A Halo Event observed by the Hybrid Experiment at Mt. Chacaltaya

An experiment using an air shower array, a hadron calorimeter and an emulsion chamber is under way at Mt. Chacaltaya (5200 m, Bolivia). One of the highest energy events, having a halo (∼ 1 cm) in the centre of the family together with many γ-ray and hadron showers, is analyzed in detail.Available data for the event are on the halo (Ehalo=750 TeV) and on the high energy particles of electron/photon components by the emulsion chamber, and on the characteristics of the accompanied air shower (Ne=7.0×107, s=0.59) by the air shower array.The diagram of the air shower size and the total energy of electron/photon components in the family, which shows discrepancy between the experimental data and simulated events (QGSJET code for nuclear collisions) in our previous reports, is discussed including the present event.