Yuya Oku

Osaka Electro-Communication University

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Y. Tameda

Osaka Electro-Communication University

Y. Tsunesada

Osaka Metropolitan University

M. Kuznetsov

Institute for Nuclear Research

Ryuji Takeishi

The University of Tokyo

K. Fujita

The University of Tokyo

O. Kalashev

Institute for Nuclear Research

МС

М. С. Пширков

Institute for Nuclear Research

Jon Paul Lundquist

University of Nova Gorica

T. Nonaka

The University of Tokyo

M. Tanaka

High Energy Accelerator Research Organization

Cooperative Institutions

Consejo Nacional de Investigaciones Científicas y Técnicas

527

Instituto de Tecnologías en Detección y Astropartículas

445

University of Buenos Aires

419

Universidad Nacional de La Plata

417

National University of General San Martín

389

Pierre Auger Observatory

377

Institute of Astronomy and Space Physics

377

National Technological University

374

Institute of Scientific and Technical Research for Defense

271

The University of Tokyo

201

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Joint analysis of the energy spectrum of ultra-high-energy cosmic rays as measured at the Pierre Auger Observatory and the Telescope Array

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019) (2021)

Y. Tsunesada Rasha Abbasi T. Abu‐Zayyad Monica Allen Yuto Arai

The measurement of the energy spectrum of ultra-high-energy cosmic rays (UHECRs) is of crucial importance to clarify their origin and acceleration mechanisms. 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 region of the sky accessible to both Observatories ($[-15,+24]$ degrees in declination) can be used to cross-calibrate the two spectra. The Auger-TA energy spectrum working group was organized 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. We revisit this issue to understand its origin by examining the systematic uncertainties, statistical effects, and other possibilities. We will also discuss the differences in the spectra in different declination bands and a new feature in the spectrum recently reported by the Auger Collaboration.

Pierre Auger Observatory

Right ascension

10.22323/1.395.0337

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The UHECR dipole and quadrupole in the latest data from the original Auger and TA surface detectors

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019) (2021)

P. Tinyakov Rogério de Almeida Rasha Abbasi T. Abu‐Zayyad Monica Allen

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--$\infty$ 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.

Pierre Auger Observatory

10.22323/1.395.0375

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First High‐Speed Video Camera Observations of a Lightning Flash Associated With a Downward Terrestrial Gamma‐Ray Flash

Geophysical Research Letters (2023)

Rasha Abbasi Marcelo M. F. Saba John Belz P. R. Krehbiel W. Rison

Abstract In this paper, we present the first high‐speed video observation of a cloud‐to‐ground lightning flash and its associated downward‐directed Terrestrial Gamma‐ray Flash (TGF). The optical emission of the event was observed by a high‐speed video camera running at 40,000 frames per second in conjunction with the Telescope Array Surface Detector, Lightning Mapping Array, interferometer, electric‐field fast antenna, and the National Lightning Detection Network. The cloud‐to‐ground flash associated with the observed TGF was formed by a fast downward leader followed by a very intense return stroke peak current of −154 kA. The TGF occurred while the downward leader was below cloud base, and even when it was halfway in its propagation to ground. The suite of gamma‐ray and lightning instruments, timing resolution, and source proximity offer us detailed information and therefore a unique look at the TGF phenomena.

Lightning

Lightning detection

Upper-atmospheric lightning

10.1029/2023gl102958

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Intermediate Fluence Downward Terrestrial Gamma Ray Flashes as Observed by the Telescope Array Surface Detector

Journal of Geophysical Research Atmospheres (2024)

Rasha Abbasi N. Kieu P. R. Krehbiel J. W. Belz Marcelo M. F. Saba

Abstract On 11 September 2021, two small thunderstorms developed over the Telescope Array Surface Detector (TASD) that produced an unprecedented number of six downward terrestrial gamma ray flashes (TGFs) within one‐hour timeframe. The TGFs occurred during the initial stage of negative cloud‐to‐ground flashes whose return strokes had increasingly large peak currents up to 223 kA, 147 GeV energy deposit in up to 25 1.2 km‐spaced surface detectors, and intermittent bursts of gamma‐rays with total durations up to 717 s. The analyses are based on observations recorded by the TASD network, complemented by data from a 3D lightning mapping array, broadband VHF interferometer, fast electric field change sensor, high‐speed video camera, and the National Lightning Detection Network. The TGFs of the final two flashes had gamma fluences of and 8, logarithmically bridging the gap between previous TASD and satellite‐based detections. The observations further emphasize the similarity between upward and downward TGF varieties, suggesting a common mechanism for their production.

10.1029/2024jd041260

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A study of analysis method for the identification of UHECR source type

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019) (2021)

Fugo Yoshida Rasha Abbasi T. Abu‐Zayyad Monica Allen Yuto Arai

The autocorrelation analysis using the arrival direction of Ultra High Energy Cosmic Rays (UHECRs) has been previously reported by the Telescope Array (TA) experiment. It is expected that the autocorrelation function reflects the source distribution. We simulate the expected arrival direction distribution of the cosmic rays using the catalogs of candidate sources. We take into account random deflection in the magnetic fields, with the magnitude of deflection determined by the charge and energy of the cosmic rays, coherence length and magnitude of the extragalactic magnetic field (EGMF), and by distance to source. In addition, in order to compare with the results of TA experiment, we consider the TA exposure. We compare the autocorrelation of the arrival directions corresponding to different source catalogs with the isotropic distribution. We calculate the autocorrelation function for each type of source candidates using this procedure. We will discuss the ability of this method to identify the source type of UHECRs.

10.22323/1.395.0242

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Measurement of the proton-air cross section with Telescope Array’s Black Rock Mesa and Long Ridge fluorescence detectors, and surface array in hybrid mode

Physical review. D/Physical review. D. (2020)

Rasha Abbasi Mitsuru Abe T. Abu‐Zayyad M. Allen R. Azuma

Ultrahigh energy cosmic rays provide the highest known energy source in the Universe to measure proton cross sections. Though conditions for collecting such data are less controlled than an accelerator environment, current generation cosmic ray observatories have large enough exposures to collect significant statistics for a reliable measurement for energies above what can be attained in the laboratory. Cosmic ray measurements of cross section use atmospheric calorimetry to measure depth of air shower maximum (${X}_{\mathrm{max}}$), which is related to the primary particle's energy and mass. The tail of the ${X}_{\mathrm{max}}$ distribution is assumed to be dominated by showers generated by protons, allowing measurement of the inelastic proton-air cross section. In this work, the proton-air inelastic cross section measurement, ${\ensuremath{\sigma}}_{\mathrm{p}\text{-air}}^{\mathrm{inel}}$, using data observed by Telescope Array's Black Rock Mesa and Long Ridge fluorescence detectors and surface detector array in hybrid mode is presented. ${\ensuremath{\sigma}}_{\mathrm{p}\text{-air}}^{\mathrm{inel}}$ is observed to be $520.1\ifmmode\pm\else\textpm\fi{}35.8{[\mathrm{Stat}]}_{\ensuremath{-}42.9}^{+25.3}[\mathrm{Sys}]\text{ }\text{ }\mathrm{mb}$ at $\sqrt{s}=73\text{ }\text{ }\mathrm{TeV}$. The total proton-proton cross section is subsequently inferred from Glauber formalism and is found to be ${\ensuremath{\sigma}}_{\mathrm{pp}}^{\mathrm{tot}}={139.4}_{\ensuremath{-}21.3}^{+23.4}[\mathrm{Stat}{]}_{\ensuremath{-}25.4}^{+15.7}[\mathrm{Sys}]\text{ }\text{ }\mathrm{mb}$.

Air shower

Glauber

10.1103/physrevd.102.062004

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Mass composition of ultrahigh energy cosmic rays from distribution of their arrival directions with the Telescope Array

Physical review. D/Physical review. D. (2024)

Rashid Abbasi Yasuaki Abe T. Abu-Zayyad M. Allen Y. Arai

Mass distribution

Energy distribution

10.1103/physrevd.110.022006

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UHECR mass composition from anisotropy of their arrival directions with the Telescope Array SD

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019) (2021)

M. Kuznetsov P. Tinyakov Rasha Abbasi T. Abu‐Zayyad Monica Allen

We propose a new method for the estimation of ultra-high energy cosmic ray (UHECR) mass composition from a distribution of their arrival directions. The method employs a test statistic (TS) based on a characteristic deflection of UHECR events with respect to the distribution of luminous matter in the local Universe modeled with a flux-weighed 2MRS catalog. Making realistic simulations of the mock UHECR sets, we show that this TS is robust to the presence of galactic and non-extreme extra-galactic magnetic fields and sensitive to the mass composition of events in a set. We apply the method to Telescope Array surface detector data for 11 years and derive new independent constraints on fraction of protons and iron in p-Fe mix at $E > 10$ EeV. At $10 < E < 100$ EeV the data favors increase of allowed proton fraction and decrease of allowed iron fraction, while at $E > 100$ EeV --- pure iron or even more massive composition. This result is in tension with Auger composition model inferred from spectrum-$X_{max}$ fit at $2.7\sigma$ ($2.0\sigma$) for PT'11 (JF'12) regular GMF model.

Mass fraction

10.22323/1.395.0294

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Surface detectors of the TAx4 experiment

arXiv (Cornell University) (2021)

Rasha Abbasi Mitsuru Abe T. Abu-Zayyad M. Allen Yuto Arai

Telescope Array (TA) is the largest ultrahigh energy cosmic-ray (UHECR) observatory in the Northern Hemisphere. It explores the origin of UHECRs by measuring their energy spectrum, arrival-direction distribution, and mass composition using a surface detector (SD) array covering approximately 700 km$^2$ and fluorescence detector (FD) stations. TA has found evidence for a cluster of cosmic rays with energies greater than 57 EeV. In order to confirm this evidence with more data, it is necessary to increase the data collection rate.We have begun building an expansion of TA that we call TAx4. In this paper, we explain the motivation, design, technical features, and expected performance of the TAx4 SD. We also present TAx4's current status and examples of the data that have already been collected.

Source

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Effects of Galactic magnetic field on the UHECR anisotropy studies

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019) (2021)

Ryo Higuchi K. Kawata Rasha Abbasi T. Abu‐Zayyad Monica Allen

Telescope Array (TA) and Auger experiments reported anisotropies in the arrival direction of ultra-high-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 $(f_{\rm ani}, \:\theta)$ 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.

Air shower

10.22323/1.395.0358

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Citations (2)