Study of themuon content of high-energy air showers with KASCADE-Grande

In this work, we report measurements on the muon content (Eth > 230 MeV) of extensive air showers (EAS) induced by cosmic rays with primary energy from 10 PeV up to 1 EeV performed with the KASCADE-Grande experiment. The measurements are confronted with SIBYLL 2.3. The results are focused on the dependence of the total muon number and the lateral density distribution of muons in EAS on the zenith angle and the total number of charged particles in the shower. We also present updated results of a detailed study of the attenuation length of shower muons, which reveal a deviation between the measured data and the predictions of the post-LHC hadronic interaction models SIBYLL 2.3, QGSJET-II-04 and EPOS-LHC.

Tests of the SIBYLL 2.3 high-energy hadronic interaction model using the KASCADE-Grande muon data

The KASCADE-Grande observatory was a ground-based air shower array dedicated to study the energy and composition of cosmic rays in the energy interval E = 1 PeV –1 EeV. The experiment consisted of different detector systems which allowed the simultaneous measurement of distinct components of air showers (EAS), such as the muon content. In this contribution, we study the total muon number and the lateral density distribution of muons in EAS detected by KASCADE-Grande as a function of the zenith angle and the total number of charged particles. The attenuation length of the muon content of EAS is also measured. The results are compared with the predictions of the SIBYLL 2.3 high-energy hadronic interaction model.

Study of extensive air showers at Mount Norikura. I. Measurement of lateral structure

The lateral density distribution of charged particles in EAS is one of the essential parameters for the analysis of individual EAS. To measure the lateral density distribution in detail, 100 ¼-m2 scintillators were arranged in a lattice configuration with a unit distance of 5 m or 2.5 m. The conventional EAS array of 20 scintillators was also used to obtain densities up to about 100 m from the center. These observations are much more accurate than those obtained previously, and it has been found that there are various types of structure functions which can be approximated by the functions for single cascades of age parameter from 0.6 to 1.6. It was difficult in some instances to fit the lateral distribution by a unique function, especially for small EAS.The two-dimensional map obtained by means of the above 100 detectors shows that individual EAS have rarely a complicated structure within a range of about 20 m from the axis. The results are discussed in relation to the character of high-energy interactions as well as to fluctuations in the development of EAS.

Study of extensive air showers at Mount Norikura. IV. Lateral distribution of muons for types of EAS

Muons accompanied by EAS have been observed by a neon hodoscope array 6 m2 in area placed 36 m from the center of the EAS array. The lateral density distribution function of muons and an average density at fixed distance are studied with respect to the size and age parameter of EAS. The EAS are in a size range of 106 to 107, and the muon density at distances of 15–55 m from the axis of EAS has been observed for muons which penetrate 20 cm of lead.Preliminary results obtained in this experiment are as follows: (1) The lateral density distribution of muons shows clear correlation with that of electrons: assuming the distribution function to be a power function of the distance from the axis, the exponent varies from steeper than −1.5 to flatter than −1.0 for younger and older EAS respectively. (2) The size dependence of muon density can be expressed as [Formula: see text], and is independent of the age parameter of EAS.

Study of extensive air showers at Mount Norikura. III. Core structure and high-energy events

An area of 3 × 4 m2 is covered by 48 plastic scintillators above and below a water tank 2 m in depth. From maps of the charged-particle density and the energy-flow density in the core region, properties of EAS cores and of the high-energy nucleon component have been studied. About 25% of observed cores show the complicated structure of a "multiple core". These can be understood as due to effects of high-energy nuclear particles having large transverse momenta of several GeV/c to a few tens of GeV/c. The frequency of occurrence of such events increases with the size of EAS only slowly, but it decreases rapidly with increasing distance between the main cores and subcores. There is no clear distinction in the average lateral density distribution of charged particles between these multiple-core EAS and ordinary EAS at points distant from the cores.Comparing the particle density in both layers of detectors (top and bottom), the activity of cores has been studied. This fluctuates more than would be expected from the lateral structure of the showers.