Showing papers in "Progress of Theoretical Physics Supplement in 1971"

Photometric Method in Energy Determination of Cosmic-Ray Showers in Emulsion Chamber

Abstract: Since Japan-Brazil Emulsion Chamber Collaboration started in 1962 on Mt. Chacaltaya, X-ray films have been used together with nuclear emulsion plates for detection of the high energy cosmic· ray showers. Meanwhile, many members, Japanese and Brazilians, of this collaboration have made various attempts to use X-ray film for energy determination as well as for detection. The present work is developed in this basis. Application of the photometric method with X-ray films for energy determination of high energy electron showers gives us the following advantages. Firstly, signal to noise ratio of shower spot on X-ray film is much higher than that on nuclear emulsion plate, because of high sensitivity of X-ray films. Secondly, measurement of spot darkness of shower using micro-densitometer is more facile and more rapid, as compared with counting of electron tracks of the shower in nuclear emulsion plates. Consequently, the photometric method with X-ray film enabled us to make a scale-up of emulsion chamber with great stride. Photometric measurement and track counting method are applied simultaneously to each of 47 showers and the correspondence between spot darkness, Dm .. , and shower energy, Eo, is established empirically. The relation is also calculated with threedimensional shower theory. Both results agree well and give the relation Dm .. cx:E~·85 for various energies. The method of energy determination for localized nuclear interaction in the chamber itself-Ph-jet shower-is also established empirically and theoretically. The same method as for electron shower is valid for Pb-jet showers with energy L: E 7;?1 TeV, if one uses slit larger than 150 p,m radius in micro-densitometer.

Monte Carlo Simulation on Propagation of Cosmic-Rays in the Atmosphere

Abstract: A simulation study is made on propagation and multiplication of the high energy cosmic-ray components in their passage through the atmosphere. The study is planned to simulate observation of high energy cosmic-ray phenomena by the emulsion chambers exposed at high altitude laboratories and to make clear how the observation of such kind will disclose unknown mechanism of the extremely high energy interactions-multiple production of mesons. In particular, the following two models of the multiple meson production are examined in the present simulation: 1) Two-fire-ball model,l> abbreviated as 2F; 2) H-quantum model,2> abbreviated as HQ. The outline of our simulation is as follows. A high energy primary cosmic-ray particle collides with an air nucleus of the upper atmosphere and causes the multiple meson production according to mechanism of the assumed models. The secondary nuclear-active particles, charged n-mesons and an outgoing nucleon, among the generated particles collide in their turn with air nuclei and they develop the so-called nuclear cascade processes while passing through the atmosphere. Gamma-rays, being the decay products of n°-mesons produced by the successive nuclear collisions, are the source of the atmospheric electromagnetic cascade showers. We make a record of particles with energies above a certain threshold energy both of the nuclear-active component and of the electro-magnetic component, which arrived at the observation level. The record consists of data of the arriving particles together with those on the primary particle. The present simulation calculation corresponds to observation of high energy cosmic-ray particles by the emulsion chamber exposed at the mountain altitudes. In particular, it provides us data of the artificial families: identity, energy and spatial distribution of member particles of the families. It is instructive to learn what kind of pattern the artificial families show at the observation plane under a certain assumption. This is indispensable for