1. Search for evidence of neutron fluxes using Pierre Auger Observatory dataDanelise de Oliveira Franco, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci Opis: Astrophysical neutral particles, such as neutrons, can point directly to their sources since they are not affected by magnetic fields. We expect neutron production in the immediate vicinity of the acceleration sites due to cosmic ray interactions. Hence, a high-energy neutron flux could help to identify sources of cosmic rays in the EeV range. Free neutrons, although unstable, can travel a mean distance of 9.2 kpc times their energy in EeV. Due to the neutron instability, we limit the searches to Galactic candidate sources. Since air showers initiated by a neutron are indistinguishable from those generated by a proton, we would recognize a neutron flux as an
excess of events from the direction of its source. Previous searches using events with a zenith angle up to 60^◦ and energies above 1 EeV found no surplus of events that would indicate a neutron flux. We present the results of the search for evidence of high-energy neutron fluxes using a data set about three times larger than the previous work. We investigate the sky in the field of view of the Pierre Auger Observatory, narrowing down to specific directions of candidate sources. With respect to previous works, we extend the angular range up to zenith angles of 80^◦ , reaching declinations from −90^◦ to +45^◦ , and the energy range going as low as 0.1 EeV. The extension in the field of view provides exposure to the Crab Nebula for the first time. Ključne besede: neutrons, cosmic ray, Pierre Auger Observatory, Crab Nebula, proton, high-energy neutron flux Objavljeno v RUNG: 14.11.2023; Ogledov: 257; Prenosov: 4
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2. AugerPrime surface detector electronicsA. Abdul Halim, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, izvirni znanstveni članek Opis: Operating since 2004, the Pierre Auger Observatory has led to major advances in our
understanding of the ultra-high-energy cosmic rays. The latest findings have revealed new insights that led to the upgrade of the Observatory, with the primary goal of obtaining information on the primary mass of the most energetic cosmic rays on a shower-by-shower basis. In the framework of the upgrade, called AugerPrime, the 1660 water-Cherenkov detectors of the surface array are equipped with plastic scintillators and radio antennas, allowing us to enhance the composition sensitivity. To accommodate new detectors and to increase experimental capabilities, the electronics
is also upgraded. This includes better timing with up-to-date GPS receivers, higher sampling
frequency, increased dynamic range, and more powerful local processing of the data. In this paper, the design characteristics of the new electronics and the enhanced dynamic range will be described. The manufacturing and test processes will be outlined and the test results will be discussed. The calibration of the SD detector and various performance parameters obtained from the analysis of the first commissioning data will also be presented. Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, AugerPrime detector upgrade, surface detector array, surface detector electronics Objavljeno v RUNG: 18.10.2023; Ogledov: 347; Prenosov: 4
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3. Highlights from the Telescope Array ExperimentJ. Kim, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci (vabljeno predavanje) Opis: The Telescope Array (TA) is the largest ultra-high energy cosmic ray (UHECR) observatory in the Northern Hemisphere. Together with the TA Low Energy Extension (TALE), TA×4, and TALE infill detector, the TA measures the properties of UHECR-induced extensive air showers (EAS) in the energy region from 10^15 eV to over 10^20 eV. Each of these uses a hybrid system with an array of scintillators to sample the footprint of the EAS at the Earth’s surface along with telescopes that measure the fluorescence and Cherenkov light from the EAS. The statistics at the highest energies are being enhanced with the TA×4 detector, half completed but still under construction, which will quadruple the surface detector area with telescopes. The TALE infill surface detectors were recently deployed to further lower the hybrid energy threshold of TALE. We present the status of the experiment and recent results on the energy spectrum, mass composition, and anisotropy, including new features in the energy spectrum at about 10^19.2 eV and in the UHECR arrival direction anisotropy. Ključne besede: Telescope Array, TALE, low energy extension, TAx4, indirect detection, hybrid detection, ground array, surface detection, fluorescence detection, cerenkov light, ultra-high energy, cosmic rays, energy spectrum, composition, anisotropy Objavljeno v RUNG: 10.10.2023; Ogledov: 294; Prenosov: 6
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4. Measurement of cosmic-ray proton and helium spectra from the ISS-CREAM experimentG. Choi, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci Opis: The Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM) experiment successfully recorded data for 539 days from Aug. 2017 to Feb. 2019. The ISS-CREAM instrument consists of a Silicon Charge Detector (SCD), carbon targets, a calorimeter (CAL), a top counting detector (TCD), a bottom counting detector (BCD), and a boronated scintillator detector (BSD). In this analysis, the SCD was used for the charge measurements. It comprises four layers, and each SCD layer is finely segmented with 2,688 silicon pixels to minimize charge misidentification due to the backscattered particles. The CAL was used for the energy measurements. It comprises 20 layers of tungsten/scintillating fibers. Each tungsten/scintillating-fiber layer consists of a 50 cm × 50 cm × 3.5 mm tungsten plate, followed by a layer of fifty 1 cm-wide 50 cm-long scintillating-fiber ribbons. The CAL also provides the incident cosmic-ray track and the high-energy trigger. For the low-energy trigger, the TCD and BCD were used. In this paper, we present the proton spectrum from the ISS-CREAM experiment in the energy range of 1.6 - 655 TeV and the preliminary helium spectrum in the energy range of 2.7 TeV - 1.1 PeV Ključne besede: ISS-CREAM, silicon charge detector, calorimeter, direct detection, high energy, cosmic rays, energy spectrum, composition, proton, helium Objavljeno v RUNG: 10.10.2023; Ogledov: 280; Prenosov: 5
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5. Effect of optical properties of FDs on reconstruction analysisD. Sato, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci Opis: The TA experiment uses fluorescence telescopes to observe cosmic ray air showers. The telescope camera uses PMTs as Pixels. The telescope’s PMT pointing direction has an uncertainty of 0.1°, and more precise measurements of the telescope's optical properties are needed to more accurately reconstruct the cosmic ray air showers. We have developed the Opt-copter which is a light source mounted on a drone that can be flown within the telescope's field of view. Observational experiments with the Opt-copter have provided a more accurate analysis of the telescope viewing direction.
In this study, we estimate the effect of this measurement of accurate telescope viewing direction on the reconstruction of cosmic ray air showers. Ključne besede: Telescope Array, indirect detection, fluorescence detection, ultra-high energy, cosmic rays, composition, calibration, Xmax Objavljeno v RUNG: 10.10.2023; Ogledov: 291; Prenosov: 6
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6. Effects of atmospheric transparency on TA air shower analysisK. Mizuno, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci Opis: The Telescope Array (TA) experiment continues to observe Ultra High Energy Cosmic Rays (UHECRs) both with its original TA detectors as well as with the new TAx4 expansion detectors. These observations employ Fluorescence Detectors (FDs) to capture the air shower induced by the primary UHECRs. The FD observes fluorescence light emitted from atmospheric nitrogen molecules excited by air shower particles. Observation of the FD extends over tens of kilometers, and the fluorescence light is attenuated by scattering from atmospheric molecules and aerosols during the propagation process. Seasonal dependence was found when evaluating the attenuation of fluorescence by aerosols. We will report on the effects of this seasonal dependence on TA air shower analysis. Ključne besede: Telescope Array, TAx4, indirect detection, fluorescence detection, ultra-high energy, cosmic rays, atmosphere, calibration, VAOD Objavljeno v RUNG: 10.10.2023; Ogledov: 296; Prenosov: 6
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7. Updates of the surface detector array of the TAx4 experimentE. Kido, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci Opis: The TAx4 experiment plans to realize an Ultra High Energy Cosmic Rays (UHECR) detection area four times larger than that of the TA experiment. TAx4 will include five hundreds new surface detectors (SD) spaced at 2.08 km and two new fluorescence detectors (FD), which provides hybrid observation of UHECRs. We deployed 257 SDs in 2019 and completed building 2 FD stations in 2020, all operating stably. The data acquisition of the SDs is made via six communication towers, and inter-tower triggers have been recently implemented. Ključne besede: Telescope Array, TAx4, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays Objavljeno v RUNG: 10.10.2023; Ogledov: 282; Prenosov: 6
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8. Anisotropies in the arrival direction distribution of ultra-high energy cosmic rays measured by the Telescope Array surface detectorJ. Kim, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci Opis: Ultra-high energy cosmic rays (UHECRs) are extremely energetic, charged particles with energies greater than 10^18 eV, originating from outer space. We investigate anisotropic patterns in the arrival direction distribution of UHECRs to identify their source locations. The Telescope Array (TA) experiment, the largest UHECR observatory in the northern hemisphere, has observed evidence of two intermediate-scale anisotropies in UHECR arrival direction distributions: the TA Hotspot and the Perseus-Pisces supercluster excess. In this presentation, we will describe an oversampling analysis that we performed to find the excess of events using the data measured by the TA surface detector array. We will report the latest results of the TA Hotspot and Perseus-Pisces supercluster excesses. Ključne besede: Telescope Array, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, anisotropy, hotspot Objavljeno v RUNG: 10.10.2023; Ogledov: 282; Prenosov: 4
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9. High-speed Video Camera Observations Associated with a Terrestrial Gamma-ray Flash at the Telescope Array DetectorR. Abbasi, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci Opis: This work presents observations of the optical emission of a lightning flash in conjunction with a downward-directed Terrestrial Gamma-ray Flash (TGF) at the Telescope Array detector. Previously in ICRC-2021, we reported joint observations by the Telescope Array Surface Detector (TASD), the Lightning Mapping Array, a sferic sensor, and a broadband interferometer of particle showers in coincidence with lightning. These observations consisted of energetic showers of approximately less than 10-microsecond duration with footprints on the ground of 3-6 kilometers in diameter, originating in the first one to two milliseconds of downward lightning leaders and in coincidence with the initial breakdown pulses stage of negative cloud-to-ground lighting leaders. Scintillator waveform and simulation studies confirmed that these showers must consist primarily of gamma radiations.
In this work, we use the TASD detector, together with a high-speed video camera, in conjunction with multiple lightning instruments at the TASD site, to report on the optical emission associated with a downward-directed terrestrial gamma-ray flash. Results from this study allow us to further
the understanding of the initiation and propagation mechanism of terrestrial gamma-ray flashes. It will also further our ability to compare the most recent satellite optical emissions counterpart of upward-directed TGFs to that of downward-directed TGFs. Ključne besede: Telescope Array, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, Lightning Mapping Array, gamma-ray flashes, photons Objavljeno v RUNG: 10.10.2023; Ogledov: 271; Prenosov: 5
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10. Measurement of cosmic-ray energy spectrum with the TALE detector in hybrid modeH. Oshima, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci Opis: The TA Low-energy Extension (TALE) experiment extends the low-energy side of the TA experiment below 10^15 eV. A main objective of TALE is to study the transition from galactic to extragalactic cosmic rays. The TALE detector is a hybrid observatory composed of fluorescence telescopes and a surface detector array of scintillation counters. The surface detectors are arranged with inter-counter spacing of 400 and 600 meters, suitable for hybrid energy spectrum measurements in the low-energy region. We measured the energy spectrum using data collected during 429 hours of observation by the TALE hybrid detector. This energy spectrum measurement will play an important role in understanding the transition from cosmic rays of galactic origin to those of extragalactic origin. Ključne besede: Telescope Array, TALE, low energy extension, indirect detection, hybrid detection, ground array, fluorescence detection, cerenkov light, ultra-high energy, cosmic rays, energy spectrum Objavljeno v RUNG: 10.10.2023; Ogledov: 266; Prenosov: 4
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