Abstract
The long-range correlation between mean-event transverse momenta, being robust against the volume fluctuations and the details of the centrality determination, enables to obtain the signatures of string fusion at the initial stage of hadronic interaction in relativistic heavy ion collisions. The dependence of the correlation strength between mean-event transverse momenta on the collision centrality and initial energy is analyzed in a simple model with quark-gluon string fusion on the transverse lattice. It is shown that above RHIC energy the dependence reveals the decline of the correlation coefficient for most central collisions, reflecting the attenuation of color field fluctuations due to the string fusion at large string density. It is also found that contrary to the correlation between transverse momenta of single particles the strength of the correlation between mean-event transverse momenta of particles in two separated rapidity intervals is not decreasing with the total number of produced strings, remaining significant even in the case of Pb-Pb collisions, in which the total number of strings can reach several thousand.
Highlights
The study of the correlations between observables in two separated rapidity windows has been proposed [1] as a signature of the string fusion and percolation phenomenon [2,3,4,5], which is one of the collectivity effects in ultrarelativistic heavy ion collisions
The MC simulations in the framework of this simple model with string fusion on a transverse lattice enable to calculate the value of the correlation coefficient bpt pt, (4), for an arbitrary value and distribution of mean string density [10]
The results show that the non-monotonic behaviour of bpt pt with centrality is achieved in heavy ion collisions at LHC, while at RHIC the string density is not enough to provide a decline of the correlation coefficient for most central collisions
Summary
The study of the correlations between observables in two separated rapidity windows (the so called long-range forward-backward correlations) has been proposed [1] as a signature of the string fusion and percolation phenomenon [2,3,4,5], which is one of the collectivity effects in ultrarelativistic heavy ion collisions Later it was realized [6,7,8,9,10,11] that the investigations of the forward-backward correlations between intensive observables, such e.g. as mean-event transverse momenta, enable to obtain more clear signal about the initial stage of hadronic interaction, including the process of string fusion, compared to usual forward-backward multiplicity correlations.
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