Abstract
The ARGO-YBJ detector, located at high altitude in the Cosmic Ray Observatory of Yangbajing in Tibet (4300 m asl, about 600 g/cm2 of atmospheric depth) provides the opportunity for the study, with unprecedented resolution, of cosmic ray physics in the primary energy region between 1012 and 1016 eV. Preliminary results of the measurements of the all-particle and light-component (i.e. protons and helium) energy spectra between approximately 5 TeV and 5 PeV are reported and discussed.
Highlights
There is a general consensus that galactic cosmic rays up to the “knee” (∼ 4 PeV, with 1 PeV = 1015 eV) mainly originate in Supernova Remnants (SNRs)
A measurement of the CR primary energy spectrum in the energy range few TeV – 10 PeV is under way with the ARGO-YBJ experiment
The study of the charged particle lateral density function (LDF) at ground is expected to provide information on the longitudinal profile of the showers in the atmosphere, that is to estimate their development stage, or the so-called age, which is related to Xmax, the atmospheric depth at which the cascade reaches its
Summary
In the knee region (and above) the measurements of the CR primary spectrum are carried out by EAS arrays. In this case mass composition studies are extremely difficult and often affected by large systematic uncertainties. The results of the Tibet ASγ and the BASJE experiments, located at 4300 m a.s.l and at 5200 m a.s.l. respectively, do favour a heavier composition because the proton component is no more dominant at the knee [8, 9]. A measurement of the CR primary energy spectrum (all-particle and light-component) in the energy range few TeV – 10 PeV is under way with the ARGO-YBJ experiment (for a description of the detector and a report of the latest physics results see [12]). More details on the results obtained with the “hybrid measurement” are given in [14, 15]
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