The article on 2n-decay of the unbound ¹⁶Be nucleus has been published, showing the importance of genuine three-body dynamics for the relative-energy distributions of the fragments.

The mathematical derivation to solve inhomogeneous equation for the decay of 2n emitters has been accomplished. 

The method involves the calculation of a source term that takes into account all interactions, starting from a characteristic resonance eigenstate (based on previous work: PRC 99 (2019) 014604 ).

The implementation of the equations in a computer code has been finished, and collaboration with experimental group to study ¹⁶Be data is ongoing. A publication is in preparation.

The work on dineutron correlations at the surface of Borromean nuclei has been published. The role played by the core is established and calls for further studies.

For the first time, the effect of the core is studied by analyzing the opening angle as a function of the intrinsic neutron momentum in knockout reactions from Borromean two-neutron halo nuclei.

Together with A. Corsi (SAMURAI18 collaboration), the role played by the core in developing dineutron correlations has been explored by the researcher J. Casal and his co-worker M. Gómez-Ramos. Calculations and data for 11Li, 14Be and 19B provide the first strong evidence that such correlations appear as a universal feature at the surface of the nucleus, as suggested by previous works. In the case of 14Be, core excitations tend to reduce the dineutron correlation signal, which may be crucial to understand this phenomenon for heavier halo nuclei. 

The mathematical derivation of the coupling potentials within the four-body CDCC calculations including core excitations has been accomplished.

Closed expressions in the general case and within a no-recoil approximation have been obtained. The former involves a complicated scheme arising from a series of multiple expansions, and requires matrix elements of the deformed potentials between coupled states. The latter provides a much simpler approach, where the key ingredient are the deformed core-target potential and the hyperradial overlap integrals between wave-function components for different core states.

The implementation of the equations in a computer code is ongoing. First preliminary results will be soon available.

The researcher J. Casal publishes, in collaboration with Dr. Gómez-Ramos, a theoretical work on opening angle and dineutron correlations in proton-target knockout reactions with Borromean halo nuclei, applying state-of-the art methods to the paradigmatic 11Li case.  The study provides a link between structure properties and reaction observables, suggesting that the relevant information can only be extracted from the data at small intrinsic momenta. 

Extensions to include core excitations in the coupled-channels description of these processes is underway to support the analysis of yet unpublished 14Be data, in clear alignment with the SENUC goals.