https://doi.org/10.1051/epjconf/202429605006
Transverse momentum fluctuation in ultra-central Pb+Pb collision at the LHC
1 AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, aleja Mickiewicza 30, 30-059 Cracow, Poland
2 Université Paris Saclay, CNRS, CEA, Institut de physique théorique, 91191 Gif-sur-Yvette, France
3 Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA
4 Physics Department, Brookhaven National Laboratory, Upton, NY 11976, USA
5 Instituto de Física, Universidade de São Paulo, Rua do Matão, 1371, Butantã, 05508-090, São Paulo, Brazil
* e-mail: rsamanta@agh.edu.pl
Published online: 26 June 2024
The ATLAS collaboration has recently observed that the variance of the transverse momentum per particle ([pt]), when measured as a function of the collision multiplicity (Nch) in Pb+Pb collisions, decreases by a factor 2 for the largest values of Nch, corresponding to ultra-central collisions. We show that this phenomenon is naturally explained by invoking impact parameter (b) fluctuations, which contribute to the variance, and gradually disappear in ultracentral collisions. It implies that Nch and [pt] are strongly correlated at fixed b, which is explained by the local thermalization of the QGP medium.
© The Authors, published by EDP Sciences, 2024
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
