Increase in the absorption length of inclined extensive air showers

Abstract

The dependence of the number of extensive air showers (EAS) on the zenith angle ϑ is obtained in groups with a constant solid-angle step with different selection types at separations between stations of 500 and 1000 m by using the Yakutsk EAS array data. A bend point is formed at the zenith angle ∼50°. This point shifts with the increasing energy in the direction corresponding to the shift of the cascade-curve maximum depth with the variation of energy. The boundaries of change of these dependences obtained separately at the distances between stations of 500 and 1000 m are different that may be caused by the uncertainty of the lateral distribution function (LDF) used. Thereby, energies of showers detected by the stations with a different separation are not joined.In [1] the presence of bent point depending on the number of extensive air showers (EAS) with E 0 >10 18 eV on a zenith angle ϑ is shown. At first, as a zenith angle ϑ increases, the number of showers decreases or remains constant and then after reaching ∼50° a considerable rise of them begins. The relation between a bend point and a boundary of change of charged particle absorption lengths at a distance of 600 m is also shown. With a rise of zenith angle the transition from the predominance of electron-photon shower component with a short absorption length to the mainly muon component with a weak absorption takes place.At the Yakutsk EAS array the ground-based stations are located in the form of grid consisting of equilateral triangles with sides of 500 m -a small "master" and 1000 m -a large "master". Showers are registered by the array when signals from three stations forming a master triangle coincide. In present paper the dependence for different selection types of showers, as well as for showers registered separately by large and small "masters" are analysed.Showers have been divided into groups with a constant step in cosϑ which corresponds to a constant solid angle [1]. The charged particle absorption length at a distance of 600 m from the axis λ 600 and the energy have been calculated by formulae accepted at the Yakutsk array [2,3]. Showers with axes located within the array perimeter have been selected. Fig.1 presents two types of dependences of the number of showers in groups on a zenith angle ϑ at different energies for a small "master" by the following selection criterions: 1) with densities > 0.8 particles/m 2 and 2) with densities > 2.0 particles/m 2 at each of three stations forming a "master" triangle. A step for cosϑ has been taken as 0.025. On the plot a bend point in dependences at ∼50°, its shift with the energy is seen. There is a restriction in large zenith angles for treated showers which had been changed during different years. In this case a bend point doesn't depend on a density at "master" stations, by which the showers have been selected.

Charm in cosmic rays (The long-flying component of EAS cores)

“…There exist some other observations which could favour this interpretation. First, there is a strong excess [40,41] of showers with energies above 10 18 eV at large zenith angles (> 60 o ). Second, experiments at Pierre Auger Observatory Surface Array revealed that "a significant number of very horizontal events are detected, offering a novel view of EAS" [42].…”

Increase in the absorption length of inclined extensive air showers

“…In [1] the presence of bent point depending on the number of extensive air showers (EAS) with E 0 >10 18 eV on a zenith angle ϑ is shown. At first, as a zenith angle ϑ increases, the number of showers decreases or remains constant and then after reaching ∼50° a considerable rise of them begins.…”

“…Showers have been divided into groups with a constant step in cosϑ which corresponds to a constant solid angle [1]. The charged particle absorption length at a distance of 600 m from the axis λ 600 and the energy have been calculated by formulae accepted at the Yakutsk array [2,3].…”