High-order cumulants and correlation functions near the critical point from molecular dynamics
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| Format: | Preprint |
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2025
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| _version_ | 1866911252914110464 |
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| author | Kuznietsov, Volodymyr A. Poberezhniuk, Roman Gorenstein, Mark I. Koch, Volker Vovchenko, Volodymyr |
| author_facet | Kuznietsov, Volodymyr A. Poberezhniuk, Roman Gorenstein, Mark I. Koch, Volker Vovchenko, Volodymyr |
| contents | We present a systematic investigation of particle number fluctuations in the crossover region near the critical endpoint of a first-order phase transition using molecular dynamics simulations of the classical Lennard-Jones fluid. We extend our prior studies to third- and fourth-order cumulants in both coordinate- and momentum-space acceptances and integrated correlation functions (factorial cumulants). We find that, even near the critical point, non-Gaussian cumulants equilibrate on time scales comparable to those of the second-order cumulants, but show stronger finite-size effects. The presence of interactions and of the critical point leads to strong deviations of the cumulants from the ideal-gas baseline in coordinate space; these deviations are expected to persist in momentum space in the presence of collective expansion. In particular, the kurtosis becomes strongly negative, $κσ^2 \ll -1$, on the crossover side of the critical point. However, this signal is significantly diluted once an efficiency cut used to distinguish protons from baryons is applied, leading to $|κσ^2| \lesssim 1$ even in the presence of the critical point. We discuss our results in the context of ongoing measurements of proton number cumulants in heavy-ion collisions in RHIC-BES-II. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2511_00755 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | High-order cumulants and correlation functions near the critical point from molecular dynamics Kuznietsov, Volodymyr A. Poberezhniuk, Roman Gorenstein, Mark I. Koch, Volker Vovchenko, Volodymyr Nuclear Theory High Energy Physics - Phenomenology We present a systematic investigation of particle number fluctuations in the crossover region near the critical endpoint of a first-order phase transition using molecular dynamics simulations of the classical Lennard-Jones fluid. We extend our prior studies to third- and fourth-order cumulants in both coordinate- and momentum-space acceptances and integrated correlation functions (factorial cumulants). We find that, even near the critical point, non-Gaussian cumulants equilibrate on time scales comparable to those of the second-order cumulants, but show stronger finite-size effects. The presence of interactions and of the critical point leads to strong deviations of the cumulants from the ideal-gas baseline in coordinate space; these deviations are expected to persist in momentum space in the presence of collective expansion. In particular, the kurtosis becomes strongly negative, $κσ^2 \ll -1$, on the crossover side of the critical point. However, this signal is significantly diluted once an efficiency cut used to distinguish protons from baryons is applied, leading to $|κσ^2| \lesssim 1$ even in the presence of the critical point. We discuss our results in the context of ongoing measurements of proton number cumulants in heavy-ion collisions in RHIC-BES-II. |
| title | High-order cumulants and correlation functions near the critical point from molecular dynamics |
| topic | Nuclear Theory High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2511.00755 |