Measurement of the Cosmic Ray Energy Spectrum above 4TeV Using Two Cherenkov Telescopes at YBJ in Tibet

Two air shower Cherenkov telescopes, as prototype detector of a wide field of view (FOV) Cerenkov/fluorescence telescope array (WFCA), are operated at the ARGO-YBJ experiment site in Tibet. Using the Cherenkov signal in the shower images recorded by the Cherenkov telescopes and shower geometry measured by the ARGO-YBJ detector, shower energy can be reconstructed. With the help of such Coincident events an absolute calibration of the energy scale for the ground based experiment will be established by comparing with the balloon borne experimental results.