| 1. |
- Henderson, J., et al.
(author)
-
Coulomb excitation of the vertical bar T-z vertical bar=1/2, A=23 mirror pair
- 2022
-
In: PHYSICAL REVIEW C. - 2469-9985 .- 2469-9993. ; 105:3
-
Journal article (peer-reviewed)abstract
- Background: Electric-quadrupole (E2) strengths relate to the underlying quadrupole deformation of a nucleus and present a challenge for many nuclear theories. Mirror nuclei in the vicinity of the line of N = Z represent a convenient laboratory for testing deficiencies in such models, making use of the isospin symmetry of the systems. Purpose: Uncertainties associated with literature E2 strengths in Mg-23 are some of the largest in T-z = vertical bar 1/2 vertical bar nuclei in the sd shell. The purpose of the present paper is to improve the precision with which these values are known, to enable better comparison with theoretical models. Methods: Coulomb-excitation measurements of Mg-23 and Na-23 were performed at the TRIUMF-ISAC facility using the TIGRESS spectrometer. They were used to determine the E2 matrix elements of mixed E2/M1 transitions. Results: Reduced E2 transition strengths, B(E2), were extracted for Mg-23 and Na-23. Their precision was improved by factors of approximately 6 for both isotopes, while agreeing within uncertainties with previous measurements. Conclusions: A comparison was made with both shell-model and ab initio valence-space in-medium similarity renormalization group calculations. Valence-space in-medium similarity renormalization group calculations were found to underpredict the absolute E2 strength, in agreement with previous studies.
|
|
| 2. |
- Holl, Matthias, 1986, et al.
(author)
-
Beamline Simulation for the NNBAR Experiment at the European Spallation Source
- 2022
-
In: Proceedings of the 14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection and Shielding Division, ICRS 2022/RPSD 2022. - 9780894487866 ; , s. 431-434
-
Conference paper (peer-reviewed)abstract
- We have developed a sampling method for beamline simulations for the proposed NNBAR experiment at the European Spallation Source. The method is based on probability density evaluation and duct source biasing and enables the simulations of the entire NNBAR beamline with high statistics while also preserving correlations of the neutron tracks. Future efforts will focus on employing these methods for the investigation of the required thickness of the shielding for the NNBAR experiment and the estimation of the background that will reach the annihilation detector at the end of the beamline.
|
|
| 3. |
- Holl, Matthias, 1986, et al.
(author)
-
Border of the island of inversion: Unbound states in Ne-29
- 2022
-
In: Physical Review C. - 2469-9985 .- 2469-9993. ; 105:3
-
Journal article (peer-reviewed)abstract
- The nucleus Ne-29 is situated at the border of the island of inversion. Despite significant efforts, no bound low-lying intruder f(7/2) state, which would place Ne-29 firmly inside the island of inversion, has yet been observed. Here, the first investigation of unbound states of Ne-29 is reported. The states were populated in Ne-30(p, pn) and Na-30(p, 2p) reactions at a beam energy of around 230 MeV/nucleon, and analyzed in terms of their resonance properties, partial cross sections, and momentum distributions. The momentum distributions are compared to calculations using the eikonal, direct reaction model, allowing assignments for the observed states. The lowest lying resonance at an excitation energy of 1.48(4) MeV shows clear signs of a significant l = 3 component, giving first evidence for f(7/2) single particle strength in Ne-29. The excitation energies and strengths of the observed states are compared to shell-model calculations using the SDPF-U-MIX interaction.
|
|
| 4. |
- Lehr, C., et al.
(author)
-
Unveiling the two-proton halo character of 17 Ne: Exclusive measurement of quasi-free proton-knockout reactions
- 2022
-
In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 827
-
Journal article (peer-reviewed)abstract
- The proton drip-line nucleus 17Ne is investigated experimentally in order to determine its two-proton halo character. A fully exclusive measurement of the 17Ne(p,2p)16F→15⁎O+p quasi-free one-proton knockout reaction has been performed at GSI at around 500 MeV/nucleon beam energy. All particles resulting from the scattering process have been detected. The relevant reconstructed quantities are the angles of the two protons scattered in quasi-elastic kinematics, the decay of 16F into 15O (including γ decays from excited states) and a proton, as well as the 15O+p relative-energy spectrum and the 16F momentum distributions. The latter two quantities allow an independent and consistent determination of the fractions of l=0 and l=2 motion of the valence protons in 17Ne. With a resulting relatively small l=0 component of only around 35(3)%, it is concluded that 17Ne exhibits a rather modest halo character only. The quantitative agreement of the two values deduced from the energy spectrum and the momentum distributions supports the theoretical treatment of the calculation of momentum distributions after quasi-free knockout reactions at high energies by taking into account distortions based on the Glauber theory. Moreover, the experimental data allow the separation of valence-proton knockout and knockout from the 15O core. The latter process contributes with 11.8(3.1) mb around 40% to the total proton-knockout cross section of 30.3(2.3) mb, which explains previously reported contradicting conclusions derived from inclusive cross sections.
|
|
