Abstract: Where and how multinucleon halos form in exotic nuclei is key to understanding nuclear structure at the limits of existence. The nature and presence of halo structures are intrinsically linked to deformation and shell evolution, and the possibility of dineutron correlations in neutron-rich matter.
Little is known about the heaviest bound isotope of boron, 19B. It is known to be bound with a very low two neutron separation energy and an enhanced interaction cross-section, making it a possible 2n Borromean halo nucleus. However, being also weakly bound to four neutron removal, 19B might also have a 4n halo or have a neutron skin.
I will present results of an experiment using the SAMURAI setup at RIKEN RIBF, where we performed exclusive measurements of the Coulomb dissociation of 19B into 17B and two neutrons in collisions with lead at 220 MeV/nucleon to extract the electric dipole transition strength B(E1), and thus information on the halo structure of 19B. Through comparison to theoretical calculations, I will discuss signatures of dineutron correlations our experimental results.