Bayesian constraints on the transport coefficients $η/s$ and $ζ/s$ from spin polarization in relativisitic heavy-ion collisions

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Hauptverfasser: Singh, Sushant K., Grossi, Eduardo, Becattini, Francesco
Format: Preprint
Veröffentlicht: 2026
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author Singh, Sushant K.
Grossi, Eduardo
Becattini, Francesco
author_facet Singh, Sushant K.
Grossi, Eduardo
Becattini, Francesco
contents Bayesian analyses in the context of relativistic heavy-ion collisions have so far relied almost exclusively on bulk hadronic observables constructed from momentum degrees of freedom to constrain the transport properties of the quark-gluon plasma. In this work, we perform the Bayesian inference after incorporating the longitudinal spin polarization of $Λ$ hyperons alongside conventional bulk measurements in Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV to constrain the shear and bulk viscosity to entropy density ratios, $η/s$ and $ζ/s$. We demonstrate that the inclusion of spin polarization, which provides complementary sensitivity to the space-time structure and vorticity of the medium, shifts the posterior distribution of $ζ/s$ toward larger values, although current uncertainties do not allow a statistically significant separation at the 68% credibility level. Nevertheless, the results establish spin polarization as a valuable probe in quantitative studies of QGP transport properties and indicate that it should be incorporated in comprehensive and systematically constrained Bayesian extractions of the medium's dynamical parameters.
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publishDate 2026
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spellingShingle Bayesian constraints on the transport coefficients $η/s$ and $ζ/s$ from spin polarization in relativisitic heavy-ion collisions
Singh, Sushant K.
Grossi, Eduardo
Becattini, Francesco
Nuclear Theory
High Energy Physics - Phenomenology
Bayesian analyses in the context of relativistic heavy-ion collisions have so far relied almost exclusively on bulk hadronic observables constructed from momentum degrees of freedom to constrain the transport properties of the quark-gluon plasma. In this work, we perform the Bayesian inference after incorporating the longitudinal spin polarization of $Λ$ hyperons alongside conventional bulk measurements in Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV to constrain the shear and bulk viscosity to entropy density ratios, $η/s$ and $ζ/s$. We demonstrate that the inclusion of spin polarization, which provides complementary sensitivity to the space-time structure and vorticity of the medium, shifts the posterior distribution of $ζ/s$ toward larger values, although current uncertainties do not allow a statistically significant separation at the 68% credibility level. Nevertheless, the results establish spin polarization as a valuable probe in quantitative studies of QGP transport properties and indicate that it should be incorporated in comprehensive and systematically constrained Bayesian extractions of the medium's dynamical parameters.
title Bayesian constraints on the transport coefficients $η/s$ and $ζ/s$ from spin polarization in relativisitic heavy-ion collisions
topic Nuclear Theory
High Energy Physics - Phenomenology
url https://arxiv.org/abs/2605.29383