English

Spin polarization and alignment in heavy-ion collisions

Nuclear Experiment 2023-03-22 v1 High Energy Physics - Experiment High Energy Physics - Phenomenology Nuclear Theory

Abstract

We report the measurements of global spin polarization of hyperons (PΛP_{\Lambda}) from FAIR, RHIC and LHC energies. The PΛP_{\Lambda} continue to follow an increasing trend at sNN\sqrt{s_{\mathrm NN}} < 7.7 GeV indicating that enormous vorticity prevail even in hadronic dominant region. New measurements of local spin polarization (Pz,2P_{z,2}) from isobar collisions follow the same pattern observed in previous RHIC and LHC energies. An observable motivated by predicted baryonic Spin Hall Effect, the net local polarization (Pz,2netP_{z,2}^{\mathrm{net}}), shows negative value in Au+Au collisions at sNN\sqrt{s_{\mathrm NN}} = 19.6 and 27 GeV. The first PzP_{z} measurement with respect to third order harmonic in 200 GeV RHIC isobar collisions show a non-zero sine modulation, indicating the presence of complex vortical structure in the medium. Surprising new patterns of spin alignment (ρ00\rho_{00}) for various vector mesons (K0K^{*0}, K±K^{*\pm}, ϕ\phi and J/ψJ/\psi) emerged at both RHIC and LHC energies. The large deviation in ρ00\rho_{00} of several species poses challenge to the theory.

Keywords

Cite

@article{arxiv.2211.13155,
  title  = {Spin polarization and alignment in heavy-ion collisions},
  author = {Subhash Singha},
  journal= {arXiv preprint arXiv:2211.13155},
  year   = {2023}
}

Comments

SQM 2022 proceedings

R2 v1 2026-06-28T06:42:02.906Z