Seminars

Wednesday, Dec 07 at 11:00 AM
1200 FRIB Laboratory
Linda Hlophe, Lawrence Livermore National Laboratory
Towards a predictive description of direct nuclear reactions

Abstract:  Nuclear reactions play a critical role in probing the properties of atomic nuclei, production of elements in astrophysical environments, as well as national security applications. For example, a class of reactions known as ‘transfer reactions’ are useful in determining spins, parities, and spectroscopic factors for specific nuclear states. In particular, deuteron-induced transfer reactions on rare isotopes have been used to probe single-particle levels of nuclei as well as to indirectly infer neutron-capture rates needed to simulate the synthesis of heavy elements in cataclysmic astrophysical events. Since the observables measured in reaction experiments are cross sections, extracting structure properties as well as the relevant neutron-capture rates requires a reliable reaction theory. In light of reaction measurements taking place in rare isotope facilities around the world and in anticipation of the large influx of data from FRIB, theories that are suitable for the description of reactions involving exotic nuclei are needed. Using the example of deuteron-induced reactions, I will discuss the importance of a dependable reaction theory for translating experimental measurements into the desired nuclear information. I will also discuss advances in the three-body (neutron + proton + nucleus) description of such reactions as well as ab initio approaches that seek a solution of the many-body scattering problem, starting from nucleon-nucleon potentials derived from chiral effective field theory. Finally, I will give my perspective on efforts to construct predictive reaction theories that can be reliably applied to nuclei closer to the dripline by focusing on integrating few-body reaction dynamics with ab initio methods.

Thursday, Dec 08 at 11:00 AM
1200 FRIB Laboratory
Grigor Sargsyan, Lawrence Livermore National Laboratory
Charge-exchange Processes from Ab initio Modeling

Abstract:  Ab initio models are built upon realistic internucleon interactions, which empowers them with predictive capability. The ab initio symmetry-adapted no-core shell model (SA-NCSM) utilizes emergent symmetries in nuclei to reduce the dimensionality of the model space. This, in turn, allows one to reproduce the low-energy nuclear dynamics with only a small fraction of the model space, hence making solutions to heavier nuclei and ultralarge model spaces feasible. This work discusses calculations of beta decays and nucleon-nucleus spectroscopic overlaps using the SA-NCSM. I will further discus how these calculations can be utilized in construction of nuclear structure-based optical potentials vital for the studies of reactions involving rare isotopes.

Friday, Dec 09 at 11:00 AM
1200 FRIB Laboratory
Zhonghao Sun, Oak Ridge National Laboratory
Precise and reliable calculations of exotic nuclei

Abstract:  Precise and predictive calculations of the atomic nuclei from realistic nuclear force can help us to explain the exotic nuclear phenomena, understand the fundamental theory, explore the limit of stability, and study the state of the neutron star. The advances in computational power, emerging machine learning technology, and the development of many-body methods make it possible to perform uncertainty quantification and sensitivity analyses in nuclear structure calculations. It can help us to understand how the fundamental interaction leads to the emergence of various exotic phenomena observed from the facility of rare isotope beams and provide essential input for future experiment design. In this talk, I will report on the progress of the ab-initio coupled-cluster method in describing spherical and deformed atomic nuclei. I will also introduce the quantified predictions of the neutron skin thickness of 208Pb and the drip line of oxygen isotopes."