Lambda polarization in heavy ion collisions: from RHIC BES to LHC energies

Abstract

STAR collaboration at RHIC has recently measured the polarization of $\Lambda$ hyperons in non-central heavy ion collisions in the RHIC Beam Energy Scan (BES) program. The magnitude of the polarization was found to decrease from few percents at the lowest BES energies to $\approx 0.2$% at the top RHIC energy. The polarization signal has been reproduced in different hydrodynamic calculations assuming a thermodynamic spin-vorticity coupling mechanism at the Cooper-Frye hypersurface. In this work an extension of our existing calculations of the $\Lambda$ polarization in the RHIC BES program to the top RHIC and 2.76 TeV LHC energies is presented. The longitudinal component of the $\Lambda$ polarization, which is the dominant component of the polarization at the LHC energies, is discussed. Finally we show that the global polarization of $\Lambda$ originates dominantly from the relativistic analogue of the classical vorticity, whereas the quadrupole longitudinal component originates from the gradients of temperature and acceleration of the medium when the $\Lambda$s are produced out of the fluid.

talk given at Quark Matter 2018 conference (Venice, Italy, 13-19 May 2018). 4 pages, 2 figures

References in corpus (6)

• Global polarization of $\Lambda$ hyperons in Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV
• Collective longitudinal polarization in relativistic heavy-ion collisions at very high energy
• Global $\Lambda$ Polarization in high energy collisions
• Lambda hyperon polarization in relativistic heavy ion collisions from the chiral kinetic approach
• Directed flow in ultrarelativistic heavy-ion collisions
• Transverse-momentum fluctuations in relativistic heavy-ion collisions from event-by-event viscous hydrodynamics

Cited by in corpus (17)

• Polarization and Vorticity in the Quark Gluon Plasma
• Local spin polarization in high energy heavy ion collisions
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• A hydrodynamic study of hyperon spin polarization in relativistic heavy ion collisions
• Longitudinal spin polarization in a thermal model
• Relaxation time for quark spin and thermal vorticity alignment in heavy-ion collisions
• Λ polarization from thermalized jet energy
• Relaxation time for the alignment between the spin of a finite-mass quark/antiquark and the thermal vorticity in relativistic heavy-ion collisions
• Hyperon polarization and its relation with directed flow in high-energy nuclear collisions
• Fermion propagator in a rotating environment
• Calculation of acceleration effects using the Zubarev density operator
• Holography of Low-Centrality Heavy Ion Collisions
• Vorticity and Polarization in Heavy Ion Collisions: Hydrodynamic Models
• Temperatures and chemical potentials at kinetic freeze-out in relativistic heavy ion collisions from coarse grained transport simulations
• Polarized baryon production in heavy ion collisions: an analytic hydrodynamical study
• Comment on "Evaluation of kinetic freeze-out properties in different relativistic heavy-ion collision systems at \sqrtsNN = 200 GeV'' (Eur. Phys. J. Plus (2025) 140:179) https://doi.org/10.1140/epjp/s13360-025-06119-0
• Global polarization and spin alignment measurements