Steffen A. Bass
Professor of Physics
Prof. Bass' main area of research is strong interaction theory, in particular the study of highly excited many-body systems governed by the laws of Quantum-Chromo-Dynamics (QCD).
It is believed that shortly after the creation of the universe in the Big Bang the entire universe existed as a hot and dense plasma of fundamental particles that interacted via a single unified force. As the primordial fire ball expanded and consequentially cooled, the four fundamental forces that we observe today became distinct. The relative importance of these four forces, the strong nuclear, weak nuclear, electromagnetic and gravitational force, in shaping the universe varied as the energy-matter density evolved. In this cosmic picture, about a microsecond after the primordial explosion, the universe was in a state called the Quark Gluon Plasma (QGP) in which quarks and gluons, the basic constituents of the strong interaction force, QCD, roamed freely. Due to the rapid expansion of the universe, this plasma went through a phase transition to form hadrons - most importantly nucleons - which constitute the building blocks of matter as we know it today.
It has been only in the last ten years that accelerators have been in operation that give us the capabilities to create the conditions of temperature and density in the laboratory that are favorable for the QGP to exist. The Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory and the accompaniment of detector systems were built specifically to observe and study this phase of matter. Similar studies have recently commenced at the CERN Large Hadron Collider. The experiments at RHIC have discovered a new form of ultra-dense matter with unprecedented properties, a plasma composed of unbound quarks and gluons, that appears to behave as a nearly ``perfect liquid.''
The central problem in the study of the QGP is that its lifetime is so short that only the ashes of its decay (in the form of hadrons) can be detected. In addition, the deconfined quanta of a QGP are not directly observable due to the fundamental confining property of the physical quantum chromodynamics vacuum, i.e. the properties of the underlying quantum-field theory governing its interactions. One of the main tasks in relativistic heavy-ion research is to find clear and unambiguous connections between the transient (quark-gluon) plasma state and the experimentally observable hadronic final state.
Prof. Bass is actively involved in developing models for the dynamics of such highly energetic heavy-ion collisions. His research involves the application of transport theory, statistical mechanics, heavy-ion phenomenology, as well as the fundamental laws of QCD. Only through the application of dynamical models of heavy-ion collisions and the comparison of their predictions with data, may a link be formed between the observable hadronic and leptonic final state of the heavy-ion reaction and the transient deconfined state of quarks and gluons.
REU Site: Undergraduate Research in Nuclear Particle Physics at TUNL and Duke awarded by National Science Foundation (Senior Investigator). 2018 to 2021
Collaborative Research: SI2-SSI: Jet Energy-loss Tomography with a Statistically and Computationally Advanced Program Envelope (JETSCAPE) awarded by National Science Foundation (Principal Investigator). 2016 to 2020
Nuclear Physics at Extreme Energy Density awarded by Department of Energy (Principal Investigator). 2005 to 2020
Support for Xiaojun Yao awarded by (Principal Investigator). 2017 to 2019
Fermi Gases in Bichromatic Superlattices awarded by North Carolina State University (Principal Investigator). 2012 to 2018
Optical Control of Interactions in Non-equilibrium Fermi Gases awarded by North Carolina State University (Principal Investigator). 2016 to 2018
Nuclear Physics at Extreme Energy Density awarded by Department of Energy (Principal Investigator). 2005 to 2018
JET Collaboration awarded by Department of Energy (Co-Principal Investigator). 2010 to 2015
NEARLY PERFECT LIQUIDS 2009: From Quark-Gluon Plasma to Ultra-Cold Atoms awarded by National Science Foundation (Principal Investigator). 2009 to 2010
Hot Quarks 2008 awarded by National Science Foundation (Principal Investigator). 2008 to 2009
Abada, A., et al. “FCC-ee: The Lepton Collider: Future Circular Collider Conceptual Design Report Volume 2.” European Physical Journal: Special Topics, vol. 228, no. 2, June 2019, pp. 261–623. Scopus, doi:10.1140/epjst/e2019-900045-4. Full Text
Abada, A., et al. “FCC Physics Opportunities: Future Circular Collider Conceptual Design Report Volume 1.” European Physical Journal C, vol. 79, no. 6, June 2019. Scopus, doi:10.1140/epjc/s10052-019-6904-3. Full Text
Cao, S., et al. “Toward the determination of heavy-quark transport coefficients in quark-gluon plasma.” Physical Review C, vol. 99, no. 5, May 2019. Scopus, doi:10.1103/PhysRevC.99.054907. Full Text
Yao, X., et al. “Quarkonium production in heavy ion collisions: coupled Boltzmann transport equations.” Nuclear Physics A, vol. 982, Feb. 2019, pp. 755–58. Scopus, doi:10.1016/j.nuclphysa.2018.10.005. Full Text
Moreland, J. S., et al. “Estimating nucleon substructure properties in a unified model of p-Pb and Pb-Pb collisions.” Nuclear Physics A, vol. 982, Feb. 2019, pp. 503–06. Scopus, doi:10.1016/j.nuclphysa.2018.07.011. Full Text
Xu, Y., et al. “Resolving discrepancies in the estimation of heavy quark transport coefficients in relativistic heavy-ion collisions.” Physical Review C, vol. 99, no. 1, Jan. 2019. Scopus, doi:10.1103/PhysRevC.99.014902. Full Text
Ke, W., et al. “Linearized Boltzmann-Langevin model for heavy quark transport in hot and dense QCD matter.” Physical Review C, vol. 98, no. 6, Dec. 2018. Scopus, doi:10.1103/PhysRevC.98.064901. Full Text
Srivastava, DK, Chatterjee, R, and Bass, SA. "Landau-Pomeranchuk-Midgal effect and charm production in pp collisions at energies available at the CERN Large Hadron Collider using the parton cascade model." Physical Review C 98.5 (November 28, 2018). Full Text
Srivastava, D. K., et al. “Transport dynamics of parton interactions in pp collisions at energies available at the CERN Large Hadron Collider.” Physical Review C, vol. 97, no. 6, June 2018. Scopus, doi:10.1103/PhysRevC.97.064910. Full Text
Auvinen, J., et al. “Investigating the collision energy dependence of η/s in the beam energy scan at the BNL Relativistic Heavy Ion Collider using Bayesian statistics.” Physical Review C, vol. 97, no. 4, Apr. 2018. Scopus, doi:10.1103/PhysRevC.97.044905. Full Text
Bluhm, M., et al. “Fluctuating fluid dynamics for the QGP in the LHC and BES era.” Epj Web of Conferences, vol. 171, 2018. Scopus, doi:10.1051/epjconf/201817116004. Full Text
Xu, Y., et al. “A data-drive analysis for heavy quark diffusion coefficient.” Epj Web of Conferences, vol. 171, 2018. Scopus, doi:10.1051/epjconf/201817118001. Full Text
Xu, Y., et al. Data-driven analysis of the temperature dependence of the heavy-quark transport coefficient. Vol. 289–290, 2017, pp. 257–60. Scopus, doi:10.1016/j.nuclphysbps.2017.05.058. Full Text
Ke, W., et al. “Constraints on rapidity-dependent initial conditions from charged particle pseudorapidity densities and correlations at the LHC.” Nuclear and Particle Physics Proceedings, vol. 289–290, 2017, pp. 483–86. Scopus, doi:10.1016/j.nuclphysbps.2017.05.113. Full Text
Auvinen, J., et al. “Multi-strange hadrons and the precision extraction of QGP properties in the RHIC-BES domain.” Journal of Physics: Conference Series, vol. 779, no. 1, 2017. Scopus, doi:10.1088/1742-6596/779/1/012045. Full Text
Bluhm, M., et al. “Behavior of universal critical parameters in the QCD phase diagram.” Journal of Physics: Conference Series, vol. 779, no. 1, 2017. Scopus, doi:10.1088/1742-6596/779/1/012074. Full Text
Nahrgang, M., et al. “Toward the description of fluid dynamical fluctuations in heavy-ion collisions.” Acta Physica Polonica B, Proceedings Supplement, vol. 10, no. 3, 2017, pp. 687–92. Scopus, doi:10.5506/APhysPolBSupp.10.687. Full Text
Moreau, P., et al. “Traces of non-equilibrium dynamics in relativistic heavy-ion collisions.” Proceedings of Science, vol. 2017-August, 2017.
Auvinen, J., et al. “Parameter extractions for RHIC BES using Bayesian statistics.” Proceedings of Science, vol. 2017-August, 2017.