Halo Nuclei Research Articles

Influence of Nuclear Potential Diffuseness on the Neutron Halo Structure in Zr Isotopes near the Neutron Drip Line

Influence of Nuclear Potential Diffuseness on the Neutron Halo Structure in Zr Isotopes near the Neutron Drip Line

Three-body calculations of β decay applied to Li11

A novel practical few-body method is formulated to include isospin symmetry for nuclear halo structures. The method is designed to describe $\ensuremath{\beta}$ decay, where the basic concept of isospin symmetry facilitates a proper understanding. Both isobaric analog and antianalog states are treated. We derive general and explicit formulas for three-body systems using hyperspherical coordinates. The example of the $\ensuremath{\beta}$ decaying $^{11}\mathrm{Li}$ ($^{9}\mathrm{Li}+n+n$) is chosen as a challenging application for numerical calculations of practical interest. The detailed results are compared to existing experimental data, and good agreement is found at high excitation energies, where the isobaric analog and antianalog states are situated in the daughter nucleus. An interpretation of the decay pattern at lower excitation energies is suggested. Decays of the $^{9}\mathrm{Li}$ core and the two halo neutrons are individually treated and combined with the daughter system with almost unique isospin, which we predict to be broken by about $0.4%$ probability. Properties of decay products are predicted as possible future tests of this model.

Final-state interactions and spin structure in E1 breakup of Li11 in halo effective field theory

We calculate the $E1$ breakup of the $2n$ halo nucleus $^{11}\mathrm{Li}$ in halo effective field theory (Halo EFT) at leading order. In Halo EFT, $^{11}\mathrm{Li}$ is treated as a three-body system of a $^{9}\mathrm{Li}$ core and two neutrons. We present a detailed investigation of final-state interactions (FSIs) in the neutron-neutron $(nn)$ and neutron-core $(nc)$ channels. We employ M\o{}ller operators to formulate an expansion scheme that satisfies the non-energy-weighted cluster sum rule and successively includes higher-order terms in the multiple-scattering series for the FSI. Computing the $E1$ strength up to third order in this scheme, we observe apparent convergence and good agreement with experiment. The neutron-neutron FSI is by far the most important contribution and largely determines the maximum value of the $E1$ distribution. However, inclusion of $nc$ FSI does shift the peak position to slightly lower energies. Moreover, we investigate the sensitivity of the $E1$ response to the spin structure of the neutron-$^{9}\mathrm{Li}$ interaction. We contrast results for an interaction that is the same in the spin-1 and spin-2 channels with one that is only operative in the spin-2 channel, and find that good agreement with experimental data is only obtained if the interaction is present in both spin channels. The latter case is shown to be equivalent to a calculation in which the spin of $^{9}\mathrm{Li}$ is neglected.

Fusion reactions including weakly-bound and halo nuclei around Coulomb barrier

Fusion reactions including weakly-bound and halo nuclei around Coulomb barrier

Targeting a Nuclear Halo

Targeting a Nuclear Halo

Scattering of 15C on 208Pb at energies near the Coulomb barrier: Study of the experimental device response via the 12C+208Pb scattering

There are evidences that the 15C nucleus has an extended neutron distribution or a "neutron halo", but this situation is far from clear. If 15C has 1n-halo, the scattering dynamics should be affected and the angular distribution of the elastic channels should be sensitive to coupling effects due to the halo configuration. The objetive of this study is to understand the role of the halo in 15C by investigating its dynamical response in intense electric fields at energies close to the Coulomb barrier. For this purpose experiment IS619 was conducted performing the 15C + 208Pb elastic scattering reaction at HIE-ISOLDE, CERN. The beam energy was 4.37 MeV/u, which is very close to the Coulomb barrier of the system. The experimental setup used was the global detection system GLORIA, a six silicon telescopes array enable to measure the energy and angular distributions of the scattered particles. During the experiment, the 12C+208Pb scattering at 4.37 MeV/u was measured for calibration. The results of the 12C+208Pb measurement were used to fine-tune the geometry of the experimental setup and it is presented in this contribution.

Dineutron correlations in knockout reactions with Borromean halo nuclei

We study dineutron correlations in proton-target knockout reactions induced by Borromean two-neutron halo nuclei. Using a core + n + n three-body model for the projectile and a quasifree sudden reaction framework, we focus on the correlation angle as a function of the intrinsic neutron momentum. Our results indicate that the correlations are strong in a range of neutron momenta associated to the nuclear surface. We also discuss on the role of core excitations for such correlations.

Impact of core excitations in break-up reactions with halo nuclei

We revisit the resonant break-up of 19C on protons at intermediate energies. In this reaction, it was found, for the first time in a halo nucleus to our knowledge, that the cross section was largely dominated by the excitation of the core. In this contribution, we study the robustness of this conclusion against the choice of different optical potentials for the core.

Reaction studies with neutron-rich light nuclei at the upgraded SEC Device: Exploring the excited structure of 11Li

The 11Li nucleus is considered the best example of a two-neutron halo nucleus. While the structure of the ground state is well established there is still a significant debate regarding its excited states despite of the multiple experiments realised mainly from the excitation of the ground state of 11Li that is rather complex. We propose a novel approach, to directly feed the different excited states of 11Li by the (t,p) reaction as 9Li has a simpler structure. We will employ a 9Li beam produced at ISOLDE and post-accelerated by HIE-ISOLDE to energies of 7 MeV/u to impinge on a 3H-target located at the upgraded SEC station, this station contains a new particle detection set up: composed of 5 Si-particle telescopes in a pentagon configuration with end caps consisting of 2 CD Si detectors downstream and 1 CD upstream has been prepared to offer the maximum angular coverage and resolution. Geant4 Monte Carlo simulations with the efficiency of the setup is presented in the following proceeding.

Proton emission from halo nuclei induced by intense x-ray lasers

We investigate the proton emission from halo nuclei induced by intense x-ray lasers within the framework of a nonperturbative quantum $S$-matrix approach. We have analytically deduced the angular differential as well as the total multiphoton rates of the proton emissions. For a linearly polarized x-ray laser field, we find that the angular distributions of proton emission sensitively depend on the laser frequency and show an interesting petal structure with increasing laser frequency as well as the number of absorbed photons. Meanwhile, we find the Coulomb repulsion potential between the proton and the remainder nucleus has a strong hindering effect on the total multiphoton rates of the proton emissions and leads to the blueshifts of the multiphoton transition frequency. Moreover, the polarization effects of laser fields on total rates of proton emission have also been addressed. We find that the polarized ellipticity corresponding to the maximum of the total rates depends on the laser frequency showing a transition from perturbative to nonperturbative proton emission. The underlying mechanism of the above findings is uncovered, and some implications are discussed.

High-energy nucleus–nucleus collision and halo radii in different approaches of Glauber theory

The complete Glauber calculation of the differential cross-sections of [Formula: see text]–[Formula: see text] and halo nuclei on [Formula: see text] scattering was performed using the previously proposed in Y. M. Shabelski and A. G. Shuvaev [Phys. Rev. C 104, 064607 (2021); Mod. Phys. Lett. A 37, 2250081 (2022)] method of generating function. The results are different as compared with the similar calculations in the optical model and the rigid target approximation. The halo nuclei radii extracted from the scattering data via the complete Glauber analysis come out to be larger than those obtained in the approximate approaches.

Breakup of the proton halo nucleus 8B near barrier energies

The dynamics of a nuclear open quantum system could be revealed in the correlations between the breakup fragments of halo nuclei. The breakup mechanism of a proton halo nuclear system is of particular interest as the Coulomb polarization may play an important role, which, however, remains an open question. Here we use a highly efficient silicon detector array and measure the correlations between the breakup fragments of 8B incident on 120Sn at near-barrier energies. The energy and angular correlations can be explained by a fully quantum mechanical method based on the state-of-the-art continuum discretized coupled channel calculations. The results indicate that, compared to the neutron halo nucleus 6He, 8B presents distinctive reaction dynamics: the dominance of the elastic breakup. This breakup occurs mainly via the short-lived continuum states, almost exhausts the 7Be yield, indicating the effect of Coulomb polarization on the proton halo state. The correlation information reveals that the prompt breakup mechanism dominates, occurring predominantly on the outgoing trajectory. We also show that, as a large environment, the continuum of 8B breakup may not significantly influence elastic scattering and complete fusion.

Two particles interacting via a contact interaction on S^2

We consider two particles interacting via a contact interaction that are constrained to a sphere, or S^2. We determine their spectrum to arbitrary precision and for arbitrary angular momentum. We show how the non-inertial frame leads to non-trivial solutions for different angular momenta. Our results represent an extension of the finite-volume Lüscher formulas but now to a non-trivial geometry. We apply our results to predict the spectrum of select two-nucleon halo nuclei and compare with experimental results.

Effect of different nucleon–nucleon interactions based on relativistic mean field theory on elastic scattering cross-sections of proton and neutron halo nuclei

Effect of different nucleon–nucleon interactions based on relativistic mean field theory on elastic scattering cross-sections of proton and neutron halo nuclei

Momentum-space structure of dineutrons in Borromean nuclei

A comparative study is made of the momentum-space structure of dineutrons in the Borromean nuclei $^{11}\mathrm{Li}$, $^{6}\mathrm{He}$, $^{22}\mathrm{C}$, and $^{19}\mathrm{B}$. The ground-state properties of these nuclei are well described by a three-body model using a newly constructed finite-range $nn$ interaction in momentum space. I clarify how the mean opening angle between momenta of valence neutrons and the opening-angle distribution reflect the two-neutron density of the Borromean nuclei. By indicating the similarities to the distributions for the correlation angle in the knockout-reaction experiments, I show that the angular correlations of halo neutrons can provide rich information for the characteristic structure of dineutrons in the Borromean nuclei.

Study of Nuclear Contribution to Breakup Cross Section of 11Be Halo Nuclei within Time-Dependent Approach

Study of Nuclear Contribution to Breakup Cross Section of 11Be Halo Nuclei within Time-Dependent Approach

Study of bound and resonance states of 11Be in breakup reaction

We investigate the Coulomb breakup of the 11 Be halo nuclei on a lead target within non-perturbative time-dependent approach in a wide range of beam energy (5–70 MeV/nucleon) including the low-lying resonances in different partial and spin states of 11 Be. We have found considerable contribution of the low-lying resonances ( 5/2+ , 3/2− and 3/2+ ) to the breakup cross section of 11 Be. The obtained results are in good agreement with existing experimental data at 69 MeV/nucleon. The developed computational scheme opens new possibilities in investigation of Coulomb, as well as nuclear, breakup of other halo nuclei on heavy, as well as, light targets.

Coupled-channel description for mirror mass-11 nuclei compared to shell-model structures

The spectra of mass-11 nuclei are unusual, and so pose a challenge for nuclear-structure theory. Relating to nucleon emission, the set of isobars range from being well-bound (^{11}B,^{11}C) through weakly bound (^{11}Li, ^{11}Be), to being proton unstable (^{11}N,^{11}O). To add complexity, the weakly bound ^{11}Li takes the form of a two-nucleon halo nucleus. A self-consistent approach to understand this set of nuclei is especially important as the mirror pair ^{11}Be-^{11}N exhibit a parity-inverted ground state compared to their neighboring nuclei. Herein, the Multi-Channel Algebraic Scattering method (MCAS) has been used to describe the low excitation spectra of those isobars in terms of nucleon-nucleus clusters. A collective model description of the low-excitation states of the mass-10 mass-10 core nuclei has been used to form the coupled-channel interactions required in the method. For comparison, and to understand the underlying configurations, a shell model approach has been used to obtain those spectra with no-core (0+2+4)hbar omega and (0+2)hbar omega shell-model spaces for the mass 10 and mass 11 nuclei respectively. The results of the calculations suggest the need of a strong coupling in the collective coupled-channel vibrational model. In particular, the strong coupling of the collective 2^+_1 state of ^{10}Be to the valence neutron plays a decisive role in forming the positive parity ground state in ^{11}Be; an effect confirmed by the shell-model results.

Two-dimensional extrapolation procedure for an ab initio study of nuclear size parameters and the properties of the halo nucleus He6

A new two-dimensional procedure for extrapolation of the values of matter, neutron, and proton radii obtained in no-core shell model (NCSM) calculations to infinite size of its basis is proposed. A relationship between the radii is used as an additional test. Together with the JISP16 potential, which is frequently used in NCSM calculations of the radii, the Daejeon16 potential is applied for these purposes for the first time. Halo nucleus 6He is the object of studies. The small spread of radii values, successful testing using relationship between the values of these three radii, and reasonable agreement between the obtained results and experimental data as well as the results of other advanced ab initio calculations demonstrate the high efficiency of the developed approach and, therefore, good prospects for its application. The performed investigations and analysis of the results of other studies indicate that the halo of 6He has a large size 0.7 - 0.8 fm.

Study of resonances in exotic neutron-rich 14Be by the use of isospectral potential

In this work, Hyperspherical Harmonic Expansion (HHE) formalism aided by supersymmetric quantum mechanics is used to study bound and resonant states of 14Be in the three-body (12Be+ n + n) cluster model, and the analysis of the resonant states close to the binding threshold utilizes supersymmetric quantum mechanics (SSQM). GPT nucleon-nucleon potential together with SBB core-nucleon potential is chosen for the solution of three-body Schrödinger equation to get the lowest bound state energy and wave function. In the next stage, energy and wave function of the bound state is used to derive an isospectral potential that exhibit deep well following a strong barrier facilitating confinement (or trapping) of particle inside it at some positive energy (E>0). The trapping probability when plotted against energy shows a prominent peak at the energy of resonance. WKB approximation is used to determine the width of resonance width. Calculated resonance energy and width of resonance are compared with those measured experimentally for the promising neutron halo candidate, the 14Be.