Primary proton flux around the "knee" region deduced from the observation of air showers accompanied by gamma families

The simultaneous observation of -families and accompanied air showers enables us to obtain the primary proton flux around the knee energy region where no direct measurements are available up to now. We operated a hy- brid experiment which consists of emulsion chambers and the Tibet-II air-shower array (AS) at Yangbajing (4,300 m a.s.l., 606 g/cm ) in 1996-1999. The total area of emulsion chamber (EC) and burst detector (BD) complex was 80 m and they were set up near the center of the Tibet-II air-shower array. We already published the primary proton flux in the energy region ranging from eV to eV using the BD and AS data. We used an artificial neural network to select the proton-induced events from the EC data set. The proton fluxes obtained from this experiment are presented in the knee energy region. Our result suggests that the primary becomes heavy dominant in the knee energy region.