Description of reactions involving halo nuclei: using effective field theory to compute cross sections from ab initio predictions

Pierre Capel, Institute for Nuclear Physics, Johannes Gutenberg University Mainz
Wednesday, Apr 18, 4:10 PM - Nuclear Science Seminar
1200 FRIB Laboratory

Abstract:  Halo nuclei are radioactive nuclei, which exhibit an uncommon nuclear structure: their matter radius is much larger than that of stable nuclei. This large size is qualitatively understood as due to their low separation energy for one or two neutrons. Thanks to this loose binding, these valence neutrons exhibit a high probability of presence at a large distance from the other nucleons. They thus form a sort of diffuse halo around a compact core. The best known examples are 11Be, with a one-neutron halo, and 11Li, with a two-neutron halo. Due to their short lifetime, these nuclei are mostly studied at RIB facilities through reactions, like breakup. In order to extract valuable structure information from measured cross sections, a precise model of the collision coupled to a reliable description of the projectile is needed. Many such models have been developed for breakup. However, they mostly rely on a simple two- or three-body description of the nucleus. Recently, 11Be has become accessible to ab initio calculations. Unfortunately, such an A-body description is too computationally demanding to be directly included within existing reaction models. During this seminar, I will explain how we can use the Halo effective field theory to constrain the description of halo nuclei within a reliable breakup model from the outputs of ab initio calculations. The results obtained for the breakup of 11Be on Pb and C at 70AMeV are in excellent agreement with experimental measurements. This not only proves the feasibility of incorporating predictions from ab initio calculations in reaction theory, but, more importantly, they confirm the results for important aspects of the structure of 11Beobtained by the ab initio calculation of Calci et al.