Long-range Multiplicity Correlations Research Articles

Pseudorapidity window size dependence of multiplicity fluctuations in high-energy collisions with system size and beam energies

An investigation of the critical behavior of strongly interacting quantum chromodynamics (QCD) matter has been performed by analyzing fluctuation observables on event-by-event (ebe) basis measured in high-energy collision experiments. The fluctuation analysis is performed using nuclear interactions at different target sizes and at different colliding beam energies as a function of varying width of pseudorapidity interval. For the sake of comparison, ebe multiplicity fluctuations in hadronic and heavy ion collisions (p–H, p–A and A–B) are studied within the framework of the Lund Monte Carlo-based FRITIOF model. Charged particle multiplicity and the variance of the multiplicity distribution are estimated for the interactions involving different target sizes and beam momenta, i.e., p–H, p–CNO, p–AgBr at 200 A GeV/c and [Formula: see text]O–AgBr collisions at 14.6 A, 60 A and 200 A GeV/c. Further, multiplicity fluctuations are quantified in terms of intensive quantity, the scaled variances [Formula: see text] and the strongly intensive quantity [Formula: see text] derived from the charged particle multiplicity and the width of the multiplicity distribution. Strongly intensive quantity [Formula: see text] is a quantity of great significance to extract information about short- and long-range multiplicity correlations. Furthermore, the collision centrality and centrality bin width-dependent behavior of the multiplicity fluctuation have been examined in the framework of Lund Monte Carlo-based FRITIOF model. Results based on the fluctuation analysis carried out in this study are interpreted in terms of dynamics of collision process and the possibility of related QCD phase transition.

Pseudorapidity dependence of multiplicity and transverse momentum fluctuations at the SPS energies

A search for the critical behavior of strongly interacting matter was done by studying the event-by-event fluctuations of multiplicity and transverse momentum of charged hadrons produced in inelastic p+p collisions and central Be+Be and Ar+Sc collisions at the NA61/SHINE experiment. Results for energy dependence of the scaled variance of the multiplicity distribution and for two families of strongly intensive measures of multiplicity and transverse momentum fluctuations Δ[PT, N] and Σ[PT, N] were presented. The study was performed in rapidity-integrated way and for different pseudorapidity regions, which corresponds to changing the rapidity averaged baryo-chemical potential and the value of temperature at the freeze-out stage. The strongly intensive measure Σ[NF, NB], evaluated in rapidity separated windows, was used in the analysis of short- and long-range multiplicity correlations and is considered to be sensitive for the initial conditions of particle production such as string fragmentation and fusion.

Azimuthal anisotropy of long-range correlations at LHC energy in Monte Carlo model with string fusion

Long-range multiplicity correlations in intervals separated in pseudorapidity and azimuth are studied in the framework of string fusion approach. We applied a Monte Carlo model, in which the string configurations in the transverse plane and rapidity are simulating event-by-event. The string interaction is realized in the lattice string fusion approach with introduction of a grid in the transverse plane. We assumed that the azimuthal anisotropy of particle production is caused by parton energy loss traveling trough the media formed by clusters of fused strings : Δpt /Δx = −α (pt √η )2/3 , where η is a string density. In the cellular approach the Bresenham’s line algorithm has been applied. It is obtained that in AA collisions, the parton energy loss seems to play considerable role, in particular, by providing large contribution to the correlation of mean transverse momentum with multiplicity. The developed approach provides non-zero values flows in p-Pb collisions at LHC energies and produces the pattern similar to the one of the experimental di-hadron analysis.

Probing the quark-gluon phase transition using energy and system-size dependence of long-range multiplicity correlations in heavy ion collisions from the STAR experiment

Long-range forward-backward multiplicity correlations have been measured in heavy ion collisions at RHIC. Results for short and long-range multiplicity correlations (forward-backward) are presented for several systems (Au+Au, Cu+Cu, and pp) and energies (e.g. \(\sqrt {s_{NN} } \) = 200 and 62.4 GeV). A strong, long-range correlation is seen for central heavy ion collisions at \(\sqrt {s_{NN} } \) = 200 GeV that vanishes in semi-peripheral events and pp collisions. There is no apparent scaling with the number of participants (N part) involved in the collision. These correlations provide information about the longitudinal behavior of the system formed in heavy ion collisions. To access the transverse behavior, the clusters produced in the same heavy ion collisions have been characterized by a study of the energy and system size dependence of the percolation density parameter (ρ). The relationship between the long-range correlation and percolation has been explored to characterize the hadron-quark/gluon phase transition and rapid thermalization of the system.

FORWARD-BACKWARD MULTIPLICITY CORRELATIONS IN Au+Au COLLISIONS AT $\sqrt{s_{NN}} = 200\, {\rm GeV}$

The study of correlations among particles produced in different rapidity regions may provide understanding of the mechanisms of particle production. Correlations that extend over a longer range are observed in hadron-hadron interactions only at higher energies. Results for short and long-range multiplicity correlations (Forward-Backward) are presented for Au + Au collisions at [Formula: see text]. The growth of long range correlations are observed as a function of the pseudorapidity gap in central Au + Au collisions. The Dual Parton model and Color Glass Condensate phenomenology have been explored to understand the origin of long range correlations.

ENERGY DEPENDENCE OF SHORT AND LONG-RANGE MULTIPLICITY CORRELATIONS IN Au+Au COLLISIONS FROM STAR

A general overview of the measurement of long-range multiplicity correlations measured by the STAR experiment in Au + Au collisions at RHIC is presented. The presence of long-range correlations can provide insight into the early stages, and the type of matter produced in, these collisions. These measurements have been made in Au + Au collisions at [Formula: see text] and 62.4 GeV. These results indicate a relatively large long-range correlation is produced in Au + Au collisions compared to a pp baseline at [Formula: see text]. A weaker long-range correlation is seen as a function of incident energy. Further, comparison of the onset of the long-range correlation to the calculated percolation density parameter at [Formula: see text] is presented.