Steffen A. Bass

Professor of Physics

Office Location: 
261D Physics, Durham, NC 27708
Front Office Address: 
Box 90305, Durham, NC 27708-0305
(919) 660-2479


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.

Education & Training

  • Ph.D., Johann Wolfgang Goeth Universitat Frankfurt Am Main (Germany) 1997

  • M.S., Johann Wolfgang Goeth Universitat Frankfurt Am Main (Germany) 1993

Selected Grants

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

Support for Xiaojun Yao awarded by Brookhaven National Labs (Principal Investigator). 2017 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

Modeling and Analysis of Ultra-Realistic Heavy-Ion Collisions awarded by Department of Energy (Principal Investigator). 2003 to 2008

Probing the QCD Equation of State and Hadronization at RHIC awarded by National Science Foundation (Principal Investigator). 2003 to 2007


Cao, S, Park, C, Barbieri, RA, Bass, SA, Bazow, D, Bernhard, J, Coleman, J, Fries, R, Gale, C, He, Y, Heinz, U, Jacak, BV, Jacobs, PM, Jeon, S, Kordell, M, Kumar, A, Luo, T, Majumder, A, Nejahi, Y, Pablos, D, Pang, L-G, Putschke, JH, Roland, G, Rose, S, Schenke, B, Schwiebert, L, Shen, C, Sirimanna, C, Soltz, RA, Velicanu, D, Vujanovic, G, Wang, X-N, and Wolpert, RL. "Multistage Monte Carlo simulation of jet modification in a static medium." Physical Review C 96.2 (August 2017). Full Text

Xu, Y, Moreau, P, Song, T, Nahrgang, M, Bass, SA, and Bratkovskaya, E. "Traces of nonequilibrium dynamics in relativistic heavy-ion collisions." Physical Review C 96.2 (August 2017). Full Text

Aarts, G, Aichelin, J, Allton, C, Arnaldi, R, Bass, SA, Bedda, C, Brambilla, N, Bratkovskaya, E, Braun-Munzinger, P, Bruno, GE, Dahms, T, Das, SK, Dembinski, H, Djordjevic, M, Ferreiro, E, Frawley, A, Gossiaux, P-B, Granier de Cassagnac, R, Grelli, A, He, M, Horowitz, WA, Innocenti, GM, Jo, M, Kaczmarek, O, Kuijer, PG, Laine, M, Lombardo, MP, Mischke, A, Munhoz, MG, Nahrgang, M, Nguyen, M, Oliveira da Silva, AC, Petreczky, P, Rothkopf, A, Schmelling, M, Scomparin, E, Song, T, and Stachel, J et al. "Heavy-flavor production and medium properties in high-energy nuclear collisions --What next?." The European Physical Journal A 53.5 (May 2017). Full Text

Bluhm, M, Nahrgang, M, Bass, SA, and Schäfer, T. "Impact of resonance decays on critical point signals in net-proton fluctuations." The European Physical Journal C 77.4 (April 2017). Full Text

Cao, S, Qin, G-Y, and Bass, SA. "Suppression and Two-Particle Correlations of Heavy Mesons in Heavy-Ion Collisions." Nuclear Physics A 956 (December 2016): 505-508. Full Text

Xu, Y, Cao, S, Nahrgang, M, Ke, W, Qin, G-Y, Auvinen, J, and Bass, SA. "Heavy-flavor dynamics in relativistic p-Pb collisions at sNN=5.02 TeV." Nuclear and Particle Physics Proceedings 276-278 (July 2016): 225-228. Full Text

Shen, C, Qiu, Z, Song, H, Bernhard, J, Bass, S, and Heinz, U. "The iEBE-VISHNU code package for relativistic heavy-ion collisions." Computer Physics Communications 199 (February 2016): 61-85. Full Text

Hao, L, Healey, CG, and Bass, SA. "Effective Visualization of Temporal Ensembles." IEEE Transactions on Visualization and Computer Graphics 22.1 (January 31, 2016): 787-796. Full Text

Cao, S, Huang, Y, Qin, G-Y, and Bass, SA. "The influence of initial state fluctuations on heavy quark energy loss in relativistic heavy-ion collisions." Journal of Physics G: Nuclear and Particle Physics 42.12 (December 1, 2015): 125104-125104. Full Text


Bluhm, M, Nahrgang, M, Bass, SA, and Schäfer, T. "Behavior of universal critical parameters in the QCD phase diagram." January 2017. Full Text

Bass, SA, Fries, RJ, Nonaka, C, and Muller, B. "Hadronization at RHIC: Interplay of recombination and fragmentation." 2005.

Bass, SA, Dumitru, A, Danielewicz, P, and Pratt, S. "Probing hadronization with strangeness." 2001.

Bass, SA, Soff, S, Belkacem, M, Brandstetter, M, Bleicher, M, Gerland, L, Konopka, J, Neise, L, Spieles, C, Weber, H, Stocker, H, and Greiner, W. "Hadrochemical vs. microscopic analysis of particle production and freeze-out in ultrarelativistic heavy ion collisions." 1998.