Resumo: At extremely high temperature there exists a state of matter called the quark-gluon plasma, where the fundamental constituents of most ordinary matter -- quarks and gluons -- are not confined into color-neutral protons and neutrons, and instead color degrees of freedom are liberated. Collisions between heavy atomic nuclei at ultrarelativistic energies are carried out at particle colliders in order to produce this phase of matter. Despite two decades of investigation, one of the big open challenges has been to obtain a clear experimental determination of the number of thermodynamic degrees of freedom, and therefore direct confirmation that a deconfined phase of matter is produced. This can be done by determining the temperature reached in a heavy-ion collision, and a simultaneous determination of another thermodynamic quantity at that temperature, such as the entropy density, that would give access to the number of degrees of freedom. In this colloquium I present such a determination, obtained using state-of-the-art hydrodynamic simulations. Our results agree with first-principles calculations from lattice quantum chromodynamics and confirm that a deconfined phase of matter is indeed produced, at the highest temperatures ever achieved by humans.
Referência: F. Gardim, G. Giacalone, M. Luzum, J-Y. Ollitrault; Nature Phys. 16 (2020) 6, 615-619 https://rdcu.be/b3i1Q Sobre o Palestrante: Matthew Luzum é Professor no Departamento de Física Matemática do IFUSP. Doutorado pela University of Washington, foi pesquisador visitante na Universidade de Santiago de Compostela. Tem experiência na área de Física de Partículas, com ênfase em hidrodinâmica viscosa relativística, cromodinâmica quântica e plasma de quarks e glúons. Palavras-chaves: Quark Gluon Plasma; Quantum Chromodynamics;Thermodynamics
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