NSF Award
2310021
Experiments involving high-energy heavy-ion collisions at world-leading accelerator facilities such as the Relativistic Heavy Ion Collider (RHIC) in the U.S. and the Large Hadron Collider (LHC) in Europe, are being used to study the constitutive blocks of extreme states matter at high density and temperature. Such studies provide insights regarding the properties of the Universe right after the Big Bang, when elementary particles such as gluons and quarks formed a state of matter known as the quark gluon plasma (QGP) or quark soup. This project will support the development of theory, models and simulations needed to improve our understanding of the QGP formation and its dynamical properties. The project will also support the training of students at the graduate and undergraduate levels. Under the PI’s mentorship the students will acquire practical and analytical skills that will serve them well in their future careers in academia or industry. The computer codes developed by the PI and their students are open source and will provide a testbed for future research for the benefit of the nuclear physics community.<br/><br/>The main goal of this project is to develop the current ZPC parton cascade, which solves the nonlinear relativistic Boltzmann equation, into a dynamical model of finite temperature QCD kinetic theory. Currently ZPC only includes elastic scatterings and treats all flavors with the same two-gluon scattering cross section. In addition, its cross section is determined by a fixed screening mass throughout the parton evolution; this leads to a decrease of the ZPC eta/s with temperature, contrary to the results from pQCD or the Bayesian analysis of available experimental data. Making the screening mass temperature-dependent will lead to the correct temperature-dependence of eta/s. Leading-order inelastic parton processes will be included to describe the chemical equilibration, and flavor-dependent cross sections will be used to properly describe the plasma equilibration. After a determination of the accurate relationship between eta and the parton cross sections, the PI will adjust the screening masses to enable the parton cascade to match the expected QCD shear viscosity including its temperature dependence down to the QCD phase transition temperature.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
