Seminar “Theory of Hadronic Matter under Extreme Conditions”

Date and Time: Wednesday, 25 November 2020, at 5:00 PM

Venue: Online conference in Zoom, Bogoliubov Laboratory of Theoretical Physics

Seminar topic: “Core meets corona: Lambda and anti-Lambda polarization in peripheral high-energy heavy-ion collisions»

Speaker: Alejandro Ayala (Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico)

Abstract:

The STAR Beam Energy Scan program has found a remarkable behaviour for the global polarization of Lambdas and anti-Lambdas produced in peripheral high-energy Au + Au collisions: the latter is larger than the former for lower collision energies and the difference decreases with increasing collision energy. In this talk, I show that a two-component source to model the collision region, consisting of a high density core and a lower density corona, can quantitatively describe the behaviour of these polarizations as functions of the collision energy. The calculation makes use of the relaxation times that s-quarks and -antiquarks produced in the core take to align with the thermal vorticity during the life-time of the quark-gluon plasma phase that I also show how can be computed from a thermal field theoretical approach. I show that, in spite of the fact that s-antiquarks (that hadronize into anti-Lambdas) take longer to align their spins compared to s-quarks (that hadronize into Lambdas) when combining this information with the larger abundance of Lambdas compared to anti-Lambdas in the corona, the polarization excitation function can be well described.