https://doi.org/10.1140/epjp/s13360-023-04169-w
Regular Article
Exact spin polarization of massive and massless particles in relativistic fluids at global equilibrium
1
Università di Firenze and INFN Sezione di Firenze, Via G. Sansone 1, 50019, Sesto Fiorentino, Florence, Italy
2
Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Straße 1, 60438, Frankfurt am Main, Germany
Received:
18
April
2023
Accepted:
5
June
2023
Published online:
21
June
2023
We present the exact form of the spin polarization vector and the spin density matrix of massive and massless free particles of any spin and helicity at general global equilibrium in a relativistic fluid with non-vanishing thermal vorticity, thus extending the known expression at the linear order. The exact form is obtained by means of the analytic continuation of the relativistic density operator to imaginary thermal vorticity and the resummation of the obtained series. The phenomenological implications for the polarization of the 
hyperon in relativistic heavy-ion collisions are addressed.
© The Author(s) 2023
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