Observation of a spectral hardening in cosmic ray boron spectrum with the DAMPE space mission

TL;DR

This paper reports the first direct measurement of the cosmic ray boron spectrum up to 8 TeV/n, revealing a spectral hardening at around 182 GeV/n, which provides new insights into cosmic ray propagation mechanisms.

Contribution

The study presents the first direct measurement of the boron spectrum up to 8 TeV/n, showing a spectral hardening that enhances understanding of cosmic ray propagation.

Findings

Spectral hardening observed at 182 GeV/n

Boron spectrum hardening is roughly twice that of primary cosmic rays

Disfavored simple power law model at 8σ confidence level

Abstract

Secondary cosmic ray fluxes are important probes of the propagation and interaction of high-energy particles in the Galaxy. Recent measurements of primary and secondary cosmic ray nuclei have revealed unexpected spectral features that demand a deeper understanding. In this work we report the direct measurement of the cosmic ray boron spectrum from 10 GeV/n to 8 TeV/n with eight years of data collected by the Dark Matter Particle Explorer (DAMPE) mission. The measured spectrum shows an evident hardening at $182\pm24$ GeV/n with a spectral power index of $\gamma_1 = 3.02 \pm 0.01$ before the break and an index change of $\Delta \gamma = 0.31 \pm 0.05$ after the break. A simple power law model is disfavored at a confidence level of 8$\sigma$. Compared with the hardenings measured in the DAMPE proton and helium spectra, the secondary boron spectrum hardens roughly twice as much as these primaries, which is consistent with a propagation related mechanism to interpret the spectral hardenings of cosmic rays observed at hundreds of GeV/n.