The energy spectrum of all-particle cosmic rays around the knee region observed with the Tibet-III air-shower array

TL;DR

This study updates the measurement of the all-particle cosmic ray energy spectrum around the knee region using data from the Tibet-III array, confirming a spectral break at approximately 4 PeV with detailed spectral indices.

Contribution

It provides an extended and refined measurement of the cosmic ray spectrum around the knee, with improved data analysis over a wider energy range from 2000 to 2004.

Findings

Knee position identified at around 4 PeV.

Spectral index below 1 PeV is -2.68 ± 0.02.

Spectral index above 4 PeV is -3.12 ± 0.01.

Abstract

We have already reported the first result on the all-particle spectrum around the knee region based on data from 2000 November to 2001 October observed by the Tibet-III air-shower array. In this paper, we present an updated result using data set collected in the period from 2000 November through 2004 October in a wide range over 3 decades between $10^{14}$ eV and $10^{17}$ eV, in which the position of the knee is clearly seen at around 4 PeV. The spectral index is -2.68 $\pm$ 0.02(stat.) below 1PeV, while it is -3.12 $\pm$ 0.01(stat.) above 4 PeV in the case of QGSJET+HD model, and various systematic errors are under study now.