, cosmic rays, energy spectrum, anisotropy, large-scale structure, magnetic deflection...Keywords: UHECR, cosmic rays, energy spectrum, anisotropy, large-scale structure, magnetic deflectionPublished: 28.04.2020; Views: 1608; Downloads: 99 Fulltext (1,38 MB) 20.Evidence of Intermediate-Scale Energy Spectrum Anisotropy in the Northern Hemisphere from Telescope ArrayJ. P. Lundquist, 2018, published scientific conference contributionAbstract: Evidence of an energy dependent intermediate-scale anisotropy has been found in the arrival directions of ultra-high energy cosmic rays in the northern hemisphere, using 7 years of TA surface detector data. The previously reported hot spot" excess E ≥ 10^19.75 EeV is found to correspond to a deficit, or cold spot," of events for 10^19.2≤ E < 10^19.75 EeV. This feature suggests energy dependent magnetic deflection of cosmic-rays. The global post-trial significance of the energy spectrum deviation is found to be 3.74σ.Found in: ključnih besedahKeywords: UHECR, cosmic rays, energy spectrum, anisotropy, magnetic deflectionPublished: 28.04.2020; Views: 1530; Downloads: 50 Fulltext (4,87 MB)
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