Polarization phenomenon in heavy-ion collisions

Abstract

The strongly interacting system created in ultrarelativistic nuclear collisions behaves almost as an ideal fluid with rich patterns of the velocity field exhibiting strong vortical structure. Vorticity of the fluid, via spin-orbit coupling, leads to particle spin polarization. Due to the finite orbital momentum of the system, the polarization on average is not zero; it depends on the particle momenta reflecting the spatial variation of the local vorticity. In the last few years, this field experienced a rapid growth due to experimental discoveries of the global and local polarizations. Recent measurements triggered further development of the theoretical description of the spin dynamics and suggestions of several new mechanisms for particle polarization. In this review, we focus mostly on the experimental results. We compare the measurements with the existing theoretical calculations but try to keep the discussion of possible underlying physics at the qualitative level. Future measurements and how they can help to answer open theoretical questions are also discussed. We pay a special attention to the employed experimental methods, as well as to the detector effects and associated corrections to the measurements.

44 pages, 16 figures, Invited review submitted to International Journal of Modern Physics E

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Cited by in corpus (15)

• Hybrid approach to perfect and dissipative spin hydrodynamics
• Spin dynamics with realistic hydrodynamic background for relativistic heavy-ion collisions
• Generalized thermodynamic relations for perfect spin hydrodynamics
• Vector and Tensor Spin Polarization for Vector Bosons at Local Equilibrium
• Mean free path of photons in relativistic heavy ion collisions
• Application range of perfect spin hydrodynamics
• Kubo formulas for spin polarization in dissipative relativistic spin hydrodynamics: a first-order gradient expansion approach
• Second-order spin hydrodynamics from Zubarev's nonequilibrium statistical operator formalism
• Production of $K^{+}{K}^{-}$ Pairs Through Decay of $\varphi$ Meson
• Hybrid framework of Fermi-Dirac spin hydrodynamics
• Global $\Lambda$ polarization in heavy-ion collisions at high baryon density
• Fluid Acceleration in Heavy-Ion Collisions
• Chromomagnetic Condensate in Finite-Temperature SU(2) Yang-Mills Theory under Imaginary Rotation
• Perfect spinfluid: A divergence-type approach
• Rotating synchrotron radiation: Photon emission from magnetized and rotating quark-gluon plasma