The Bin-bin Multiplicity Correlation Of Rapidity Phase Space In Relativistic Heavy Ion Collisions

It is generally considered that quark and lcpton arc the component units of matter. But in so many experiments, free quark has not been observed yet. Quarks and gluons are confined in hadrons so that there are no free quarks. This is called "quark confinement" or "color confinement", which is thought as a great puzzle of 20th century. In the 1970s of 20th century, T.D.Lee et al. proposed that through high energy heavy ion collisions a new state of matter——quark gluon plasma (QGP) would be produced. QGP consists of a large amount of deconfined quarks, antiquarks and gluons. This prediction has substantially promoted theoretical and experimental study on relativistic heavy ion collision.Because of color confinement, we can't see free partons——quarks and gluons, only hadrons can be observed. But these final state hadrons carry much information about quarks and gluons. So studying the final state of multi-particle systems can help us better understand the initial state and the process of collisions. Correlation is a powerful tool for exploring the complex dynamical mechanisms of multi-particle sys-tems. The observable used in this paper——neighboring bin and fixed-to-arbitrary bin correlation patterns, depend on the bin positions. So they can reflect the de-pendence not only on the correlation length but also on the spatial position. In this paper, we use these two correlation patterns to study multi-particle systems produced in relativistic heavy ion collisions.Recently long range rapidity correlation has been observed in central Au+Au col-lisions at RHIC. But people are still not clear about the source of long range rapidity correlations. Some theories like dual parton model(DPM) and color glass conden-sate(CGC), hold that long range rapidity correlations come from parton interactions. However, results from our study question these accounts. The centrality and energy dependence of rapidity correlation patterns are studied for Au+Au collisions by AMPT(with string melting), RQMD and UrQMD. The behaviors of the short-range correlation (SRC) and the long-range correlation (LRC) are presented clearly by the two spatial-position dependent correlation patterns.For centrality dependence, three models give similar results. In peripheral col-lision, the correlation strength drops as the correlation length becoming longer; in most central collision the correlation structure is flatter and the correlation range is larger, which indicates a long range rapidity correlation. Both RQMD and UrQMD arc hadron-based transport models, having no parton interaction. Long range rapid-ity correlation showing up in RQMD and UrQMD implies that parton interaction is not the only source of long range rapidity correlations; long range rapidity corre-lations may come from other mechanisms, such as hadron rescattering and hadron transport, etc.For energy dependence. AMPT and RQMD show quite different results. The correlation patterns in RQMD at low collision energies and those in AMPT at high collision energies have similar structures, i.e. a convex curve. While in RQMD at high collision energies and in AMPT at low collision energies, the correlation pat-terns show flat structures, having no position dependence and having long correlation length. Long range rapidity correlation presents itself at high energy and disappears at low energy in RQMD, which again implies that long range rapidity correlations may come from some trivial effects, rather than the parton interactions.