Lateral Distribution for Aligned Events in Muon Groups Deep Underground

TL;DR

This study analyzes the lateral distribution of muons in underground cosmic ray events, finding that the separation distribution follows an exponential law and becomes steeper at higher energies, with no difference between aligned and all groups.

Contribution

It provides the first detailed analysis of muon separation distributions in aligned cosmic ray events deep underground, revealing energy-dependent steepening without differences between aligned and general groups.

Findings

Separation distribution follows an exponential law.

Distribution steepens with increasing energy.

No difference between aligned and all muon groups.

Abstract

The paper concerns the so-called aligned events observed in cosmic rays. The phenomenon of the alignment of the most energetic subcores of gamma-ray--hadron ($\gamma-h$) families (particles of the highest energies in the central EAS core) was firstly found in the "Pamir" emulsion chamber experiment and related to a coplanar particle production at $E_0>10^{16}$ eV. Here a separation distribution (distances between pairs of muons) for aligned events has been analyzed throughout muon groups measured by Baksan Underground Scintillation Telescope (BUST) for threshold energies $0.85 \div 3.2$ TeV during a period of 7.7 years. Only muon groups of multiplicity $m\geq 4$ with inclined trajectories for an interval of zenith angles $50^\circ - 60^\circ$ were selected for the analysis. The analysis has revealed that the distribution complies with the exponential law. Meanwhile the distributions become steeper with the increase of threshold energy. There has been no difference between the lateral distribution of all the groups and the distribution of the aligned groups.