1. An extremely energetic cosmic ray observed by a surface detector arrayR. U. Abbasi, M. Allen, R. Arimura, J. W. Belz, Douglas R. Bergman, S. A. Blake, K. Shin, I. J. Buckland, B. G. Cheon, Jon Paul Lundquist, 2023, original scientific article Abstract: Cosmic rays are energetic charged particles from extraterrestrial sources, with the highest-energy events thought to come from extragalactic sources. Their arrival is infrequent, so detection requires instruments with large collecting areas. In this work, we report the detection of an extremely energetic particle recorded by the surface detector array of the Telescope Array experiment. We calculate the particle’s energy as 244 +- 29 (stat.) +51,-76 (syst.)
exa–electron volts (~40 joules). Its arrival direction points back to a void in the large-scale structure of the Universe. Possible explanations include a large deflection by the foreground magnetic field, an unidentified source in the local extragalactic neighborhood, or an incomplete knowledge of particle physics.
Keywords: ultra-high-energy cosmic rays, telescope array, extremely energetic cosmic-ray event
Published in RUNG: 23.04.2025; Views: 154; Downloads: 0
 Link to file
This document has many files! More... |
2. Mass composition of ultrahigh energy cosmic rays from distribution of their arrival directions with the Telescope ArrayR. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Y. Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2024, original scientific article Abstract: We use a new method to estimate the injected mass composition of ultrahigh cosmic rays (UHECRs) at energies higher than 10 EeV. The method is based on comparison of the energy-dependent distribution of cosmic ray arrival directions as measured by the Telescope Array (TA) experiment with that calculated in a given putative model of UHECR under the assumption that sources trace the large-scale structure (LSS) of the Universe. As we report in the companion Letter, the TA data show large deflections with respect to the LSS which can be explained, assuming small extragalactic magnetic fields (EGMF), by an intermediate composition changing to a heavy one (iron) in the highest energy bin. Here we show that these results are robust to uncertainties in UHECR injection spectra, the energy scale of the experiment and galactic magnetic fields. The assumption of weak EGMF, however, strongly affects this interpretation at all but the highest energies E > 100 EeV, where the remarkable isotropy of the data implies a heavy injected composition even in the case of strong EGMF. This result also holds if UHECR sources are as rare as 2 × 10[sup]−5 Mpc[sup]−3, that is the conservative lower limit for the source number density.
Keywords: ultrahigh energy cosmic rays, large-scale structure, extragalactic magnetic fields, UHECR propagation, Telescope Array, UHECR mass composition, UHECR arrival directions
Published in RUNG: 23.04.2025; Views: 128; Downloads: 0
Link to file
This document has many files! More... |
3. Measurement of UHECR energy spectrum with the Pierre Auger Observatory and the Telescope ArrayDouglas R. Bergman, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: The measurement of the energy spectrum of ultra-high-energy cosmic rays (UHECRs) is of crucial importance to clarify their origin, acceleration mechanisms, and propagation processes in inter-Galactic and Galactic space. The Pierre Auger Observatory in Argentina and the Telescope Array (TA) in the US have reported their measurements of UHECR energy spectra observed in the southern and northern hemisphere, respectively. The Auger–TA energy spectrum working group
was established in 2012 and has been working to understand the uncertainties in energy scale in both experiments, their systematic differences, and differences in the shape of the spectra. In previous works, we reported that there was an overall agreement of the energy spectra measured by the two observatories below 10 EeV while at higher energies, a remaining significant difference was observed in the common declination band. This time we revisit the energy scales of both experiments, including the fluorescence yield and the invisible energy corrections. Another new approach to investigate a possible source of energy systematic difference is to reconstruct simulated showers of common energy and zenith angle using the detector simulation and reconstruction programs of both experiments that are independently tuned and optimized for data from their own
detectors. The results will be presented at the conference.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, Telescope Array, energy spectrum
Published in RUNG: 23.01.2024; Views: 2170; Downloads: 6
 Full text (731,82 KB)
This document has many files! More... |
4. Measurement of cosmic-ray proton and helium spectra from the ISS-CREAM experimentG. H. Choi, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: 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
Keywords: Telescope Array, TAx4, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2420; Downloads: 9
Full text (1,72 MB)
This document has many files! More... |
5. Effect of optical properties of FDs on reconstruction analysisDaiki Sato, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, 2023, published scientific conference contribution Abstract: 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.
Keywords: Telescope Array, indirect detection, fluorescence detection, ultra-high energy, cosmic rays, composition, calibration, Xmax
Published in RUNG: 10.10.2023; Views: 2591; Downloads: 9
Full text (670,84 KB)
This document has many files! More... |
6. Effects of atmospheric transparency on Telescope Array air shower analysisK. Mizuno, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: 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.
Keywords: Telescope Array, TAx4, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2546; Downloads: 10
Full text (1,16 MB)
This document has many files! More... |
7. Updates of the surface detector array of the TAx4 experimentEiji Kido, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: 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.
Keywords: Telescope Array, TAx4, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2046; Downloads: 11
Full text (2,39 MB)
This document has many files! More... |
8. Anisotropies in the arrival direction distribution of ultra-high energy cosmic rays measured by the Telescope Array surface detectorJihyun Kim, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: 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.
Keywords: Telescope Array, TALE, low energy extension, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2126; Downloads: 6
Full text (9,49 MB)
This document has many files! More... |
9. High-speed video camera observations associated with a terrestrial gamma-ray flash at the Telescope Array DetectorR. Abbasi, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: 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.
Keywords: Telescope Array, low energy extension, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2038; Downloads: 6
Full text (2,91 MB)
This document has many files! More... |
10. Measurement of cosmic-ray energy spectrum with the TALE detector in hybrid modeH. Oshima, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: 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.
Keywords: Telescope Array, TALE, low energy extension, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2643; Downloads: 6
Full text (3,33 MB)
This document has many files! More... |
