Long-range rapidity correlations between mean transverse momenta in the model with string fusion

Abstract

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.

The strongly intensive observable in pp collisions at LHC energies in the string fusion model

“…for the case, when we have not string fusion in the given transverse cell. In the last case we find Σ(n F , n B ) = Σ 1 (µ F , µ B ), that in contrast with (8) does not depends on α η .…”

“…Note that the first term with η = 1 corresponds to the contribution from single strings. Obviously, with a change in the initial energy and centrality of pp collisions the portion of the clusters, corresponding to the different number of fused strings, will changes, leading to the change of the weights α η and hence by (8) to the change of the observable Σ(n F , n B ). So, given the possibility of the formation of sources of different types the observable Σ(n F , n B ) becomes equal to the weighted average of the ones for different string clusters with weights, α η , which depend on the details of the collision -the initial energy and centrality of the collision.…”

“…To calculate now the Σ(n F , n B ) by formula (8) we have to make some assumptions on the two-particle correlation function Λ η (y 1 − y 2 ) of a cluster. As in paper [13] we'll use the simplest exponential form Λ η (y…”

“…The Σ(n F , n B ) calculated by formula (8) with the listed parameters is presented in the figure 1 as function of the rapidity distance ∆y between the centers of the observation windows for two values of the window acceptance, δy=0.2 and 0.4, and for two initial energies, 0.9 and 7 TeV.…”

“…We can suppress the influence of these trivial "volume" fluctuations going to the studies of the FB correlation coefficient between the intensive quantities, such as e.g. event-mean transverse momenta p F and p B of charge particles in the observation rapidity intervals δy F and δy B instead of n F and n B , as in [8,9], or defining the more sophisticated correlation observable between n F and n B . In the present paper we'll focus on the last approach.…”