2024/08/08 by Cong Yi, Yi, Cong, Xiang-Yu Wu +7
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2408.04296
We have implemented the 3+1 dimensional CLVisc hydrodynamics model with TRENTO-3D initial conditions to investigate the spin polarization of Λ hyperons along the beam direction in p+Pb collisions at √sNN = 8.16 TeV. Following our previous theoretical framework based on quantum kinetic theory, we consider three different scenarios: Λ equilibrium, s quark equilibrium, and iso-thermal equilibrium scenarios. We have computed the second Fourier sine coefficients of spin polarization along the beam direction, denoted as ⟨ Pz sin 2(ϕp - Ψ2) ⟩, with ϕp - Ψ2 being the azimuthal angle relative to the second-order event plane Ψ2, as functions of multiplicity, transverse momentum and pseudo-rapidity in the three scenarios. Additionally, we have also computed the spin polarization along the beam direction, Pz, as a function of the azimuthal angle. We find that the spin polarization induced by thermal vorticity always provides an opposite contribution compared to the shear-induced polarization in p+Pb collisions. The total spin polarization computed by the current hydrodynamic model disagrees with the data measured by LHC-CMS experiments. Our findings imply that other non-flow effects may play a crucial role in p+Pb collisions.