Issue |
EPJ Web Conf.
Volume 316, 2025
The 21st International Conference on Strangeness in Quark Matter (SQM 2024)
|
|
---|---|---|
Article Number | 06016 | |
Number of page(s) | 4 | |
Section | Bulk Matter Phenomena, QCD Phase Diagram and Critical Point | |
DOI | https://doi.org/10.1051/epjconf/202531606016 | |
Published online | 27 January 2025 |
https://doi.org/10.1051/epjconf/202531606016
Equilibrium expectations for non-Gaussian fluctuations near a QCD critical point
1 Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
2 Department of Physics, University of Maryland, College Park, Maryland 20742, USA
3 Department of Physics, University of Illinois, Chicago, Illinois 60607, USA
4 School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong, 518172, China
* e-mail: jmkar@mit.edu
Published online: 27 January 2025
With the highly anticipated results from the Beam Energy Scan II program at RHIC being recently revealed, an understanding of particle-number fluctuations and their significance as a potential signature of a possible QCD critical point is crucial. Early works that embarked on this endeavor sought to estimate the fluctuations due to the presence of a critical point assuming they stay in equilibrium. From these results came the proposal to focus efforts on higher, non-Gaussian, moments of the event-by-event distributions, in particular of the number of protons. These non-Gaussian moments are especially sensitive to critical fluctuations, as their magnitudes are proportional to high powers of the critical correlation length. As the equation of state provides key input for hydrodynamical simulations of heavy-ion collisions, we estimate equilibrium fluctuations from the BEST equation of state (EoS) that includes critical features from the 3D Ising Model. In particular, the proton factorial cumulants and their dependence on non-universal mapping parameters is investigated within the BEST EoS. Furthermore, the correlation length, as a central quantity for the assessment of fluctuations in the vicinity of a critical point, is also calculated in a consistent manner with the scaling equation of state. An understanding of the equilibrium estimates of proton factorial cumulants will be useful for further comparison to estimates of out-of-equilibrium fluctuations in order to determine the magnitude of the observable fluctuations to be expected in heavyion collision experiments, in which the time spent near a critical point is short.
© The Authors, published by EDP Sciences, 2025
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