Ankle-like Feature in the Energy Spectrum of Light Elements of Cosmic Rays Observed with KASCADE-Grande

TL;DR

This study reports an updated analysis of cosmic ray spectra, revealing a spectral hardening in light elements at around 10^17.08 eV, based on enhanced data and optimized selection criteria from the KASCADE-Grande experiment.

Contribution

The paper introduces an improved analysis with increased statistics and refined selection methods, identifying a new spectral feature in light cosmic ray components.

Findings

Detection of a spectral hardening at 10^17.08 eV in light elements

Change in power law index from -3.25 to -2.79

Enhanced data set and selection criteria used

Abstract

Recent results of the KASCADE-Grande experiment provided evidence for a mild knee-like structure in the all-particle spectrum of cosmic rays at $E = 10^{16.92 \pm 0.10} \, \mathrm{eV}$, which was found to be due to a steepening in the flux of heavy primary particles. The spectrum of the combined components of light and intermediate masses was found to be compatible with a single power law in the energy range from $10^{16.3} \, \mathrm{eV}$ to $10^{18} \, \mathrm{eV}$. In this paper, we present an update of this analysis by using data with increased statistics, originating both from a larger data set including more recent measurements and by using a larger fiducial area. In addition, optimized selection criteria for enhancing light primaries are applied. We find a spectral feature for light elements, namely a hardening at $E = 10^{17.08 \pm 0.08} \, \mathrm{eV}$ with a change of the power law index from $-3.25 \pm 0.05$ to $-2.79 \pm 0.08$.