The rise of muon content in extensive air showers after the 3 PeV knee of the primary cosmic ray spectrum according to data of the Tien Shan mountain installation

TL;DR

This study compiles experimental data on muon content in extensive air showers at Tien Shan, revealing an unexpected increase in muons above the 3 PeV knee, challenging existing hadronic interaction models.

Contribution

It provides a comprehensive comparison of muon measurements using different techniques, highlighting discrepancies with current models of cosmic ray interactions.

Findings

Muon excess observed above the 3 PeV knee

Experimental results agree across different detection methods

Contradicts predictions of standard hadron interaction models

Abstract

We put together the experimental results on muon component of extensive air showers (EAS) which were gained with various techniques at the detector complex of the Tien Shan mountain station. According to this comparison, the problem of the EAS muon content in the range of primary cosmic ray energies (1-100)PeV seems to be more complicated than it was usually supposed. Generally, from the models of nuclear interaction it follows that the EAS which have produced gamma-hadron families in the Tien Shan X-ray emulsion chamber did preferably originate from interaction of the light cosmic ray nuclei, such that their muon abundance must be ~1.5 times below an average calculated over all showers. In contrary, the experimental muon counts in the EAS with families demonstrate a (1.5-2)-fold excess above the average, and this difference starts to be observable in the showers with the energy above the 3PeV knee of the primary cosmic ray spectrum. Later on, the rise of muon production in EAS after the knee was confirmed at Tien Shan by another experiment on detection of the neutrons stemmed from interaction of cosmic ray muons. Thus, the results obtained by the two completely different methods do mutually agree with each other but contradict to the common models of hadron interaction.