13 research outputs found
Equilibration chronometry
We study neutron-proton equilibration in dynamically deformed atomic nuclei created in nuclear collisions. The two ends of the elongated nucleus are initially dissimilar in compositions and equilibrate on a sub-zeptosecond timescale following ïŹrst-order kinetics. The technique of equilibration chronometry used to obtain this result enables new insight into the nuclear equation of state that governs many nuclear and astrophysical phenomena leading to the origin of the chemical elements
Using Light Charged Particles to Probe the Asymmetry Dependence of the Nuclear Caloric Curve
Recently, we observed a clear dependence of the nuclear caloric curve on
neutron-proton asymmetry through examination of fully
reconstructed equilibrated quasi-projectile sources produced in heavy ion
collisions at E/A = 35 MeV. In the present work, we extend our analysis using
multiple light charged particle probes of the temperature. Temperatures are
extracted with five distinct probes using a kinetic thermometer approach.
Additionally, temperatures are extracted using two probes within a chemical
thermometer approach (Albergo method). All seven measurements show a
significant linear dependence of the source temperature on the source
asymmetry. For the kinetic thermometer, the strength of the asymmetry
dependence varies with the probe particle species in a way which is consistent
with an average emission-time ordering.Comment: 7 pages, 4 figure
Isospin dependence of collective flow in heavy-ion collisions at intermediate energies
Within the framework of an isospin-dependent Boltzmann-Uehling-Uhlenbeck
(BUU) model using initial proton and neutron densities calculated from the
nonlinear relativistic mean-field (RMF) theory, we compare the strength of
transverse collective flow in reactions and
, which have the same mass number but different neutron/proton
ratios. The neutron-rich system () is found to show
significantly stronger negative deflection and consequently has a higher
balance energy, especially in peripheral collisions. NOTE ADDED IN PROOF: The
new phenomenon predicted in this work has just been confirmed by an experiment
done by G.D. Westfall et al. using the NSCL/MSU radioactive beam facility and a
spartan soccer. A paper by R. Pak et al. is submitted to PRL to report the
experimental result.Comment: Latex file, 9 pages, 4 figures availabe upon request; Phys. Rev.
Lett. (June 3, 1996) in pres
Progress in constraining the asymmetry dependence of the nuclear caloric curve
The nuclear equation of state is a basic emergent property of nuclear material. Despite its importance in nuclear physics and astrophysics, aspects of it are still poorly constrained. Our research focuses on answering the question: How does the nuclear caloric curve depend on the neutron-proton asymmetry? We briefly describe our initial observation that increasing neutron-richness leads to lower temperatures. We then discuss the status of our recently executed experiment to independently measure the asymmetry dependence of the caloric curve
Constraints on the symmetry energy and neutron skins from experiments and theory
The symmetry energy contribution to the nuclear equation of state impacts various phenomena in nuclear astrophysics, nuclear structure, and nuclear reactions. Its determination is a key objective of contemporary nuclear physics, with consequences for the understanding of dense matter within neutron stars. We examine the results of laboratory experiments that have provided initial constraints on the nuclear symmetry energy and on its density dependence at and somewhat below normal nuclear matter density. Even though some of these constraints have been derived from properties of nuclei while others have been derived from the nuclear response to electroweak and hadronic probes, within experimental uncertainties-they are consistent with each other. We also examine the most frequently used theoretical models that predict the symmetry energy and its slope parameter. By comparing existing constraints on the symmetry pressure to theories, we demonstrate how contributions of three-body forces, which are essential ingredients in neutron matter models, can be determined. © 2012 American Physical Society.link_to_subscribed_fulltex