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Topical discussion:"Spin polarization: theoretical update and experimental perspective"

Speaker: Francesco Becattini (University of Florence)
                    Huichao Song (Peking University) 

Time: Nov. 23(Tuesday)  6:00am (San Fransisco), 9:00am (New York), 3:00pm (Frankfurt), 6:30pm(New Delhi), 9:00pm (Beijing), 10:00pm (Tokyo)


1. Spin is a relatively new an intruguing topic in the rather mature field of relativistic heavy ion collisions. The predictions of the hydrodynamic model of the Quark Gluon Plasma, providing the proportionality between spin polarization vector and thermal vorticity,
have been confirmed by the measurements of global spin polarization of Lambda hyperons in peripheral collisions. However, the measurements of spin polarization as a function of the hyperon momentum revealed consistent discrepancies with respect to the theoretical predictions. In this talk, I will present a recent theoretical development which apparently implies a solution of the local polarization puzzles. The covariant theory of quantum relativistic fluids at local equilibrium indeed predicts an additional term, hitherto overlooked, of the spin polarization vector which is proportional to the shear tensor.
This additional contribution is able to reconcile the theory with the experimental data at the highest RHIC energy if the Quark-Gluon Plasma hadronizes at a fixed temperature.

2. In the first part of my talk, I will quickly review the local lambda polarization puzzle within hydrodynamic framework using the traditional spin Cooper-Frye formular with thermal vorticity[1]. Then I will demonstrate that the shear-induced polarization, obtained from the quantum kinetic equation and linear response theory, could give a right sign to the local lambda polarization at top RHIC and LHC energies [2]. In the second part of my talk, I will focus on the spin hall effects (SHE), a missing spin polarization mechanism in previous study, and discuss the sensitive experimental observables that could/might discover the SHE for the hot and dense QCD matter created at RHIC-BES energies [3]. At last, I will compare and discuss the formulism and numerical simulations for spin polarization with the shear effects from the Becattini group and our group.     

Chair:   Dirk H. Rischke(Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität)

ZOOM link: Please register here, the ZOOM link will be send in the comming Tuesday by group email. By attending this event you agree to the seminar and discussion being recorded and posted on the seminar web site.

Material: https://indico.ihep.ac.cn/event/15874/material/slides/


Starts Nov 23, 2021 21:00
Ends Nov 23, 2021 22:30