The High Energy Cosmic Ray Spectrum

摘要

The high-energy all-particle spectrum of cosmic rays follows a power-law like behavior (∞ E γ, γ ≈ -2.7) with features known as " knee" a t 3-5 10~(15) eV (with steepening the spectrum: γ ≈ -3.0) and the ankle at 4 -10 · 10~(18) eV (with again flattening the spectrum). The KASCADE experiment has shown that the knee is due a distinct decrease of the flux of primaries with light mass (Z<6). Assuming that the knee is related to a break in the spectrum of the primary hydrogen nuclei (consequence of a rigidity dependence), a knee like structure in the spectrum of the heavy component (Z > 13) of primary cosmic rays is expected in the energy range of 4 · 10~(16) to 1.2 · 10~(17) eV. We report about the experimental discovery of such a feature in the energy region, transitional from galactic to extragalactic cosmic rays, observed by the KASCADE - Grande experiment, set up in Forschungszentrum Karlsruhe (Germany).