Study of Extremely High Energy Hadron Interactions by means of Pamir Cosmic-Ray Experiments.

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The characteristics of extremely high energy hadron interactions is studied through observation of cosmic-ray families and singly arrived hadrons with thick lead x-ray chambers (60cm of Pb) exposed at Pamir altitudes (4200m). X-ray filmes about 3000 m2 have been to sent to Waseda University from Noscow State University after full processings. The total cosmic-ray exposures amount to 57 m^2year with 5 unit chambers of each 10m^2. The main results are summarized as follows.In total 57 cosmic-ray families of visible energy not less than 100 TeV are found and measured. Energy spectra and flux of singly arrived hadrons and gamma-rays of visible energy greater than 4 TeV are obtained by total statistice of 4623 and 3097, respectively, at Pamir altitude (595 g/cm^2). It was found that the fluxes of both families and singly arrived hadrons are far less, about factor 5 or more, than expected from simulation calculations based on the assumption of normal chemical composition of primary cosmic-ra … More ys and ordinary type hadron interactions confirmed upto the CERN collider energy of -100TeV.The attenuation mean free path of high energy hadrons through lead is measured and it gives the consistent balue with geometrical cross section for the hadron interactions, lambda (att) =215(]SY+-[)30g/cm<@D12@>D1 for lead. However, 140high energy hadrons (>10 TeV) in 17 super families of visible energy not less than 700 TeV shows smaller attenuation mean free path. 1 (att) =170+47-26g/cm<@D12@>D1. Such results seems to indicate characteristics of hadron interactions might be changed at much higher energies than the present accelreator experiments.It was found there are several high energy hadron interactions which show abnormal transition behavior through chamber materials, which are never seen in simulation calculation on the basis of ordinary type hadron interactions. In order to study such abnormal characteristics of hadron interactions in different target materials from lead, X-ray films of new chambers with two storyed carbon target have been sent to Waseda from Pamir and the analysis has started and about half of total 96 m^2year exposure have been completed. The report will be presented in near future. Less