Combining Halo-EFT Descriptions of Nuclei and Precise Models of Nuclear Reactions

The clear separation of scales observed in halo nuclei between the extended halo and the compact core makes these exotic nuclei a perfect subject for effective field theory (EFT). Such description leads to a systematic expansion of the core-halo Hamiltonian, which naturally orders the nuclear-structure observables. In this short review, I show the advantages there are to include Halo-EFT descriptions within precise models of reactions. It helps identifying the nuclear-structure observables that matter in the description of the reactions, and enables us to easily bridge predictions of nuclear-structure calculations to reaction observables. I illustrate this on breakup, transfer and knockout reactions with $$^{11}$$ 11 Be, the archetypical one-neutron halo nucleus.

Status and Perspectives of 2ϵ, ϵβ+ and 2β+ Decays

This paper reviews the main experimental techniques and the most significant results in the searches for the 2ϵ, ϵβ+ and 2β+ decay modes. Efforts related to the study of these decay modes are important, since they can potentially offer complementary information with respect to the cases of 2β− decays, which allow a better constraint of models for the nuclear structure calculations. Some positive results that have been claimed will be mentioned, and some new perspectives will be addressed shortly.

Electron Capture in Nuclear Structure and Astrophysics

Electron capture on nucleons and nuclei, is one of the most important weak interaction processes in the dynamics and evolution of massive stars. Especially on nuclei of the Fe mass region the role of e− capture is crucial in the phase of stellar core collapse. Furthermore, a realistic treatment of electron capture on heavy nuclei provides signi cant information in the hydrodynamics of core collapse and bounce. In this work, we exploit the advantages of a recently published numerical approach to perform nuclear structure calculations of the electron capture in F e group nuclear isotopes. As a rst concrete example, which is simultaneously o ering a good test of ourmethod,wechoosethereaction56Fe(e−,νe)56Mn* that plays a decisive role in core collapse supernovae. We also improve the previous formalism by constructing compact analytical expressions for the required reduced matrix elements of all basic multipole operators in isospin representation. Such a compact formalism o ers the advantage of performing state-by-state calculations of the transition rates for semi- leptonic nuclear processes through advantageous computer codes written in isospin representation.

Studying supernova neutrinos through nuclear structure calculations

Differential and integrated cross section calculations are performed in the context of the quasi particle random phase approximation (QRPA) by utilizing realistic two- nucleon forces, for the 64,66 Zn isotopes, contents of the COBRA double beta decay detector. For these isotopes the response to supernova neutrinos is of current inter- est. The response of the 66 Zn isotope to the energy-spectra of supernova neutrinos is also explored by convoluting the original results for the differential cross sections by employing: (i) a two-parameter Fermi-Dirac (FD) and (ii) a Power-Law (PL) neutrino energy distribution. Such folded cross sections are useful in low-energy astrophysical-neutrino detection in underground terrestrial experiments.

Accelerating many-nucleon basis generation for high performance computing enabled ab initio nuclear structure studies

We present the problem of generating a many-nucleon basis in [Formula: see text]-scheme for ab initio nuclear structure calculations in a symmetry-adapted no-core shell model framework. We first discuss and analyze the basis construction algorithm whose baseline implementation quickly becomes a significant bottleneck for large model spaces and heavier nuclei. The outcomes of this analysis are utilized to propose a new scalable version of the algorithm. Its performance is consequently studied empirically using the Blue Waters supercomputer. The measurements show significant acceleration achieved with over two orders of magnitude speedups realized for larger model spaces.

Electron-capture modes with realistic nuclear structure calculations

Nuclear electron capture posses prominent position among other weak interaction processes occuring in explosive nucleosynthesis. In particular, this process plays important role in the core-colapse of massive stars by modifying the electron to baryon ratio Ye. From a nuclear theory point of view, such processes may be studied by using the same nuclear methods (e.g. the quasi-particle random phase approximation, QRPA), employed in the present work with these used for the one-body charge changing nuclear reactions (β-decay modes, charged-current electron-neutrino absorption by nuclei, etc). In this work we calculate e−-capture cross sections on 56Fe using two different approaches. At first, original cross section calculations are perfored by using the pn-QRPA method considering all the accessible transitions of the final nucleus 56Mn. Secondly, we evaluate the Gamow-Teller strength distributions and obtain the cross sections at the limit of zero-momentum transfer. The agreement between the two methods is very good.