Speaker
JIN Chao
Description
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.
Primary authors
JIN Chao
Wei Liu
(Key Laboratory of Particle Astrophysics, Institute of High Energy Physics)
Yi Qing Guo
(Key Laboratory of Particle Astrophysics, Institute of High Energy Physics)
Mr
hongbo HU Hongbo
(IHEP)
