The Knee of the Cosmic Hydrogen and Helium Spectrum below 1 PeV Measured by ARGO-YBJ and a Cherenkov Telescope of LHAASO

TL;DR

This paper reports the first measurement of the combined Hydrogen and Helium cosmic ray spectrum knee at around 640 TeV using ARGO-YBJ and LHAASO, providing key insights into cosmic ray origins.

Contribution

It presents the first combined measurement of Hydrogen and Helium spectra identifying the knee feature at 640 TeV, advancing cosmic ray spectral studies.

Findings

Knee observed at 640+/-87 TeV in Hydrogen and Helium spectrum

Spectrum shows a clear steepening at the knee

Provides new data for cosmic ray acceleration models

Abstract

The measurement of cosmic ray energy spectra, in particular for individual species, is an essential approach in finding their origin. Locating the "knees" of the spectra is an important part of the approach and has yet to be achieved. Here we report a measurement of the mixed Hydrogen and Helium spectrum using the combination of the ARGO-YBJ experiment and of a prototype Cherenkov telescope for the LHAASO experiment. A knee feature at 640+/-87 TeV, with a clear steepening of the spectrum, is observed. This gives fundamental inputs to galactic cosmic ray acceleration models.