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Transport Model Approach to Λ and Λ¯ Polarization in Heavy-Ion Collisions

Authors :
O. V. Vitiuk
Evgeny Zabrodin
Kyrill A. Bugaev
Larissa Bravina
Source :
Symmetry, Volume 13, Issue 10, Symmetry, Vol 13, Iss 1852, p 1852 (2021)
Publication Year :
2021
Publisher :
Multidisciplinary Digital Publishing Institute, 2021.

Abstract

This paper investigates the symmetry breaking between the polarizations of Λ and Λ¯ hyperons in relativistic collisions of heavy ions at intermediate and low energies. The microscopic transport model UrQMD is employed to study the thermal vorticity of hot and dense nuclear matter formed in non-central Au + Au collisions at center-of-mass energies 7.7≤sNN≤62.4 GeV. The whole volume of an expanding fireball is subdivided into small cubic cells. Then, we trace the final Λ and Λ¯ hyperons back to their last interaction point within a certain cell. Extracting the bulk parameters, such as energy density, net baryon density, and net strangeness of the hot and dense medium in the cell, one can obtain the cell temperature and the chemical potentials at the time of the hyperon emission. To do this, the extracted characteristics have to be fitted to the statistical model (SM) of ideal hadron gas. After that, the vorticity of nuclear matter and polarization of both hyperons are calculated. We found that the polarization of both Λ and Λ¯ increases with decreasing energy of heavy-ion collisions. The stronger polarization of Λ¯ is explained by (i) the slightly different freeze-out conditions of both hyperons and (ii) the different space–time distributions of Λ and Λ¯.

Details

Language :
English
ISSN :
20738994
Database :
OpenAIRE
Journal :
Symmetry
Accession number :
edsair.doi.dedup.....31d217bb6bcdbb521c611d917975cfbd
Full Text :
https://doi.org/10.3390/sym13101852