Strongly Intensive Observables in the Model with String Fusion

Abstract

We calculate the strongly intensive observables for multiplicities in two rapidity windows in the model with independent identical strings taking into account the charge sign of particles. We express the observables through the string pair correlation functions describing the correlations between the same and opposite sign particles produced in a string decay. We extract these charge-wise string two-particle correlation functions from the ALICE data on the forward-backward correlations and the balance function. Using them we predict the behavior of the charge-wise strongly intensive observables in the model with independent identical strings. We also show that the observable between multiplicities in two acceptance windows separated in rapidity, which is a strongly intensive in the case with independent identical strings, loses this property, when we take into account string fusion effects and a formation of strings of a few different types takes place in a collision. We predict the changes in the behaviour of this observable with energy and collision centrality, arising due to the string fusion phenomena.

On the Interpretation of the Balance Function

“…As mentioned in the Introduction, the ν s (δη) is simply connected with the balance function B(η 1 − η 2 ). In any model with identical independent sources in the central region, where the translation invariance in rapidity and the charge symmetry take place, we have (see, e.g., Section 5 of the paper [8]):…”

“…where ρ + (η), ρ +− (η 1 , η 2 ), etc., are the inclusive and double inclusive pseudorapidity distributions of corresponding charged particles (for the correspondence with other possible alternative definitions of the BF see, e.g., [8]).…”

On the Interpretation of the Balance Function

“…Using now definition (5) we express the ν s (δη) through the correlation functions C +− and C ++ by the model independent way:…”

“…In any model with the identical independent sources in the central region, where the translation invariance in rapidity and the charge symmetry take place, we have (see e.g. Section 5 of the paper [5]):…”

“…where ρ + (η), ρ +− (η 1 , η 2 ) and so on are the inclusive and double inclusive pseudorapidity distributions of corresponding charged particles (on the correspondence with other possible alternative definitions of the BF see e.g. [5]).…”