Cosmic Ray Energy Spectra and Mass Composition at the Knee – Recent Results from KASCADE –

Abstract

Recent results from the KASCADE experiment on measurements of cosmic rays in the energy range of the knee are presented. Emphasis is placed on energy spectra of individual mass groups as obtained from an twodimensional unfolding applied to the reconstructed electron and truncated muon numbers of each individual EAS. The data show a knee-like structure in the energy spectra of light primaries (p, He, C) and an increasing dominance of heavy ones (A > ∼ 20) towards higher energies. This basic result is robust against uncertainties of the applied interaction models QGSJET and SIBYLL which are used in the shower simulations to analyse the data. Slight differences observed between experimental data and EAS simulations provide important clues for further improvements of the interaction models. The data are complemented by new limits on global anisotropies in the arrival directions of CRs and by upper limits on point sources. Astrophysical implications for discriminating models of maximum acceleration energy vs galactic diffusion/drift models of the knee are discussed based on this data.

Lorentz invariance violation and chemical composition of ultra high energy cosmic rays

“…The maximal energy of galactic CRs being dependent on the charge, we expect the actual end-point to the galactic CR spectrum to be determined by heavy nuclei, with the chemical composition becoming heavier and heavier with increasing energy. Experimental data in the energy range 10 17 eV E 10 18 eV are compatible with this expectation [39]. At energy E 10 18 eV, however, the chemical composition becomes again very light, being compatible with the presence of just protons [40,41].…”

THE FERMI BUBBLE AS A SOURCE OF COSMIC RAYS IN THE ENERGY RANGE >1015eV

“…The spectrum has been multiplied by E 2 for clarity. Experiments include Tibet AS-γ (Amenomori et al 2008), KASCADE (Kampert et al 2004), KASCADE-Grande (Apel et al 2009), High Resolution Fly's Eye cosmic-ray detector-I (HiRes-I; Abbasi et al 2009), HiRes-II (Abbasi et al 2008), and Auger (Abraham et al 2010). The solid line shows the contribution from the bubble predicted by Equation 34for E 1 = 10 15 eV < E < E 2 = 10 19 eV.…”

Lorentz invariance violation and chemical composition of ultra-high energy cosmic rays

“…Experimental data in the energy range 10 17 eV E 10 18 eV are compatible with this expectation [39]. At energy E 10 18 eV, however, the chemical composition becomes again very light, being compatible with the presence of just protons [40,41].…”