Abigail Bickley
Nuclear Equation of State
(Research Description PDF - 1107 kb)My research interests revolve around studying the properties of nuclear matter over a wide range of temperatures and energy densities. The relationship between the environmental conditions a nucleus is subjected to and the properties it exhibits is governed by the equation of state of nuclear matter. The equation of state not only characterizes the properties of nuclear matter, but also provides a mathematical relationship between the thermodynamic variables used to characterize nuclei. This relationship governs the physical characteristics and behavior of nuclear matter as it existed in the early universe, in neutron stars, and in terrestrial nuclear matter. Within a nucleus, the binding energy per nucleon receives contributions from the energy of symmetric nuclear matter and a correction term related to the neutron-proton asymmetry known as the symmetry energy. The asymmetry correction accounts for isospin differences resulting from an inequality in the numbers of protons and neutrons in the nucleus. The Chart of the Nuclides demonstrates that the majority of the known nuclei contain more neutrons than protons, thus it is important to understand how the isospin asymmetry influences the energy of the nucleus. Furthermore, to understand and predict the behavior of nuclear matter exposed to different environmental conditions the symmetry energy must be constrained. Of particular interest is the density dependence of the nuclear equation of state, which has wide ranging effects on the properties of neutron-rich nuclei, the structure of neutron stars and the dynamics of supernova collapse. Theoretical calculations predict a wide variety of different forms for the dependence of the symmetry energy on the density of the system. Recent experimental results have placed preliminary constraints on the symmetry energy for densities less than that of normal nuclear matter, but experimental data do not exist for supra-normal densities.
In the laboratory setting, collisions of heavy nuclei allow the density of the system to be controlled and provide a window through which we can observe the properties of the nucleus. The particles produced in the collision of asymmetric nuclei provide constraints on our understanding of the symmetry energy term of the nuclear equation of state. This serves to further our understanding of the properties of neutron-rich nuclei, which dominate the chart of the known nuclides. Collisions of heavy ions are performed and observed at National Superconducting Cyclotron Laboratory (NSCL), which is adjacent to the Chemistry Department. The facilities available at NSCL provide a unique opportunity for studying the symmetry energy through the collision of isospin asymmetric heavy ions due to the wide variety of exotic beams and targets available. In these collisions, densities regimes ranging from 0.5-1.7 times that of normal nuclear matter can be studied. These capabilities allow constraints to be made to the nuclear equation of state that are vital to the advancement of understanding of astrophysical processes related to neutron stars and supernova explosions and to the understanding of nuclear structure away from the valley of stability
Selected Publications
Cold Nuclear Matter Effects on J/Psi Production as Constrained by Deuteron-Gold Measurements at sqrt(s_NN) = 200 GeV, A. Adare et al., Phys. Rev. C 2008, 77, 024912.Quarkonium Production in PHENIX, A. Bickley for the PHENIX Collaboration, Nucl. Phys. 2007, A783, 285.
J/Psi Production vs. Centrality, Transverse Momentum, and Rapidity in Au+Au Collisions at sqrt(s_NN) = 200 GeV, A. Adare, et al., Phys. Rev. Lett. 2007, 98, 232201.
J/Psi Production vs. Transverse Momentum and Rapidity in p+p Collisions at sqrt(s) = 200 GeV, A. Adare et al., Phys. Rev. Lett. 2007, 98, 232002.
Charged Antiparticle to Particle Ratios Near Midrapidity in p+p Collisions at sqrt(s_NN) = 200 GeV, B.B. Back, et al., Phys. Rev. C71 2005, 021901(R).
Centrality Dependence of Charged Hadron Transverse Momentum Spectra in Au+Au Collisions from sqrt(s_NN) = 62.4 to 200 GeV, B.B. Back et al., Phys. Rev. Lett. 2005, 94, 082304.
Centrality Dependence of Charged Antiparticle to Particle Ratios Near Mid-Rapidity in d+Au Collisions at sqrt(s_NN) = 200 GeV, B.B. Back et al., Phys. Rev. C70 2004, 011901(R).
