Studies of forward–backward multiplicity correlations with the observable Σ at LHC energies: from experimental data to a generalized superposition formalism
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Date
2025
Authors
Sputowska, Iwona
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Publisher
Institute of Nuclear Physics Polish Academy of Sciences
License Type
Creative commons license
Abstract
This paper investigates forward-backward multiplicity correlations in high-energy nucleus-nucleus collisions using the observable Σ, originally defined as a strongly intensive quantity. The aim of this work is to determine what physical information is carried by Σ, how it is connected to other correlation and fluctuation observables, and whether it reflects the genuine dynamics of the collision. The first experimental study of Σ at LHC energies is presented, based on ALICE Xe–Xe collisions at √ sNN = 5.44 TeV and Pb–Pb collisions at √ sNN = 2.76 and 5.02 TeV, with comparison to pp collisions in the energy range √ s = 0.9 − 13 TeV. In heavy-ion collisions, Σ appears independent of the centrality estimator and volume fluctuations, yet shows a clear centrality and system-size dependence. None of the commonly used phenomenological models (HIJING, AMPT, EPOS-LHC) reproduce this behaviour, while pp results are better described by string-based models, suggesting different mechanisms in small and large systems. To interpret these findings, Σ is studied within Wounded Nucleon and Wounded Quark Models. The superposition formalism is then extended to a generalised multisource framework. This approach allows for separating contributions from source number, type, and emission properties. A method for reconstructing the wounded constituent fragmentation function and a Chebyshev expansion link the quantity Σ to the longitudinal structure of the collision. The presented results establish Σ as a robust tool for multi-particle production studies.
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Sponsorship:
National Science Centre, Poland
Grantnumber:
2021/43/D/ST2/02195
License Type
Attribution 4.0 International