Abstract
The initial state, about which there is usually very little direct experimental information, leads to significant fluctuations in the distribution of secondary particles and fragments. In this paper, to estimate the initial state the fragmentation parameters of interacting nuclei are analyzed. To investigate the correlations, the Hurst method is used. A detailed study of event-by-event pseudo-rapidity correlations in terms of the Hurst index, multiplicity of secondary particles and target dependence has been carried out for heavy (AgBr) and light (HCNO) targets present in the nuclear emulsion (NIKFI BR-2) using Au-197 projectiles at 10.6 A GeV. Evidences of short-range particle correlations and cluster formation in the pseudo-rapidity space are found from our analysis. The total ensemble of events has been divided into four classes depending on the behavior of Hurst index: uncorrelated, with short-range correlations, with long-range correlations and mixed. Events of various types differ significantly in the multiplicity of secondary particles, fragmentation of the projectile nucleus, and have significant differences in the pseudo-rapidity distribution of secondary particles.
Highlights
According to the present-day conceptions, the hadron substance transits within the interactions of the nuclei, at the high energies, into a state of the quark-gluon plasma (QGP), in which the quarks and gluons stay in a quasi-free state [1].The study of quark-gluon plasma has mainly focused on two complementary directions
The study of multi-particle correlations and fluctuations in secondary particle distributions is often used to search for quark-gluon plasma, since the formation of secondary particles from a fireball of nuclear matter is of a collective nature [10]
It can be stated that as a result of the interaction of gold nuclei with the nuclei of the NIKFI BR-2 emulsion in some “anomalous” events, two streams of secondary particles are formed with significantly different pseudo-rapidity
Summary
According to the present-day conceptions, the hadron substance transits within the interactions of the nuclei, at the high energies, into a state of the quark-gluon plasma (QGP), in which the quarks and gluons stay in a quasi-free state [1]. The study of multi-particle correlations and fluctuations in secondary particle distributions is often used to search for quark-gluon plasma, since the formation of secondary particles from a fireball of nuclear matter is of a collective nature [10]. It is assumed that, analyzing the data of each individual event in details, it will be possible directly to observe the effects of the phase transition within those events in which the most favorable conditions for the generation of the quark-gluon plasma have been formed. We carried out a joint study of multi-particle correlations and eventby-event pseudo-rapidity fluctuations to search for non-statistical clusters of secondary particles. For this purpose, we analyzed both secondary particles emitted from the interaction region and fragments of the projectile-nucleus and target-nucleus. Analysis of the behavior of the Hurst curve makes it possible to distinguish stochastic fluctuations associated with statistical effects from correlated distributions and to estimate the “strength” and “length” of multi-particle correlations in the pseudo-rapidity distribution of secondary particles [27]
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