Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session Q05: Frontiers of Few-body Nuclear DynamicsInvited Live Streamed
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Sponsoring Units: DNP GFB Chair: Sofia Quaglioni, Lawrence Livermore Natl Lab Room: Astor |
Monday, April 11, 2022 10:45AM - 11:21AM |
Q05.00001: Searches for Two-Neutron Halos in Light and Medium-Mass Nuclei Invited Speaker: Rituparna Kanungo
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Monday, April 11, 2022 11:21AM - 11:57AM |
Q05.00002: First-Principle Calculations of Astrophysical Reactions Invited Speaker: Konstantinos Kravvaris The ability to accurately predict light-ion reaction cross sections is key to a wide range of applications ranging from the modeling of stellar interiors to the measurement of actinide fission properties. Many such reactions remain inaccessible to experimental efforts due to, for example, the low energies at which they take place, leading to reduced reaction rates. A first-principle theory of nuclear reactions combined with an efficient computational capability to calculate their cross sections may provide accurate predictions for these reactions and can assist in providing accredited nuclear data in support of a wide range of nuclear security applications. However, due to the need for high-precision predictions, it is also imperative to provide quantified estimates for calculation uncertainties. In this talk I will outline the basics of the no-core shell model with continuum first-principle approach to light-ion reactions, demonstrate its applicability in cases relevant to astrophysics and applications, and discuss currently ongoing efforts for quantifying theoretical uncertainties. |
Monday, April 11, 2022 11:57AM - 12:33PM |
Q05.00003: Universality in The Three- and Four-Neutron Systems Invited Speaker: Chris H Greene This talk addresses the question of whether low energy bound or resonant states can possibly exist for a system of only three or four neutrons. Our exploration was trigged by an experiment published by Kisamori et al. [[Phys. Rev. Lett. 116, 052501 (2016)] which found an excess of low energy tetraneutron events in the nuclear reaction 8He+4He-->8Be+4n. Prior to our work, a number of theoretical explorations were carried out, with several concluding that a tetraneutron resonance can emerge from solving the 4n Schroedinger equation with known nucleon-nucleon interaction potentials, and a comparable number of studies concluding that no tetraneutron resonance or bound state is possible. Stimulated by these experimental and theoretical efforts, we have investigated this question using a theoretical technique with a well-proven track record for predicting resonances: the adiabatic hyperspherical coordinate framework. The result of our calculations, after solving the Schroedinger equation in that framework, using a standard nuclear interaction Hamiltonian that either includes or neglects 3-body interactions, are a set of adiabatic potential curves. Inspection of those potential curves makes it immediately and intuitively clear that no tetraneutron and no trineutron resonance can possibly exist. Analysis of scattering phaseshifts in our treatment confirms the absence of any resonance, but it does indicate a possible interpretation of the unexpectedly large number of four neutron events at low energy (below 3 MeV) in the Kisamori et al. experiment. Specifically we show that, consistent with 4-body universality studies, there is a long range attractive 4-body hyperradial potential proportional the inverse of the hyperradius cubed, which causes the 4n density of states to diverge at zero energy. Accordingly, we conjecture that this divergent but nonresonant density of states is responsible for the excess low energy 4n events seen experimentally. |
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