Equilibrium expectations for non-Gaussian fluctuations near a QCD critical point

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Hauptverfasser: Karthein, Jamie M., Pradeep, Maneesha Sushama, Rajagopal, Krishna, Stephanov, Mikhail, Yin, Yi
Format: Preprint
Veröffentlicht: 2024
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author Karthein, Jamie M.
Pradeep, Maneesha Sushama
Rajagopal, Krishna
Stephanov, Mikhail
Yin, Yi
author_facet Karthein, Jamie M.
Pradeep, Maneesha Sushama
Rajagopal, Krishna
Stephanov, Mikhail
Yin, Yi
contents 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 heavy-ion collision experiments, in which the time spent near a critical point is short.
format Preprint
id arxiv_https___arxiv_org_abs_2409_16249
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Equilibrium expectations for non-Gaussian fluctuations near a QCD critical point
Karthein, Jamie M.
Pradeep, Maneesha Sushama
Rajagopal, Krishna
Stephanov, Mikhail
Yin, Yi
Nuclear Theory
High Energy Physics - Phenomenology
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 heavy-ion collision experiments, in which the time spent near a critical point is short.
title Equilibrium expectations for non-Gaussian fluctuations near a QCD critical point
topic Nuclear Theory
High Energy Physics - Phenomenology
url https://arxiv.org/abs/2409.16249