Narrow Results

It is now known that in neutron-rich nuclei, old magic numbers disappear and new ones appear. Single nucleon and double nucleon separation energies are plotted here in all possible manner. Using this data it is shown here that nuclei with pair of proton number Z and neutron number N(Z,N): (6, 12), (8, 16), (10, 20), (11, 22) and (12, 24) exhibit exceptional stability or magicity. As such these magic numbers appear in pairs. This correlation is shown here to be indicative of predominance of tritons in the ground state of these neutron-rich nuclei. Thus has the structure of 10 in the ground state. It is shown here that this is due to fundamental symmetry arguments based on a new symmetry group nusospin.

In a decade-and-a-half old experiment, Raabe et al. [Nature 431, 823 (2004)], had studied fusion of an incoming beam of halo nucleus ⁶He with the target nucleus ${}^{238}U$. We extract a new interpretation of the experiment, different from the one that has been inferred so far. We show that their experiment is actually able to discriminate between the structures of the target nucleus (behaving as standard nucleus with density distribution described with canonical RMS radius $r=r_0{A}^{\frac{1}{3}}$ with $r_0=1.2$ fm), and the “core” of the halo nucleus, which surprisingly, does not follow the standard density distribution with the above RMS radius. In fact, the core has the structure of a tennis-ball (bubble)-like nucleus, with a “hole” at the center of the density distribution. This novel interpretation of the fusion experiment provides an unambiguous support to an almost two decades old model [A. Abbas, Mod. Phys. Lett. A16, 755 (2001)], of the halo nuclei. This Quantum Chromodynamics based model succeeds in identifying all known halo nuclei and makes clear-cut and unique predictions for new and heavier halo nuclei. This model supports the existence of tennis-ball (bubble)-like core, of even the giant-neutron halo nuclei. This should prove beneficial to the experimentalists, to go forward more confidently, in their study of exotic nuclei.

The idea of treating the trinucleon systems as elementary entities in the elementary particle model (EPM) as an Effective Field Theory has been a success in explaining the weak charge-changing processes in nuclei. The EPM results are found to be as good as those obtained from nuclear microscopic models using two-and three-body forces. We extend this concept to investigate the validity of the elemental nature of $A=3$ nuclei through studies of nuclear structure of neutron-rich nuclei. By treating neutron-rich nuclei as primarily made up of tritons as its building blocks, we extract one- and two-triton separation energies of these nuclei. Calculations have been performed here within relativistic mean field (RMF) models with latest interactions. Clear evidence arises of a new shell structure with well-defined predictions of new magic nuclei. These unique predictions have been consolidated by standard one- and two-neutron separation energy calculations. The binding energy per nucleon plots of these nuclei also confirm these predictions. We make unambiguous prediction of six magic nuclei: ${}_8^{24}{\mathrm{\text{O}}}_{16}$, ${}_{20}^{60}{\mathrm{\text{Ca}}}_{40}$, ${}_{35}^{105}{\mathrm{\text{Br}}}_{70}$, ${}_{41}^{123}{\mathrm{\text{Nb}}}_{82}$, ${}_{63}^{189}{\mathrm{\text{Eu}}}_{126}$ and ${}_{92}^{276}{\mathrm{\text{U}}}_{184}$.