Investigations of azimuthal and rapidity effects at multiparticle production

Abstract

Before the time of the operation of new accelerators at CERN in Geneva, Chicago m USA and Dubna iu USSR, most of the basic knowledge about the interaction of fundamental particles came from the studies of cosmic-ray physics. One of the interesting things studied was the angular distribution of the tracks of relativistic particles produced in the cosmic-ray primary jets. In those high-energy interactions it was noticed that in some of the individual interactions, secondary particles were not distributed in rotational symmetry around the direction of the incident nucleus but instead showed a tendency to cluster near a preferential plane and an azimuthal asymmetry was observed. But when wc consider the collective angular distribution of large number of primary events, the azimuthal asymmetry, observed in some individual events in a plane perpendicular to the collision axis, disappears due to the statistical fluctuations in the angular distribution. Among the different models used for the studies of the mechanism of high-energy particle production, the fireball model (1), proposed about 20 years ago, explained best the dynamics of ultra high-energy interactions. In fact the fireball idea was a very fruitful one. It provided the building blocks for many models of particle production. Indeed, almost any model o~ particle production was generated into a model of fireball production. Detection of the production of fireball is generally done through the angular distribution which is commonly plotted in terms of x variable where x ~ In tg 0~. and 0 L is the polar angle of the emitted particle with respect to the incident particle. This angular distribution helps one to understand whether the particles are produced from one fireball or two fireballs. The shape of the angular distribution determines the dispersion (a) which is a measure of the degree of auisotropy. For one center, we use a 0.90. In cosmic-ray studies (2) as well as in (~) P. CIOK, T. COGIIEN, 5. GIERULA, R. HOLYNSKI, A. 5UI~AK, ~r 1VIII~SOWICZ, T. SANIEWSKA an4 O. STXNISZ: NUOVO Cimento, 8, 166 (1958); 1O, 741 (1958); G. CocooN1: Phys. Rev., 111, 1699 (1958);