https://doi.org/10.1140/epjp/s13360-024-04862-4
Regular Article
In-medium electromagnetic form factors and spin polarizations
School of Physics and Astronomy, Sun Yat-Sen University, 519082, Zhuhai, China
Received:
28
August
2023
Accepted:
3
January
2024
Published online:
1
February
2024
Despite significant progress having been made in understanding spin polarization phenomena in relativistic heavy ion collisions, the underlying assumption of weakly coupled medium is not well justified. To go beyond this limitation, we formulate spin polarization in background electromagnetic fields using form factors. We show that the form factors at tree level in vacuum reproduce the spin polarization effects found in chiral kinetic theory. The vacuum form factors corresponding to spin couplings to perpendicular electric fields, parallel and perpendicular magnetic fields are degenerate. The degeneracy can be lifted in medium. As an example, we calculate the in-medium QCD radiative corrections to the form factors at one-loop order, where we find partial lift of the degeneracy: The spin couplings to parallel and perpendicular magnetic fields are different, but the spin couplings to perpendicular electric and parallel magnetic fields remain the same.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2024. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.