Bulletin of the American Physical Society
2017 Fall Meeting of the APS Division of Nuclear Physics
Volume 62, Number 11
Wednesday–Saturday, October 25–28, 2017; Pittsburgh, Pennsylvania
Session PB: Heavy Ion Reactions and Radioactive Beams |
Hide Abstracts |
Chair: George Perdikakis, Central Michigan University Room: Salon 2 |
Saturday, October 28, 2017 10:30AM - 10:42AM |
PB.00001: Characterizing NZ equilibration in dynamically deformed system at 15, 25, 35 and 45 MeV/nucleon Andrea Jedele Neutron-proton equilibration is sensitive to the asymmetry energy in the nuclear equation of state. The process is governed by the contact time between the colliding nuclei and the gradient of the potential driving the equilibration. Recent work has shown NZ equilibration between the two largest fragments originating from the excited projectile-like fragment (PLF*) follows first-order kinetics in $^{\mathrm{70}}$Zn, $^{\mathrm{64}}$Zn and $^{\mathrm{64}}$Ni symmetric reaction systems at 35 MeV/nucleon. The rate constant extracted was 3 zs$^{\mathrm{-1}}$, corresponding to a mean equilibration lifetime of 0.3 zs. An experiment has been proposed to examine the characteristics of NZ equilibration in $^{\mathrm{40}}$Ca$+^{\mathrm{64,70}}$Zn at 15, 25, 35 and 45 MeV/nucleon with the NIMROD array. [Preview Abstract] |
Saturday, October 28, 2017 10:42AM - 10:54AM |
PB.00002: New Development on Modelling Fluctuations and Fragmentation in Heavy-Ion Collisions Hao Lin, Pawel Danielewicz During heavy-ion collisions (HIC), colliding nuclei form an excited composite system. Instabilities present in the system may deform the shape of the system exotically, leading to a break-up into fragments. Many experimental efforts have been devoted to the nuclear multifragmentation phenomenon, while traditional HIC models, lacking in proper treatment of fluctuations, fall short in explaining it. In view of this, we are developing a new model to implement realistic fluctuations into transport simulation. The new model is motivated by the Brownian motion description of colliding particles. The effects of two-body collisions are recast in one-body diffusion processes. Vastly different dynamical paths are sampled by solving Langevin equations in momentum space. It is the stochastic sampling of dynamical paths that leads to a wide spread of exit channels. In addition, the nucleon degree of freedom is used to enhance the fluctuations. The model has been tested in reactions such as $^{112}$Sn + $^{112}$Sn and $^{58}$Ni + $^{58}$Ni, where reasonable results are yielded. An exploratory comparison on the $^{112}$Sn + $^{112}$Sn reaction at 50MeV/nucleon with two other models, the stochastic mean-field (SMF) and the antisymmetrized molecular dynamics (AMD) models, has also been conducted. [Preview Abstract] |
Saturday, October 28, 2017 10:54AM - 11:06AM |
PB.00003: Correlations within the Non-Equilibrium Green's Function Method Hossein Mahzoon, Pawel Danielewicz Non-equilibrium Green's function (NGF) method is a powerful tool for studying the evolution of quantum many-body systems. Different types of correlations can be systematically incorporated within the formalism. The time evolution of the single-particle Green’s functions is described in terms of the Kadanoff-Baym equations. In the current work I first focus on introducing the correlations in infinite nuclear matter and then in a finite system. Starting from the harmonic oscillator Hamiltonian, by switching on adiabatically mean-field and correlations simultaneously, a well-defined ground state of a correlated system is arrived at within the NGF method. [Preview Abstract] |
Saturday, October 28, 2017 11:06AM - 11:18AM |
PB.00004: Projectile fragmentation studies using F, Ne, and Na isotopes Maria Mazza Projectile fragmentation is one of the techniques used at nuclear science facilities around the world for the production and study of rare isotopes. In the inverse kinematics reaction, a heavy high energy primary beam impinges on a reaction target producing an excited pre-fragment that soon decays - in a time range between $10^{-9}$ and $10^{-21}$ s - by emission of neutrons and gamma rays. The result is a secondary beam of radioactive nuclei suited for each experiment's needs, but the short lifetime of the pre-fragments prevents direct observation. However, an indirect analysis can be conducted from the reaction products. Neutron multiplicities and the excitation energies of the final fragments are in fact related to the pre-fragments produced in the target and this relationship is expected to be enhanced for final fragments with mass number closest to the reacting beam. The experiment was performed at the National Superconducting Cyclotron Laboratory (NSCL), where a $^{32}Mg$ beam at 86 MeV/u was impinged on a $^{9}Be$ reaction target. The MoNA Collaboration measured neutron multiplicities and kinetic energy spectra for neutrons in coincidence with sodium, neon, and fluorine final fragments in order to study the reaction mechanisms in the production of specific pre-fragments. [Preview Abstract] |
Saturday, October 28, 2017 11:18AM - 11:30AM |
PB.00005: Search for unbound nuclides and beam/fragment optics with the MoNA/LISA segmented target at NSCL Paul Gueye, Nathan Frank, Michael Thoennessen, Thomas Redpath A multi-layered Si/Be segmented target consisting of three 700 mg/cm2 thick Be9 slabs and four 140 microns Si detectors was used by the MoNA Collaboration at the National Superconducting Cyclotron Laboratory of Michigan State University to study the O26 lifetime. This target provides unprecedented information on the incident beams and fragments (energy loss and position), thus allowing for better determination of the incident and outgoing energies and momenta of the detected particles compare to previous experiments conducted at this facility. With the availability of a newly developed Geant4 Monte Carlo simulation of the full N2 vault, we will present and discuss the performances of this target. [Preview Abstract] |
Saturday, October 28, 2017 11:30AM - 11:42AM |
PB.00006: Quasi-free Proton Knockout Reactions on the Oxygen Isotopic Chain Leyla Atar, Thomas Aumann, Carlos Bertulani, Stefanos Paschalis It is well known from electron-induced knockout data that the single-particle (SP) strength is reduced to about 60-70\% for stable nuclei in comparison to the independent particle model due to the presence of short- and long-range correlations. This finding has been confirmed by nuclear knockout reactions using stable and exotic beams, however, with a strong dependency on the proton-neutron asymmetry. The observed strong reduction of SP cross sections for the deeply bound valence nucleons in asymmetric nuclei is theoretically not understood. To understand this dependency quantitatively a complementary approach, quasi-free (QF) knockout reactions in inverse kinematics, is introduced. We have performed a systematic study of spectroscopic strength of oxygen isotopes using QF (p,2p) knockout reactions in complete kinematics at the R3B/LAND setup at GSI with secondary beams containing $^{13-24}$O. The oxygen isotopic chain covers a large variation of separ ation energies, which allow a systematic study of SF with respect to isospin asymmetry. We will present results on the (p,2p) cross sections for the entire oxygen isotopic chain obtained from a single experiment. By comparison with the Eikonal reaction theory the SF and reduction factors will be presented. [Preview Abstract] |
Saturday, October 28, 2017 11:42AM - 11:54AM |
PB.00007: Deuteron Coulomb Excitation in Peripheral Collisions with a Heavy Ion Weijie Du, Peng Yin, Yang Li, Guangyao Chen, Wei Zuo, Xingbo Zhao, James P. Vary We develop an {\it ab initio} time-dependent Basis Function (tBF) method to solve non-perturbative and time-dependent problems in non-relativistic quantum mechanics. As a test problem, we apply this method to the Coulomb excitation of a deuteron by an impinging heavy ion. We employ wave functions for the bound and excited states of the deuterium system based on a realistic nucleon-nucleon interaction and study the evolution of the transition probability, the r.m.s. radius and the r.m.s. momentum of the system during the scattering process. The dependencies of these quantities on the external field strength and the bombarding energy are also analyzed and compared to corresponding results obtained from first-order perturbation theory. The time evolution of both the charge and the momentum distributions is shown. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700