Browsing by Author "Rapp, Ralf"

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Microscopic Properties of Hot and Dense QCD Matter
Cyclotron Institute; TAMU; https://hdl.handle.net/20.500.14641/494; National Science Foundation
A few micro-seconds into the cooling process of the early Universe, an extremely hot plasma of elementary particles (quarks and gluons) condensed into bound states called hadrons, the building blocks of the visible matter in the Universe. The condensation of the quark-gluon plasma (QGP) confined the quarks and gluons into hadrons and generated about 98% of the visible mass. The discovery of the mechanisms of quark confinement and hadron mass generation are central goals of fundamental research in particle and nuclear physics. Experimentally, small droplets of QGP, at record temperatures exceeding 2 trillion Kelvin, can be re-created in the laboratory by colliding atomic nuclei at high energies, at the Relativistic Heavy-Ion Collider and the Large Hadron Collider. However, it is very challenging to infer the properties of the QGP and its hadronization from the measured particle spectra. The PI, together with his graduate students and collaborators, will develop theoretical methods and apply them to unravel fundamental properties of the QGP from experimental data. His research and educational activities also encompass undergraduate research and outreach to high-school students within the Saturday Morning Physics program at Texas A&M. The heavy charm and bottom quarks, as well as electromagnetic (EM) radiation, are particularly valuable probes of the QGP. The PI will use state-of-the-art quantum many-body theory of the strong nuclear force to analyze the diffusion of heavy quarks (Brownian motion) and their subsequent hadronization. A systematic analysis of the experimental spectra of baryons (3-quark states) and mesons (quark-antiquark states) containing heavy quarks will unravel mechanisms of hadronization and provide unprecedented precision in the extraction of the heavy-quark diffusion coefficient, a key quantity to characterize the interaction strength in the QGP. The PI will further use EM radiation, which can penetrate the QGP formed in heavy-ion collisions, to analyze the mechanism of mass generation. He will investigate the spectral modifications of baryons near the hadronization transition and extract the electric conductivity, another fundamental transport parameter of the medium. 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.
Radiation and Transport in QCD Matter
Cyclotron Institute; TAMU; https://hdl.handle.net/20.500.14641/494; National Science Foundation
A few micro-seconds after the Big Bang the universe was filled with an extremely hot plasma made of elementary particles, the quarks and gluons. When the expanding plasma cooled to a temperature of about two trillion degrees, quarks and gluons condensed into massive bound states called hadrons, including the protons and neutrons which make up the atomic nuclei of the matter around us. This transition generated over 95% of the visible mass in the universe, and it permanently confined quarks and gluons into hadrons. How these phenomena emerge from the strong nuclear force between quarks and gluons is a forefront question in modern science. High-energy collisions of heavy nuclei provide a unique opportunity to recreate, for a short moment, the primordial medium of the Big Bang in the laboratory. It is a formidable challenge to infer the properties of this medium from its decay products observed in large detectors. The PI will develop theoretical tools to diagnose this matter and rigorously interpret the experimental data. The PI will continue to build a thriving graduate research program and foster scientific outreach to regional high school students through the Saturday Morning Physics program. This project aims at quantifying fundamental transport properties of the quark-gluon plasma (QGP) and how hadron masses emerge in the quark-to-hadron transition. The transport of heavy quarks through the QGP will be evaluated using innovative quantum many-body techniques, where the heavy-quark interactions will be based on first-principles computations of lattice discretized Quantum Chromodynamics (QCD), the fundamental theory of the strong interaction. The resulting heavy-quark transport coefficients will be implemented into state-of-the-art simulations of the fireballs formed in heavy-ion collisions. In addition, electromagnetic radiation from these fireballs will be calculated to determine: (a) the temperature of the medium, and (b) how the masses of hadrons emerge as the QGP cools down. Current and future experimental programs at the Relativistic Heavy-Ion Collider and Large Hadron Collider have a large emphasis on heavy-quark and electromagnetic observables. The advances achieved through this project will provide the theoretical rigor and accuracy required to convert systematic comparisons to precision data into robust knowledge about the primordial QCD medium.