Dark Matter Particle Explorer
Science & Technology

Dark Matter Particle Explorer Has Measured High-Precision Galactic Cosmic Ray Energy Spectrum

Dark Matter Particle Explorer. Credit score: DAMPE Collaboration

Dark Matter Particle Explorer (DAMPE) Collaboration immediately noticed a spectral softening of helium nuclei at about 34TeV for the primary time. This work was based mostly on measurements information of the helium spectrum with kinetic energies from 70 GeV to 80 TeV (17.5 GeV/n to twenty TeV/n for per nucleon) recorded by the DAMPE.

The related outcomes had been printed in Bodily Overview Letters.

Galactic cosmic rays (GCRs) presents necessary methods to deeply perceive the astrophysical particle origin and accelerators and the interstellar medium of the Galaxy. Helium nuclei, the second most plentiful nuclear aspect of cosmic rays, is a distinguishing function of area.

As for GCRs, the vitality spectrum is meant to observe a destructive energy regulation distribution when energies are under the “knee” (at 3-4 PeV). Nonetheless, current experiments noticed a hardening of the spectrum at kinetic vitality of a number of hundred GeV/n, indicating potential new sources and acceleration mechanism of GCRs.

On this research, the GCR helium spectrum from 70 GeV to 80 TeV was measured utilizing 4.5 years of the DAMPE flight information. The utmost measurable rigidity reached by DAMPE improved to 10 instances larger than that detected by the Alpha Magnetic Spectrometer (AMS-02) led by DING Zhaozhong. The outcomes confirmed the hardening function of the helium spectrum, reported beforehand in experiments measured by AMS-02, at round 1.2 TeV given a excessive significance of 24.6σ. Apart from, a softening function was additional revealed at round 34 TeV with a significance of 4.3σ.

DAMPE Collaboration printed the measurement outcomes of cosmic-ray proton spectrum in 2019 (Science Advances) and noticed modifications of the spectral index at about 14 TeV. In contrast with the DAMPE proton spectrum, The DAMPE helium nuclei spectrum confirmed related pattern, which suggests the modifications of power-law spectral indices γ could also be depending on particle cost, although a mass-dependent softening couldn’t be excluded restricted by present information.

On this work, the workforce led by Prof. HUANG Guangshun and Prof. ZHANG Yunlong from the State Key Laboratory of Particle Detection and Electronics of the College of Science and Know-how of China (USTC) first recognized the quenching impact of BGO crystals on relativistic heavy ions by investigating the ionization vitality response of BGO calorimeter to ions. Prof. WEI Yifeng quantified quenching elements of ions with completely different energies. This work effectively helped the reconstruction of helium vitality spectrum.

BGO calorimeter, the principle sub-detector for vitality measurement of DAMPE, was designed by the workforce led by Prof. AN Qi and Prof. LIU Shubin from USTC. It covers wider vary of energies, and has higher vitality decision and particle discrimination means than different on-orbit detectors.

These outcomes counsel the existence of an accelerator for cosmic rays close to earth producing protons and helium nuclei, and the softening vitality is said to its higher restrict worth, which extends our understanding of GCR sources and acceleration mechanisms.

Reference: “Measurement of the Cosmic Ray Helium Energy Spectrum from 70 GeV to 80 TeV with the DAMPE House Mission” by F. Alemanno et al. (DAMPE Collaboration), 18 Could 2021, Bodily Overview Letters.
DOI: 10.1103/PhysRevLett.126.201102

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