Halo World: The Story of Nuclear Halos and the Efimov Effect

ABSTRACT: 
The advancement in the production of energetic radioactive ion beams (RIB) has opened up new vistas in contemporary nuclear physics. On one hand it provides the means to explore the structural properties and reaction dynamics of nuclei near the drip lines. On the other hand some of the light, neutron-rich nuclei with their 2-neutron halo structure, characterized by large spatial extension and very low separation energy of the neutrons, have emerged as ideal candidates to search for exotic quantum mechanical effects, like the Efimov Effect.

The first part of this talk will be devoted to an introduction to the discovery of halo nuclei and the global efforts in this direction. This will be followed by a brief overview of the different theoretical approaches with particular emphasis on a three-body model to understand the key structural properties of 2-neutron halo nuclei. 2-neutron halo nuclei are the ideal candidates to search for the Efimov states in atomic nuclei. I shall briefly introduce the Efimov effect and its universal features in three-body systems. This will be followed by a discussion on our search for Efimov states, within the framework of our model calculations, in 2n-halo nuclei, like, 14Be, 19B,20,22C etc. We shall discuss the important finding of the evolution of bound Efimov states into resonances. It will be argued that the evolution of the bound Efimov states into asymmmetric resonances, because of the underlying Fano mechanism, takes us closer to the possible experimental observation of Efimov effect in atomic nuclei.