Klein–Nishina Effect and the Cosmic Ray Electron Spectrum
Kun Fang1, Xiao-Jun Bi1,2*, Su-Jie Lin3, and Qiang Yuan4,5,6*
1Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China 2University of Chinese Academy of Sciences, Beijing 100049, China 3School of Physics and Astronomy, Sun Yat-Sen University, Zhuhai 519082, China 4Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China 5School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China 6Center for High Energy Physics, Peking University, Beijing 100871, China
Abstract：Radiative energy losses are very important in regulating the cosmic ray electron and/or positron (CRE) spectrum during their propagation in the Milky Way. Particularly, the Klein–Nishina (KN) effect of the inverse Compton scattering (ICS) results in less efficient energy losses of high-energy electrons, which is expected to leave imprints on the propagated electron spectrum. It has been proposed that the hardening of CRE spectra around 50 GeV observed by Fermi-LAT, AMS-02, and DAMPE could be due to the KN effect. We show in this work that the transition from the Thomson regime to the KN regime of the ICS is actually quite smooth compared with the approximate treatment adopted in some previous works. As a result, the observed spectral hardening of CREs cannot be explained by the KN effect. It means that an additional hardening of the primary electrons spectrum is needed. We also provide a parameterized form for the accurate calculation of the ICS energy-loss rate in a wide energy range.
. [J]. 中国物理快报, 2021, 38(3): 39801-039801.
Kun Fang, Xiao-Jun Bi, Su-Jie Lin, and Qiang Yuan. Klein–Nishina Effect and the Cosmic Ray Electron Spectrum. Chin. Phys. Lett., 2021, 38(3): 39801-039801.
2021, Vol. 38 
