Extracting the QCD speed of sound in the presence of quantum fluctuations
Abstract
The equation of state of strongly interacting matter plays a %is one of the central quantities characterizing central role in characterizing quark--gluon plasma created in relativistic heavy-ion collisions. It has recently been recognized that the QCD speed of sound is responsible for the linear correlations between the mean transverse momentum and charged-particle multiplicity in ultra-central collisions. In realistic collisions, however, this thermodynamic correlation is inevitably biased by quantum-initiated event-by-event fluctuations. In this work, we present a novel statistical framework to correct this bias by leveraging the Gaussianity condition of the quantum fluctuations. Furthermore, we demonstrate that this approach can also serve as a probe of thermalization. Validated by the event-by-event hydrodynamic simulations, the extracted speed of sound in our framework is successfully consistent with the predictions from lattice QCD, from large to small collision systems.
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BibTeX
@misc{mu2026extracting,
title = {{Extracting the QCD speed of sound in the presence of quantum fluctuations}},
author = {Yu-Shan Mu and Li Yan and Xu-Guang Huang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.36846},
eprint = {2610.36846},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.36846},
}
RIS
TY - UNPB
TI - Extracting the QCD speed of sound in the presence of quantum fluctuations
AU - Yu-Shan Mu
AU - Li Yan
AU - Xu-Guang Huang
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.36846
UR - https://arxiv.org/abs/2610.36846
AB - The equation of state of strongly interacting matter plays a %is one of the central quantities characterizing central role in characterizing quark--gluon plasma created in relativistic heavy-ion collisions. It has recently been recognized that the QCD speed of sound is responsible for the linear correlations between the mean transverse momentum and charged-particle multiplicity in ultra-central collisions. In realistic collisions, however, this thermodynamic correlation is inevitably biased by quantum-initiated event-by-event fluctuations. In this work, we present a novel statistical framework to correct this bias by leveraging the Gaussianity condition of the quantum fluctuations. Furthermore, we demonstrate that this approach can also serve as a probe of thermalization. Validated by the event-by-event hydrodynamic simulations, the extracted speed of sound in our framework is successfully consistent with the predictions from lattice QCD, from large to small collision systems.
ER -