Second China LHC Physics Workshop (CLHCP 2016): 第2届中国LHC物理工作会议

The origin of the cosmic-ray knee has remained a puzzle since its discovery over 60 years. In addition, Some latest experiments have revealed a spectral cutoff of the electron around 1 TeV. We find these two spectral breaks have a similar Lorentz factor $\sim 10^6$, and interpret this similarity with a threshold interaction. Considering the lack of photons of 1 eV in the Galaxy which may produce those breaks through $e^+ + e^-$ pair production process, we postulate the existing of a new particle X abundant in the Galaxy. The interaction process $CR \ + \ X \ \longrightarrow \ CR \ + \ X^{\prime}$ can take place when the effective energy is sufficient to convert it into the mass of another unknown particle $X^{\prime}$ (as a representative to all possible threshold inelastic interactions), where the mass of $X^{\prime}$ is $10^6$ higher than that of the X with respect to the above mentioned common Lorentz factor. Thus cosmic rays will loss their energy above the threshold and produce a spectral break. Under this scenario, we can reproduce the spectral break for both the nuclei and electron, and predict a flattened spectrum for electrons after the cutoff. Given that there are uncertainties of experiments in determining the actual spectra of these breaks and their components, our model allows a wide mass range of the particle X from ultra low value to around 1 eV.