On the PeV knee of cosmic rays spectrum and TeV cutoff of electron spectrum

Abstract

Spectra of Cosmic Rays (CRs), particularly their features, may hold essential information about astroparticle and fundamental physics. Realizing that both $4$ PeV CR knee and electron's TeV break have nearly identical Lorentz factor, i.e. $\gamma \sim 10^6$, we propose that both CR nuclei and electron experience a threshold interaction with unknown light particle $\rm X$, widespread in the diffusive halo. The interaction occurs only when the Lorentz factor of CRs is larger than $10^6$. Via this process, the energy spectrum of each component has deformation above the threshold Lorentz factor, so both knee and spectral break of electrons can be naturally reproduced. Given the large uncertainties of the available measurements and simplified assumption, our model accommodates a wide mass range of the particle X, which is allowable from ultralight value to $\sim 1$ eV.