抄録
The direct measurement of the attenuation length for an individual EAS through 200 g/cm2 water has been made at Mt. Norikura (2770 m a.s.l.) from 1964 to 1968. The mean value of the observed attenuation length (120±20 g/cm2) in the interval of the size (106>N≥105) is less than the values which were estimated from the absorption length of the counting rate of EAS.
The attenuation length observed was sensitive to the age parameter and there was a difference between the age parameter estimated from the lateral structure (Slateral) and that from the attenuation of EAS (Slongitudinal) as expressed by the following formula;
Slongitudinal=Slateral+(0.5∼0.8).
The mutual dependence among various parameters (attenuation length, age parameter, size and core structure) led to the following results; (i) Large inelasticity of about 0.7 at E=1014 eV, (ii) The frequent large transverse momentum interactions and (iii) The change of the nuclear interaction mechanism at 1014 eV.
