Energy Spectrum of Ultrahigh-Energy Cosmic Rays according to Data from the Ground-Based Scintillation Detectors of the Y
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, PARTICLES, FIELDS, GRAVITATION, AND ASTROPHYSICS
Energy Spectrum of Ultrahigh-Energy Cosmic Rays according to Data from the Ground-Based Scintillation Detectors of the Yakutsk EAS Array A. V. Glushkova,*, M. I. Pravdina, and A. V. Saburova aShafer
Institute of Cosmophysical Research and Aeronomy, Yakutsk Research Center, Siberian Branch, Russian Academy of Sciences, pr. Lenina 31, Yakutsk, 677980 Russia *e-mail: [email protected] Received November 12, 2017; revised October 3, 2018; accepted October 18, 2018
Abstract—The energy spectrum of cosmic rays with energies E0 ≥ 1017 eV over the period of continuous observations in 1974–2017 is analyzed. A refined formula for estimating the primary particle energy is used for individual events. It is derived from our calculations of the responses of the ground-based and underground scintillation detectors of the Yakutsk extensive air shower array within the QGSjet-01-d, QGSjet-II-04, SIBYLL-2.1, and EPOS-LHC models by applying the CORSIKA package. The new estimate of E0 is appreciably lower than its previously used value. DOI: 10.1134/S1063776119020195
1. INTRODUCTION The energy spectrum of ultrahigh-energy (E0 ≥ 1017 eV) cosmic rays (CRs) is one of the key links in the chain of complex problems of understanding the nature of primary particles with such energies. The experimental results obtained at various extensive air shower (EAS) arrays [1–7] differ between themselves in absolute intensity by almost a factor of 2, but are close in form [8]. This situation is largely explained by the fact that most of the biggest world arrays use different methods for determining the primary particle energy E0 in view of different EAS detection techniques. Here one cannot do without theoretical ideas of EAS development. The Yakutsk EAS array is the oldest in the world. It is located near Yakutsk at an altitude of 100 m above sea level (1020 g cm–2). The first results at a prototype of 13 stations were obtained in 1970 [9]. The continuous detection of EASs was begun in 1973 [10–12]. At that time 35 stations involved in the selection of showers occupied an area of more than 17 km2. The stations were arranged so that they formed a grid of triangles with a side of 1000 m over the entire area and 500 m in its central part, which was 0.7 and 2.6 km2 before and after 1985, respectively. During the reconstruction in 1990–1992 the total area over which the stations were arranged decreased, but their number increased by almost a factor of 1.5. At present, 49 stations are arranged over an area of 8 km2, forming a uniform grid of triangles with a side of 500 m (Fig. 1). This allows one to investigate CRs in the range 2 × 1017–3 ×
1019 eV with homogeneous event selection conditions over the entire area. Two scintillation detectors with an area of 2 m2 each are installed at each station. Ten more such detectors that are not involved in the selection of events are installed at the array center in a circle with a radius of 250 m (Fig. 2). The Yakutsk EAS array stands out among the other bigg
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