Finite density QCD phase structure from strangeness fluctuations

Fuente: arXiv
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Autori principali: Borsányi, Szabolcs, Fodor, Zoltán, Guenther, Jana N., Kumar, Piyush, Parotto, Paolo, Pásztor, Attila, Wong, Chik Him
Natura: Preprint
Pubblicazione: 2025
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author Borsányi, Szabolcs
Fodor, Zoltán
Guenther, Jana N.
Kumar, Piyush
Parotto, Paolo
Pásztor, Attila
Wong, Chik Him
author_facet Borsányi, Szabolcs
Fodor, Zoltán
Guenther, Jana N.
Kumar, Piyush
Parotto, Paolo
Pásztor, Attila
Wong, Chik Him
contents Charting the phase diagram of Quantum Chromodynamics (QCD) at large density is a challenging task due to the complex action problem in lattice simulations. Through simulations at imaginary baryon chemical potential $μ_B$ we observe that, if the strangeness neutrality condition is imposed, both the strangeness chemical potential $μ_S/μ_B$ and the strangeness susceptibility $χ_2^S$ take on constant values at the chiral transition for varying $μ_B$. We present new lattice data to extrapolate contours of constant $μ_S/μ_B$ or $χ_2^S$ to finite baryon chemical potential. We argue that they are good proxies for the QCD crossover because, as we show, they are only mildly influenced by criticality and by finite volume effects. We obtain continuum limits for these proxies up to $μ_B = 400$ MeV, through a next-to-next-to-leading order (N$^2$LO) Taylor expansion based on large-statistics data on $16^3 \times 8$, $20^3 \times 10$ and $24^3 \times 12$ lattices with our 4HEX improved staggered action. We show that these are in excellent agreement with existing results for the chiral transition and, strikingly, also with analogous contours obtained with the hadron resonance gas (HRG) model. On the $16^3 \times 8$ lattice, we carry out the expansion up to next-to-next-to-next-to-next-to-leading order (N$^4$LO), and extend the extrapolation beyond $μ_B=500$ MeV, again finding perfect agreement with the HRG model. This suggests that the crossover line constructed from this proxy starts deviating from the chemical freeze-out line near $μ_B\approx500$ MeV, as expected but not yet observed.
format Preprint
id arxiv_https___arxiv_org_abs_2510_26455
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Finite density QCD phase structure from strangeness fluctuations
Borsányi, Szabolcs
Fodor, Zoltán
Guenther, Jana N.
Kumar, Piyush
Parotto, Paolo
Pásztor, Attila
Wong, Chik Him
High Energy Physics - Lattice
Nuclear Theory
Charting the phase diagram of Quantum Chromodynamics (QCD) at large density is a challenging task due to the complex action problem in lattice simulations. Through simulations at imaginary baryon chemical potential $μ_B$ we observe that, if the strangeness neutrality condition is imposed, both the strangeness chemical potential $μ_S/μ_B$ and the strangeness susceptibility $χ_2^S$ take on constant values at the chiral transition for varying $μ_B$. We present new lattice data to extrapolate contours of constant $μ_S/μ_B$ or $χ_2^S$ to finite baryon chemical potential. We argue that they are good proxies for the QCD crossover because, as we show, they are only mildly influenced by criticality and by finite volume effects. We obtain continuum limits for these proxies up to $μ_B = 400$ MeV, through a next-to-next-to-leading order (N$^2$LO) Taylor expansion based on large-statistics data on $16^3 \times 8$, $20^3 \times 10$ and $24^3 \times 12$ lattices with our 4HEX improved staggered action. We show that these are in excellent agreement with existing results for the chiral transition and, strikingly, also with analogous contours obtained with the hadron resonance gas (HRG) model. On the $16^3 \times 8$ lattice, we carry out the expansion up to next-to-next-to-next-to-next-to-leading order (N$^4$LO), and extend the extrapolation beyond $μ_B=500$ MeV, again finding perfect agreement with the HRG model. This suggests that the crossover line constructed from this proxy starts deviating from the chemical freeze-out line near $μ_B\approx500$ MeV, as expected but not yet observed.
title Finite density QCD phase structure from strangeness fluctuations
topic High Energy Physics - Lattice
Nuclear Theory
url https://arxiv.org/abs/2510.26455