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Ralf Rapp


Ralf Rapp


Prof. Ralf Rapp received his PhD in 1996 from the University of Bonn (Germany); he did a postdoc at SUNY Stony Brook (1996-1999), held research assistant professor positions in Stony Brook (2001-2002) and at NORDITA (Copenhagen, 2002-2003), joined Texas A&M as assistant professor (2003), and subsequently became associate (2006) and full professor (2010). Prof. Rapp and his group conduct theoretical studies of spectral and transport properties of hadrons in hadronic matter and quarks in the Quark-Gluon Plasma (QGP), their relations to QCD phase transitions and observable signatures in heavy-ion collisions. They are also interested in color-superconducting cold dense quark matter and associated signatures in observables from compact ("neutron") stars, including mechanisms for gamma ray bursters. 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. Prof. Rapp and collaborators are developing theoretical tools to diagnose this matter and rigorously interpret the experimental data. He continues to build a thriving graduate research program and to foster scientific outreach to regional high school students through the Saturday Morning Physics program. The projects aim at quantifying fundamental transport properties of the 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.

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