Fluctuations and correlations in STAR

Abstract

Abstract. The study of correlations and fluctuations can provide evidence for the production of the quarkgluon plasma (QGP) in relativistic heavy ion collisions. Various theories predict that the production of a QGP phase in relativistic heavy ion collisions could produce significant event-by-event correlations and fluctuations in, transverse momentum, multiplicity, etc. Some of the recent results using STAR at RHIC will be presented along with results from other experiments at RHIC. The focus is on forward-backward multiplicity correlations, balance function, charge and transverse momentum fluctuations, and correlations.PACS. 25.75.-q Relativistic heavy-ion collisions, 25.75.Gz Particle correlations

Entropy Analysis in Relativistic Heavy-Ion Collisions

“…This prompts one to study multiplicity fluctuations by comparing the ebe multiplicity, , in a pseudorapidity window of width Δ placed in the F region with the multiplicity observed in an identical window in the B region; the two windows are chosen in such a way that they are symmetric around . Using these definitions, a number of attempts have been made to investigate F-B multiplicity correlations and fluctuations either by examining the dependence of on ⟨ ⟩ [42][43][44][45][46] or by considering [30,[38][39][40][41] investigations observe presence of strong F-B correlations. Such correlations are believed to arise due to isotropic decays of cluster-like objects in F or B region.…”

“…The observed difference in the entropy values in the two regions for the experimental and AMPT events (and not with the IEH events) may arise due to the strong correlations existing between the particles belonging to the adjacent F and B regions around midrapidity [9,[39][40][41]. It is commonly believed [38][39][40][41][42][43][44][45][46] that the forward-backward correlations observed are of short-range type and there are almost no or very small contributions from the long-range correlations, particularly at lower energies. In order to ensure further that whether or not the observed entropy difference arises due to the particle correlations of short-range type, entropy values are calculated in F and B regions after leaving a gap of 2 units It is interesting to note in Figure 5 that the entropy difference in the two regions is much smaller as compared to those reflected from Figure 3.…”

Search for Long-Range Correlations in Relativistic Heavy-Ion Collisions at SPS Energies

“…For AA collisions, the multiparton interactions are expected to give rise to LRC, which would extend to rather longer range as compared to those observed in hh collision at the same incident energy [6,15,20,21]. The color glass condensate picture of particle productions and the multiple scattering model also predict presence of LRC in AA collisions [6,8,15,20,22,23].…”