The Galactic Center: A PeV Cosmic Ray Acceleration Factory

In this work, we propose that the cosmic rays are accelerated up to >PeV in galactic center. The interaction between cosmic rays and molecular clouds is responsible for the multi-TeV gamma-ray emissions for both the point source and diffuse one today. Enhanced by the small volume filling factor of the clumpy structure, the absorption of the gamma-rays leads to a sharp cut-off spectrum at tens of TeV produced in galactic center. Away from GC, the volume filling factor grows up and the absorption enhancement becomes ignorable and pristine gamma-ray spectrum is preserved. As a result, the spectra of gamma-ray emissions for both point source and diffuse one can be successfully reproduced under such self-consistent picture. In addition, the spectrum from the point source of galactic center is expected to exhibit a "survived-tail" at ~100 TeV, where the absorption cross section starts to decrease. Such a feature distinguishes the absorption model from acceleration model and will be tested by future projects, such as CTA, LHAASO. Neutrinos are simultaneously produced as the gamma-rays during PP-collision. With 5~10 yrs observations, the IceCube and KM3Net experiments will be able to detect the PeV source according to our calculation.