Steffen A. Bass

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

Nuclear Physics at Extreme Energy Density awarded by Department of Energy (Principal Investigator). 2005 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

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


Srivastava, DK, Bass, SA, and Chatterjee, R. "Production of charm quarks in a parton cascade model for relativistic heavy ion collisions at s NN =200 GeV." Physical Review C 96.6 (December 27, 2017). Full Text

Moreland, JS, Bernhard, JE, Ke, W, and Bass, SA. "Flow in small and large quark-gluon plasma droplets: the role of nucleon substructure." Nuclear Physics A 967 (November 2017): 361-364. Full Text

Bernhard, JE, Moreland, JS, and Bass, SA. "Characterization of the initial state and QGP medium from a combined Bayesian analysis of LHC data at 2.76 and 5.02 TeV." Nuclear Physics A 967 (November 2017): 293-296. Full Text

Bass, SA, Bernhard, J, and Moreland, JS. "Determination of Quark-Gluon-Plasma Parameters from a Global Bayesian Analysis." Nuclear Physics A 967 (November 2017): 67-73. Full Text

Auvinen, J, Karpenko, I, Bernhard, JE, and Bass, SA. "Revealing the collision energy dependence of η / s in RHIC-BES Au+Au collisions using Bayesian statistics." Nuclear Physics A 967 (November 2017): 784-787. Full Text

Nahrgang, M, Bluhm, M, Schäfer, T, and Bass, SA. "Baryon number diffusion with critical fluctuations." Nuclear Physics A 967 (November 2017): 824-827. Full Text

Xu, Y, Nahrgang, M, Bernhard, JE, Cao, S, and Bass, SA. "A data-driven analysis of the heavy quark transport coefficient." Nuclear Physics A 967 (November 2017): 668-671. Full Text

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


Bluhm, M, Nahrgang, M, Schäfer, T, and Bass, SA. "Fluctuating fluid dynamics for the QGP in the LHC and BES era." February 2, 2018. Full Text

Xu, Y, Nahrgang, M, Cao, S, Bernhard, JE, and Bass, SA. "A data-drive analysis for heavy quark diffusion coefficient." February 2, 2018. Full Text

Auvinen, J, Bernhard, JE, and Bass, SA. "Systematic extraction of QGP properties." January 1, 2017. 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

Nahrgang, M, Bluhm, M, Schäfer, T, and Bass, S. "Toward the description of fluid dynamical fluctuations in heavy-ion collisions." January 1, 2017. Full Text

Hao, L, Healey, CG, Bass, SA, and Yu, HY. "Visualizing static ensembles for effective shape and data comparison." January 1, 2016.

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