51. Cosmic Ray Composition between 2 PeV and 2 EeV measured by the TALE Fluorescence DetectorT. AbuZayyad, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: The Telescope Array (TA) cosmic rays detector located in the State
of Utah in the United States is the largest ultra high energy cosmic rays
detector in the northern hemisphere. The Telescope Array Low Energy Extension
(TALE) fluorescence detector (FD) was added to TA in order to lower the
detector's energy threshold, and has succeeded in measuring the cosmic rays
energy spectrum down to PeV energies, by making use of the direct Cherenkov
light produced by air showers. In this contribution we present the results
of a measurement of the cosmic-ray composition using TALE FD data collected
over a period of ∼7 years. TALE FD data is used to measure the Xmax distributions of showers seen in the energy range of 10^15.3 - 10^18.3 eV. The data distributions are fit to Monte Carlo distributions of {H, He, N, Fe} cosmic-ray primaries for energies up to 10^18 eV. Mean Xmax values are measured for the full energy range. TALE observes a light composition at the "Knee", that gets gradually heavier as energy increases toward the "Second-Knee". An increase in the Xmax elongation rate is observed at energies just above 10^17.3 eV indicating a change in the cosmic rays composition from a heavier to a lighter mix of primaries.
Keywords: Telescope Array, TALE, low energy extension, indirect detection, fluorescence detection, cerenkov light, ultra-high energy, cosmic rays, composition
Published in RUNG: 02.10.2023; Views: 651; Downloads: 5
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52. Cosmic Ray Energy Spectrum measured by the TALE Fluorescence DetectorT. AbuZayyad, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: The Telescope Array (TA) cosmic rays detector located in the State
of Utah in the United States is the largest ultra high energy cosmic rays
detector in the northern hemisphere. The Telescope Array Low Energy Extension
(TALE) fluorescence detector (FD) was added to TA in order to lower the
detector's energy threshold, and has succeeded in measuring the cosmic rays
energy spectrum down to PeV energies, by making use of the direct Cherenkov
light produced by air showers. In this contribution we present the results
of a measurement of the cosmic-ray energy spectrum using TALE FD data
collected over a period of ∼7 years. The data set used for this
measurement is the same one used for the mass composition measurement that is
presented, as a separate contribution, at this conference. The energy
spectrum shows features consistent with the "knee" and the "second knee"; a
similar result to our previous energy spectrum publication. This time
using a different hadronic model, and different event selection criteria as
explained in the text of this proceeding.
Keywords: Telescope Array, TALE, low energy extension, indirect detection, fluorescence detection, cerenkov light, ultra-high energy, cosmic rays, energy spectrum
Published in RUNG: 02.10.2023; Views: 514; Downloads: 6
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53. Cosmic Ray Composition in the Second Knee Region as Measured by the TALE Hybrid DetectorR. Abbasi, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: The Telescope Array Low-energy Extension (TALE) experiment is a hybrid air shower detector for the observation of air showers induced by cosmic rays with energy above 10^16 eV. The TALE detector consists of a Fluorescence Detector (FD) station with 10 FD telescopes located at the TA Middle Drum FD Station (itself made up of 14 FD telescopes), and a Surface Detector (SD) array made up of 80 scintillation counters, including 40 with 400 m spacing and 40 with 600 m spacing. A triggering system for the TALE-SD using an external trigger from the TALE-FD, a so-called hybrid trigger, allows for a lower energy threshold. The TALE hybrid trigger system has been working since 2018. Here we present an estimate of the performance of hybrid detection using a Monte Carlo simulation, and a first measurement of the cosmic ray composition and spectrum using the TALE-Hybrid detector.
Keywords: Telescope Array, TALE, low energy extension, indirect detection, hybrid detection, ground array, fluorescence detection, cerenkov light, ultra-high energy, cosmic rays, energy spectrum, composition
Published in RUNG: 02.10.2023; Views: 633; Downloads: 5
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54. The UHECR dipole and quadrupole in the latest data from the original Auger and TA surface detectorsP. Tinyakov, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, published scientific conference contribution Abstract: The sources of ultra-high-energy cosmic rays are still unknown, but assuming standard physics, they are expected to lie within a few hundred megaparsecs from us. Indeed, over cosmological distances cosmic rays lose energy to interactions with background photons, at a rate depending on their mass number and energy and properties of photonuclear interactions and photon backgrounds. The universe is not homogeneous at such scales, hence the distribution of the arrival directions of cosmic rays is expected to reflect the inhomogeneities in the distribution of galaxies; the shorter the energy loss lengths, the stronger the expected anisotropies. Galactic and intergalactic magnetic fields can blur and distort the picture, but the magnitudes of the largest-scale anisotropies, namely the dipole and quadrupole moments, are the most robust to their effects. Measuring them with no bias regardless of any higher-order multipoles is not possible except with full-sky coverage. In this work, we achieve this in three energy ranges (approximately 8-16 EeV, 16-32 EeV, and 32-∞ EeV) by combining surface-detector data collected at the Pierre Auger Observatory until 2020 and at the Telescope Array (TA) until 2019, before the completion of the upgrades of the arrays with new scintillator detectors. We find that the full-sky coverage achieved by combining Auger and TA data reduces the uncertainties on the north-south components of the dipole and quadrupole in half compared to Auger-only results.
Keywords: Pierre Auger Observatory, Telescope Array, indirect detection, surface detection, ultra-high energy, cosmic rays, anisotropy, large scale, fully sky coverage, dipole, quadropole
Published in RUNG: 29.09.2023; Views: 634; Downloads: 4
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55. Mass composition of Telescope Array's surface detectors events using deep learningI. Kharuk, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: We report on an improvement of deep learning techniques used for identifying primary particles of atmospheric air showers. The progress was achieved by using two neural networks. The first works as a classifier for individual events, while the second predicts fractions of elements in an ensemble of events based on the inference of the first network. For a fixed hadronic model, this approach yields an accuracy of 90% in identifying fractions of elements in an ensemble of events.
Keywords: Telescope Array, indirect detection, ground array, surface detection, ultra-high energy, cosmic rays, composition, deep learning, machine learning, neural networks
Published in RUNG: 29.09.2023; Views: 711; Downloads: 4
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56. Telescope Array anisotropy summaryI. Tkachev, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: In this talk, we summarise the results of recent anisotropy studies conducted by the Telescope Array (TA) collaboration. At largest scales we test the TA data for the presence of a dipole. On smaller scales, an update on the excess of events in the direction of Ursa Major previously found in the TA data will be presented. These flux variations may trace the distribution of UHECR sources. We will examine the data for correlations with large-scale structures in the nearby Universe, and as a result, hints for the chemical composition of primaries will be provided. We also discuss a related anisotropy of the UHECR spectrum.
Keywords: Telescope Array, indirect detection, ground array, surface detection, ultra-high energy, cosmic rays, composition, energy spectrum, anisotropy
Published in RUNG: 29.09.2023; Views: 526; Downloads: 4
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57. Effects of Galactic magnetic field on the UHECR anisotropy studiesR. Higuchi, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: Telescope Array (TA) and Auger experiments reported anisotropies in the arrival direction of ultrahigh-energy cosmic rays (UHECRs). In particular, Auger Collaboration reported a correlation
between UHECR events and the flux model of assumed sources and suggested a contribution of
starburst galaxies (SBGs) to the anisotropy of UHECRs. However, in their study, the effect of
coherent deflections by the galactic magnetic field (GMF) is not taken into account. In this study, we investigated the effect of the GMF on the arrival directions of UHECRs using the cosmic ray propagation code CRPropa3. We used a backtracking technique which consists of propagating antiparticles to map the flux outside the galaxy to at the earth. We estimate the systematic effects caused by GMF in the reported likelihood analysis. We conduct likelihood analysis for mock UHECR datasets based on the flux pattern through the GMF model. We found systematic decrease of (f_ani, �) due to GMF. As prospects for the TAx4 experiment and joint analysis of Auger and TA collaborations, we develop the likelihood analysis method with the convolution of the rigidity spectrum.
Keywords: Telescope Array, TAx4, ultra-high energy, cosmic rays, anisotropy, galactic magnetic field, starburst galaxies
Published in RUNG: 29.09.2023; Views: 607; Downloads: 5
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58. Performance and simulation of the surface detector array of the TAx4 experimentK. Fujisue, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: The TAx4 experiment is a project to observe highest energy cosmic rays by expanding the detectionarea of the Telescope Array (TA) experiment with newly constructed surface detectors (SDs) andfluorescence detectors (FDs). New SDs are arranged in a square grid with 2.08 km spacing atthe north east and south east of the TA SD array. We use CORSIKA simulations and implementthe calibration data of the new SDs to calculate the performance of the new SDs. We comparethe data with the simulation and validate the performance of the SDs. The comparison and theperformance will be shown in the presentation.
Keywords: Telescope Array, TAx4, indirect detection, ground array, surface detection, ultra-high energy, cosmic rays, CORSIKA
Published in RUNG: 29.09.2023; Views: 549; Downloads: 5
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59. Highlights from the Telescope Array experimentGrigory I. Rubtsov, R. U. Abbasi, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2022, published scientific conference contribution (invited lecture) Abstract: The Telescope Array (TA) is the largest cosmic ray observatory in the Northern Hemisphere. It is designed to measure the properties of cosmic rays over a wide range of energies. TA with it's low energy extension (TALE) observe cosmic-ray induced extensive air showers between 2 PeV and 100 EeV in hybrid mode using multiple instruments, including an array of scintillator detectors at the Earth's surface and telescopes to measure the fluorescence and Cerenkov light. The statistics at the highest energies is being enhanced with the ongoing construction of the TAx4 experiment which will quadruple the surface area of the detector. We review the present status of the experiments and most recent physics results on the cosmic ray anisotropy, chemical composition and energy spectrum. Notable highlights include a new feature in the energy spectrum at about 10^19.2 eV, and a new clustering of events in the direction of Perseus-Pisces supercluster above this energy. We also report on updated diffuse photon flux limits and new spectrum and composition results in the lower energy range from the TALE extension.
Keywords: Telescope Array, TALE, low energy extension, TAx4, indirect detection, hybrid detection, ground array, fluorescence detection, Cherenkov light, ultra-high energy, cosmic rays, energy spectrum, composition, anisotropy
Published in RUNG: 26.09.2023; Views: 632; Downloads: 5
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60. Performance study update of observations in divergent mode for the Cherenkov Telescope ArrayA. Donini, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution Abstract: Due to the limited field of view (FoV) of Cherenkov telescopes, the time needed to achieve target sensitivity for surveys of the extragalactic and Galactic sky is large. To optimize the time spent to perform such surveys, a so-called “divergent mode” of the Cherenkov Telescope Array Observatory (CTAO) was proposed as an alternative observation strategy to the traditional parallel pointing. In the divergent mode, each telescope points to a position in the sky that is slightly offset, in the outward direction, from the original center of the field of view. This bring the advantage of increasing the total instantaneous arrays’ FoV. From an enlarged field of view also benefits the search for very-high-energy transient sources, making it possible to cover large sky regions in follow-up observations, or to quickly cover the probability sky map in case of Gamma Ray Bursts (GRB), Gravitational Waves (GW), and other transient events. In this contribution, we present the proposed implementation of the divergent pointing mode and its first preliminary performance estimation for the southern CTAO array.
Keywords: Cherenkov Telescope Array, CTAO, divergent mode, very-high-energy transient sources
Published in RUNG: 26.09.2023; Views: 592; Downloads: 5
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