Spin relaxation rate for baryons in a thermal pion gas

Journal Article · 16 May 2024 · Physical Review. C

DOI: https://doi.org/10.1103/PhysRevC.109.054909 · OSTI ID:2350988

Hidaka, Yoshimasa; Hongo, Masaru ; Stephanov, Mikhail A.; Yee, Ho-Ung

We study the relaxation dynamics of the spin polarization of baryons (nucleon and $\mathrm{\Lambda }$ baryon), in a thermal pion gas as a simple model of the hadronic phase of the QCD plasma produced in relativistic heavy-ion collisions. For this purpose, we formulate the quantum kinetic theory for the spin density matrix of baryons in the leading order of the gradient expansion. Considering the baryon-pion elastic scattering processes as the dominant interaction between baryons and thermal pions, we compute the spin relaxation rate of nucleons and $\mathrm{\Lambda }$ baryons in a pion gas up to temperature 200 MeV. In the case of nucleons, we evaluate the spin relaxation rate in the $s$ -channel resonance approximation, based on the known experimental data on $\mathrm{\Delta }$ resonances. We also estimate the spin relaxation rate for $\mathrm{\Lambda }$ baryons, based on experimental inputs and theoretical models for the low-energy $\mathrm{\Lambda }\pi$ scattering, including the chiral perturbation theory. Published by the American Physical Society 2024

• Sponsoring Organization: USDOE
• Grant/Contract Number: FG02-01ER41195
• OSTI ID: 2350988
• Journal Information: Physical Review. C, Journal Name: Physical Review. C Journal Issue: 5 Vol. 109; ISSN PRVCAN; ISSN 2469-9985
• Publisher: American Physical SocietyCopyright Statement
• Country of Publication: United States
• Language: English