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One neutron triaxial halo candidates in aluminum isotopes from reaction observables

Jia-Lin An, Shi-Sheng Zhang, Kaiyuan Zhang

Abstract

Microscopic description of one neutron ($1n$) halo candidates $^{40,42}$Al, with particular triaxial shape, is presented by combining the triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc) with the Glauber reaction model for the first time. In this scheme, the reaction cross sections of aluminum isotopes on a carbon target at 240 and 900 MeV/A are calculated, which exhibit a pronounced increase for $^{40,42}$Al + $^{12}$C deviating from the systematic trend of their neighbours. Furthermore, the predicted longitudinal momentum distributions of the residues after $1n$ removal reactions for $^{40,42}$Al + $^{12}$C are narrower than those for $^{36,38}$Al + $^{12}$C, which suggest halo structure with spatially extended density distribution. Based on the large occupation probabilities of $p$-wave valence neutrons, we identify $^{40,42}$Al as the first triaxially deformed $1n$ $p$-wave halo candidates. This work cast a new light on the search for the heavier halo nuclei for future experiments in the mass region of $A\approx40$, through theoretical predictions from triaxial structure to reaction observables.

One neutron triaxial halo candidates in aluminum isotopes from reaction observables

Abstract

Microscopic description of one neutron () halo candidates Al, with particular triaxial shape, is presented by combining the triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc) with the Glauber reaction model for the first time. In this scheme, the reaction cross sections of aluminum isotopes on a carbon target at 240 and 900 MeV/A are calculated, which exhibit a pronounced increase for Al + C deviating from the systematic trend of their neighbours. Furthermore, the predicted longitudinal momentum distributions of the residues after removal reactions for Al + C are narrower than those for Al + C, which suggest halo structure with spatially extended density distribution. Based on the large occupation probabilities of -wave valence neutrons, we identify Al as the first triaxially deformed -wave halo candidates. This work cast a new light on the search for the heavier halo nuclei for future experiments in the mass region of , through theoretical predictions from triaxial structure to reaction observables.

Paper Structure

This paper contains 4 sections, 3 equations, 2 figures, 1 table.

Table of Contents

  1. Introduction
  2. Theoretical Framework
  3. Reaction observables for neutron-rich aluminum isotopes on a carbon target
  4. Summary

Figures (2)

  • Figure 1: (Color online) RCSs $\sigma_R$ of aluminum isotopes on a carbon target at 240 and 900 MeV/A, respectively. The open black circles denote the cross sections calculated with the Glauber model with inputs from the TRHBc theory. The gray dashed line represents a fit to the cross sections of $^{31-39}$Al + $^{12}$C.
  • Figure 2: (Color online) (a) Inclusive longitudinal momentum distributions d$\sigma/$d$\bm{p}_{\parallel}$ [mb/(MeV/c)] of residues after the break-up reactions $^{36,38,40,42}$Al + $^{12}$C at the incident energies (a) 240 MeV/A, (b) 900 MeV/A, respectively. The red/black/blue/green solid line refers to the predictions for $^{42}$Al/$^{40}$Al/$^{38}$Al/$^{36}$Al + $^{12}$C using the TRHBc + Glauber approach.