Muon `Depth -- Intensity' Relation Measured by LVD Underground Experiment and Cosmic-Ray Muon Spectrum at Sea Level

TL;DR

This paper measures the muon depth-intensity relation using the LVD detector, deriving the primary cosmic-ray spectrum index and comparing the underground muon data with sea level measurements.

Contribution

It provides new measurements of the muon depth-intensity relation and the primary cosmic-ray spectrum index based on extensive underground data.

Findings

Derived the primary cosmic-ray spectrum index as 2.78 ± 0.05.

Measured muon intensity distribution from 3 to 12 km w.e. depth.

Presented the sea level muon spectrum based on underground data.

Abstract

We present the analysis of the muon events with all muon multiplicities collected during 21804 hours of operation of the first LVD tower. The measured angular distribution of muon intensity has been converted to the `depth -- vertical intensity' relation in the depth range from 3 to 12 km w.e.. The analysis of this relation allowed to derive the power index, $\gamma$, of the primary all-nucleon spectrum: $\gamma=2.78 \pm 0.05$. The `depth -- vertical intensity' relation has been converted to standard rock and the comparison with the data of other experiments has been done. We present also the derived vertical muon spectrum at sea level.