Disentangling Sources of Momentum Fluctuations in Xe+Xe and Pb+Pb Collisions with the ATLAS Detector

ATLAS Collaboration, S. Alderweireldt, J.F. Allen, T.M. Carter, P. J. Clark, J.R. Curran, D. Duda, S. M. Farrington, Y. Gao, R.Y. Gonzalez Andana, C. Jiang, C. Leonidopoulos, M. Firdaus M. Soberi, V. J. Martin, L. Mijović, V.A. Parrish, E.A. Pender, T. Qiu, J.M. Silva, N. ThemistokleousE.M. Villhauer, B.M. Wynne, Z. Xu, E. Zaid

Research output: Contribution to journalArticlepeer-review

Abstract

High-energy nuclear collisions create a quark-gluon plasma, whose initial condition and subsequent expansion vary from event to event, impacting the distribution of the eventwise average transverse momentum [𝑃⁡([𝑝T])]. Disentangling the contributions from fluctuations in the nuclear overlap size (geometrical component) and other sources at a fixed size (intrinsic component) remains a challenge. This problem is addressed by measuring the mean, variance, and skewness of 𝑃⁡([𝑝T]) in 208Pb+208Pb and 129Xe+129Xe collisions at √𝑠NN=5.02 and 5.44 TeV, respectively, using the ATLAS detector at the LHC. All observables show distinct features in ultracentral collisions, which are explained by a suppression of the geometrical component as the overlap area reaches its maximum. These results demonstrate a new technique to separate geometrical and intrinsic fluctuations, providing constraints on initial conditions and properties of the quark-gluon plasma, such as the speed of sound.
Original languageEnglish
Article number252301
Pages (from-to)1-23
Number of pages23
JournalPhysical Review Letters
Volume133
Issue number25
Early online date16 Dec 2024
DOIs
Publication statusPublished - 20 Dec 2024

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