Ab initio theory of light and medium mass nuclei

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Atomic nuclei are quantum many-body systems made by protons and neutrons interacting with forces that originate from the fundamental theory of Quantum Chromo-Dynamics. The exact treatment of nuclei starting from the constituent nucleons and the inter-nucleon interactions among them has been a long-standing goal in nuclear physics. The goal of this project is to develop a predictive ab initio theory of nuclear structure and nuclear reactions for light and medium mass nuclei. Such a theory is needed for understanding of exotic nuclei investigated at rare isotope facilities like ISAC at TRIUMF, for understanding of nuclear reactions important for astrophysics, for understanding of fusion reactions important for the future energy generation as well as for the testing of fundamental symmetries in nuclear processes. At the same time, it provides a feedback on the quality of inter-nucleon iteractions used as input to these calculations and ultimately helps to improve our knowledge of the nucleon-nucleon interaction, and in particular of the still-not-completely-understood three-nucleon interaction. In this proposal, we combine an ab initio nuclear structure approach capable to describe bound states of light nuclei with a microscopic cluster method developed to describe reactions of nuclear clusters. The resulting method provides a unified description of both bound and unbound nuclear states starting from inter-nucleon interactions among protons and neutrons. We will apply this method to improve our understanding of exotic nuclei such as 9He, 11N, or 17C, to describe halo nuclei like 11Be or 11Li. Using state-of-the-art nuclear forces including the three-nucleon interaction, we will calculate rates of nuclear reactions important for astrophysics including 7Be(p,gamma)8B, 3He(4He,gamma)7Be, 2H(alpha,gamma)6Li and 4He(nn,gamma)6He that are difficult or impossible to measure at low energies at which these reactions occur in cosmic environments. We will also investigate fusion reactions such as 3H(d,n)4He and the aneutronic 11B(p,alpha)8Be relevant for future energy generation. We will study beta decay of 6He that is being measured as an important test of physics beyond the Standard Model. We will also contribute to ab initio investigatinos of medium mass nuclei with one of the major goals to improve calculations of the neutrinoless double-beta decay matrix elements. Finally, a long-term goal of this project is the calculation of reactions important for stellar synthesis of 12C and 16O. It is anticipated that the complexity of theoretical understanding of these reactions equires exa-scale computing.