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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Citations (27)

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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Development of Fuel Cell Production System Contributes to Higher Productivity and Lower Costs

Journal of the Society of Powder Technology Japan (2022)

Daichi Irishika Yoshinori Takagi

We have focused on fuel cells as new clean energy to improve humanity’s future. In recent years, with the prospect of widespread use of fuel cells, it is required to establish new technologies for reducing to manufacturing process time and costs. In 2013, we began to research technologies for the mass production of MEA, with assistance from the New Energy and Industrial Technology Development Organization, which is a key component of polymer electrolyte fuel cells. In 2016, we completed development and shipped the world’s first direct coating CCM mass production equipment. We will continue to expand its business in this area, with a view to driving the growth of the overall fuel cell field and contributing to the realization of a sustainable hydrogen economy.

10.4164/sptj.59.570

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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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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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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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LiteBIRD: a small satellite for the study of B-mode polarization and inflation from cosmic background radiation detection

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2012)

M. Hazumi J. Borrill Y. Chinone M. Dobbs H. Fuke

LiteBIRD [Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection] is a small satellite to map the polarization of the cosmic microwave background (CMB) radiation over the full sky at large angular scales with unprecedented precision. Cosmological inflation, which is the leading hypothesis to resolve the problems in the Big Bang theory, predicts that primordial gravitational waves were created during the inflationary era. Measurements of polarization of the CMB radiation are known as the best probe to detect the primordial gravitational waves. The LiteBIRD working group is authorized by the Japanese Steering Committee for Space Science (SCSS) and is supported by JAXA. It has more than 50 members from Japan, USA and Canada. The scientific objective of LiteBIRD is to test all the representative inflation models that satisfy single-field slow-roll conditions and lie in the large-field regime. To this end, the requirement on the precision of the tensor-to-scalar ratio, r, at LiteBIRD is equal to or less than 0.001. Our baseline design adopts an array of multi-chroic superconducting polarimeters that are read out with high multiplexing factors in the frequency domain for a compact focal plane. The required sensitivity of 1.8μKarcmin is achieved with 2000 TES bolometers at 100mK. The cryogenic system is based on the Stirling/JT technology developed for SPICA, and the continuous ADR system shares the design with future X-ray satellites.

Mode (computer interface)

Cosmic background radiation

10.1117/12.926743

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Citations (70)

First Time‐Resolved Leader Spectra Associated With a Downward Terrestrial Gamma‐Ray Flash Detected at the Telescope Array Surface Detector

Journal of Geophysical Research Atmospheres (2024)

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

Abstract Optical emissions associated with Terrestrial Gamma ray Flashes (TGFs) have recently become important subjects in space‐based and ground‐based observations as they can help us understand how TGFs are produced during thunderstorms. In this paper, we present the first time‐resolved leader spectra of the optical component associated with a downward TGF. The TGF was observed by the Telescope Array Surface Detector (TASD) simultaneously with other lightning detectors, including a Lightning Mapping Array (LMA), an INTerFerometer (INTF), a Fast Antenna (FA), and a spectroscopic system. The spectroscopic system recorded leader spectra at 29,900 frames per second (33.44 s time resolution), covering a spectral range from 400 to 900 nm, with 2.1 nm per pixel. The recordings of the leader spectra began 11.7 ms before the kA return stroke and at a height of 2.37 km above the ground. These spectra reveal that optical emissions of singly ionized nitrogen and oxygen occur between 167 s before and 267 s after the TGF detection, while optical emissions of neutrals (H I, 656 nm; N I, 744 nm, and O I, 777 nm) occur right at the moment of the detection. The time‐dependent spectra reveal differences in the optical emissions of lightning leaders with and without downward TGFs.

10.1029/2024jd041720

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The status of the TALE surface detector array and TALE infill project

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

S. Ogio Rasha Abbasi T. Abu‐Zayyad Monica Allen Yuto Arai

Routine hybrid observations of the surface detectors (SD) in conjunction with the fluorescence detectors (FD) of the Telescope Array Low-energy Extension (TALE) began in November 2018. In this presentation, we will describe the simulation studies of detector aperture and resolution of the TALE SD, and report on the latest observation results other than the energy spectrum. We are also in the process of expanding the experiment by 50 SDs, with even smaller nearest-neighbor spacing, in order lower the energy threshold to match that of the Cherenkov-dominated events seen by the FD. Details of the upgrade and expected performance of this new extension will be discussed.

Upgrade

Aperture (computer memory)

10.22323/1.395.0255

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Citations (1)