The energy-spectrum of light primaries in the range from 10^{16.6} to 10^{18.2} eV

TL;DR

This study analyzes the energy spectrum of light primary cosmic rays between 10^{16.6} and 10^{18.2} eV, revealing a spectral hardening (ankle) at around 10^{17.08} eV using enhanced data and analysis techniques.

Contribution

It provides new evidence for a spectral ankle in the light cosmic ray component with improved statistics and selection criteria compared to previous studies.

Findings

Evidence for a spectral hardening (ankle) at 10^{17.08} eV.

Spectrum compatible with single or broken power-law models.

Enhanced data set improves statistical significance of the spectral feature.

Abstract

Data of the Grande extension of the KASCADE experiment allows us to study extensive air showers induced by primary cosmic rays with energies above 10^{16} eV. The energy of an event is estimated in terms of the number of charged particles (Nch ) and the number of muons (N{\mu} ) measured at an altitude of 110 m a.s.l. While a combination of the two numbers is used for the energy, the ratio defines the primary mass (group). The spectrum of the combined light and medium mass components, recently measured with KASCADE-Grande, was found to be compatible with both a single power-law and a broken power-law in the energy range between 10^{16.3} and 10^{18} eV. In this contribution we will present the investigation of possible structures in the spectrum of light primaries with increased statistics both from a larger data set including more recent measurements and by using a larger fiducial area than in the previous study. With the better statistical accuracy and with optimized selection criteria for enhancing light primaries we have found evidence for a hardening (ankle) of the spectrum of the light component at an energy of 10^{17.08+-0.08} eV.