  Cosmic rays are important probe of a number of fundamental physical problems
such as the acceleration of high and very high energy particles in extreme
astrophysical environments. The Galactic center is widely anticipated to be an
important cosmic-ray source and the observations of some Imaging Atmospheric
Cherenkov Telescopes did successfully reveal a component of TeV-PeV cosmic rays
in the vicinity of the Galactic center. Here we report the identification of
GeV-TeV cosmic rays in the central molecular zone with the $\gamma$-ray
observations of the Fermi Large Area Telescope, whose spectrum and spatial
gradient are consistent with that measured by the Imaging Atmospheric Cherenkov
Telescopes but the corresponding cosmic-ray energy density is substantially
lower than the so-called cosmic-ray sea component, suggesting the presence of a
high energy particle accelerator at the Galactic center and the existence of a
barrier that can effectively suppress the penetration of the particles from the
cosmic-ray sea to the central molecular zone.
