EAS electron and muon distributions and size spectra from the GAMMA installation

Abstract

The phenomenological characteristics of the electron and muon components of extensive air showers with the range 105⩽Ne⩽107 are obtained from the GAMMA installation of the ANI experiment at Mt Aragats in Armenia at an observation level of 700 g cm-2. The experimental results are compared with other experiments and with the simulation carried out using the CORSIKA code and ARES package.

Rigidity-dependent cosmic ray energy spectra in the knee region obtained with the GAMMA experiment

“…The given trigger condition provides EAS detections with an EAS size threshold N ch > (0.5 − 1) · 10 5 for a location of the EAS core within the R < 50 m circle. The shower size thresholds for 100% shower detection efficiency are equal to N ch = 3 · 10 5 and N ch = 5 · 10 5 for EAS core locations within R < 25 m and R < 50 m respectively [18]. Before being placed on the scintillator casing, all photomultipliers were tested by a test bench using a luminodiode method where the corresponding parameters of the logarithmic ADC and the upper limit ((0.5 − 1) · 10 4 ) [28] of the particle density measurement ranges were determined for each detector.…”

“…• [18]. The reconstruction of the EAS size (N ch ), shower age (s) and core coordinates (x 0 , y 0 ) is performed based on the Nishimura-Kamata-Greisen (NKG) approximation to the measured charged particle densities ({n i }, i = 1, .…”

“…. , 150) in the underground muon hall is carried out by restricting the distance to R µ < 50 m from the shower core (the so-called EAS "truncated" muon size [18,33]) and using the approximation to the muon lateral distribution function [18,34]: ρ µ (r) = cN µ (R µ < 50m) exp (−r/r 0 )/(r/r 0 ) 0.7 , where r 0 = 80 m [35] and c = 1/2π 50 0 ρ(r)rdr. The EAS truncated muon size N µ (R µ < 50m) is estimated at known (from the EAS surface array) shower core coordinates in the underground muon hall.…”

“…A ∼ 5% agreement between the EGS (including the EAS γ-quanta contribu- tion) and NKG simulated EAS data was attained for an E e ≃ 1 MeV kinetic energy threshold of shower electrons (and positrons) in the NKG mode, considering only the 7m < R i < 80m ring area used in the determination of the shower age parameter. Thus the underestimation of the EAS particle density due to the threshold of the detected energy deposit (E d ≃ 8 MeV [18,25]) in the scintillators is compensated by the EAS γ-quanta contribution. The corresponding biases…”

“…The GAMMA facility (Fig. 1) was designed at the beginning of the 1990's in the framework of the ANI experiment [17] and the first results of EAS investigations were presented in [18][19][20][21]. The main characteristic features of the GAMMA experiment are the mountain location, the symmetric location of the EAS detectors, and the underground muon scintillation carpet which detects the EAS muon component with energy E µ > 5 GeV.…”