| 1. |
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| 2. |
- Aksouh, F., et al.
(author)
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STUDY OF THE O-15(2p,gamma)Ne-17 CROSS SECTION BY COULOMB DISSOCIATION OF Ne-17 FOR THE rp PROCESS OF NUCLEOSYNTHESIS
- 2014
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In: Acta Physica Polonica, Series B.. - 1509-5770 .- 0587-4254. ; 45:2, s. 229-234
-
Journal article (peer-reviewed)abstract
- The O-15(2p, gamma)Ne-17 cross section has been studied by the inverse reaction, the Coulomb dissociation of Ne-17. The experiment has been performed at the GSI. The Ne-17 excitation energy prior to decay has been reconstructed by using the invariant-mass method. The preliminary differential and integral Coulomb dissociation cross sections (sigma(Coul)) have been extracted, which provide a photoabsorption (sigma(photo)) and a radiative capture cross section (sigma(cap)). Additionally, important information about the Ne-17 nuclear structure will be obtained. The analysis is in progress.
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| 3. |
- Burda, O., et al.
(author)
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Resonance parameters of the first 1/2+ state in 9Be and astrophysical implications
- 2010
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 82:1
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Journal article (peer-reviewed)abstract
- Spectra of the Be-9(e, e') reaction have been measured at the Superconducting Darmstadt Electron Linear Accelerator at an electron energy of E-0 = 73 MeV and scattering angles of 93 degrees and 141 degrees with high-energy resolution up to excitation energies of E-x = 8 MeV. The astrophysically relevant resonance parameters of the first excited 1/2(+) state of Be-9 have been extracted in a one-level approximation of R-matrix theory, resulting in resonance energy E-R = 1.748(6) MeV and width Gamma(R) = 274(8) keV, which are in good agreement with the latest Be-9(gamma, n) experiment but with considerably improved uncertainties. However, the reduced B(E1) transition strength deduced from an extrapolation of the (e, e') data to the photon point is smaller by a factor of two. Implications of the new results for possible production of C-12 in neutron-rich astrophysical scenarios are discussed.
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| 4. |
- Ekstrom, A., et al.
(author)
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Optimized Chiral Nucleon-Nucleon Interaction at Next-to-Next-to-Leading Order
- 2013
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 110:19, s. Art. no. 192502-
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Journal article (peer-reviewed)abstract
- We optimize the nucleon-nucleon interaction from chiral effective field theory at next-to-next-to-leading order (NNLO). The resulting new chiral force NNLOopt yields chi(2) approximate to 1 per degree of freedom for laboratory energies below approximately 125 MeV. In the A = 3, 4 nucleon systems, the contributions of three-nucleon forces are smaller than for previous parametrizations of chiral interactions. We use NNLOopt to study properties of key nuclei and neutron matter, and we demonstrate that many aspects of nuclear structure can be understood in terms of this nucleon-nucleon interaction, without explicitly invoking three-nucleon forces.
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| 5. |
- Forssen, Christian, 1974, et al.
(author)
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Living on the edge of stability, the limits of the nuclear landscape
- 2013
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In: Physica Scripta. - : IOP Publishing. - 1402-4896 .- 0031-8949. ; T152:T152, s. 014022-
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Journal article (peer-reviewed)abstract
- A first-principles description of nuclear systems along the drip lines presents a substantial theoretical and computational challenge. In this paper, we discuss the nuclear theory roadmap, some of the key theoretical approaches, and present selected results with a focus on long isotopic chains. An important conclusion, which consistently emerges from these theoretical analyses, is that three-nucleon forces are crucial for both global nuclear properties and detailed nuclear structure, and that many-body correlations due to the coupling to the particle continuum are essential as one approaches particle drip lines. In the quest for a comprehensive nuclear theory, high performance computing plays a key role.
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| 6. |
- Forssen, Christian, 1974, et al.
(author)
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Systematics of 2+ states in C isotopes from the no-core shell model
- 2013
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In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 40:5, s. 055105-
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Journal article (peer-reviewed)abstract
- We study low-lying states of even carbon isotopes in the range A = 10-20 within the large-scale no-core shell model. Using several accurate nucleon-nucleon (NN) as well as NN plus three-nucleon (NNN) interactions, we calculate excitation energies of the lowest 2(+) state, the electromagnetic B(E2; 2(1)(+) -> 0(1)(+)) transition rates, and the 2(1)(+) quadrupole moments as well as selected electromagnetic transitions among other states. Recent experimental campaigns to measure 2(+)-state lifetimes indicate an interesting evolution of nuclear structure that pose a challenge to reproduce theoretically from first principles. Our calculations do not include any effective charges or other fitting parameters. However, calculated results extrapolated to infinite model spaces are also presented. The model-dependence of those results is discussed. Overall, we find good agreement with the experimentally observed trends, although our extrapolated B(E2; 2(1)(+) -> 0(1)(+)) value for C-16 is lower compared to the most recent measurements. Relative transition strengths from higher excited states are investigated and the influence of NNN forces is discussed. In particular for 16C we find a remarkable sensitivity of the transition rates from higher excited states to the details of the nuclear interactions.
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| 7. |
- Forssen, Christian, 1974, et al.
(author)
-
The ab initio No-Core Shell Model and Light Nuclei
- 2011
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In: Few-Body Systems. - : Springer Science and Business Media LLC. - 1432-5411 .- 0177-7963. ; 49:1-4, s. 11-18
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Journal article (peer-reviewed)abstract
- The ab initio no-core shell model (NCSM) is a well-established theoretical framework aimed at an exact description of nuclear structure starting from high-precision interactions between the nucleons. In the NCSM we consider a system of A point-like, non-relativistic nucleons that interact by realistic inter-nucleon interactions. We consider two-nucleon interactions that reproduce nucleon-nucleon phase shifts with high precision, typically up to 350 MeV lab energy. We can also include three-nucleon interactions with terms, e.g., related to two-pion exchanges with an intermediate delta excitation. Both semi-phenomenological potentials, based on meson-exchange models, as well as modern chiral interactions can be considered. The performance of the NCSM within nuclear physics will be exemplified by showing results from studies of light nuclei. Major challenges in the future development of the method will be outlined.
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| 8. |
- Johansson, Håkan T, 1977, et al.
(author)
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The unbound isotopes He-9,He-10
- 2010
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In: Nuclear Physics A. - Elsevier : Elsevier BV. - 0375-9474 .- 1873-1554. ; 842:1-4, s. 15-32
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Journal article (peer-reviewed)abstract
- The unbound nuclei He-9 and He-10 have been produced in proton-knockout reactions from a 280 MeV/u Li-11 beam impinging on a liquid hydrogen target at the ALADIN-LAND setup at GSI. Information on their nuclear structure has been obtained from the relative-energy spectra, He-8 + n and He-8 + 2n, employing reaction models incorporating the structure of Li-11. The (8H)e + n relative-energy spectrum is dominated by a strong peak-like structure at low energy, which may be interpreted within the effective-range approximation as the result of an s-wave interaction with a neutron scattering length of -3.17(66) fm. This spectrum also shows evidence for resonance states at 1.33(8) MeV and at 2.4 MeV above the He-8 + n threshold. It is argued that the s-state might not be the He-9 ground state. For He-8 + n + n, the analysis of the relative-energy spectrum gives two alternative possibilities for an interpretation: either a narrow resonance at 1.42(10) MeV (Gamma = 1.11(76) MeV) superimposed on a correlated background, or two overlapping resonances, a ground state at 1.54(11) MeV (Gamma = 1.91(41) MeV) together with an excited state at 3.99(26) MeV (Gamma = 1.64(89) MeV). The two possible interpretations are discussed. (C) 2010 Elsevier B.V. All rights reserved.
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| 9. |
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| 10. |
- Kim, Youngman, et al.
(author)
-
Ab initio no core full configuration approach for light nuclei
- 2014
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In: Chiral Symmetry in Hadrons and Nuclei. - : WORLD SCIENTIFIC. - 9789814618229 ; , s. 78-85
-
Book chapter (other academic/artistic)abstract
- Comprehensive understanding of the structure and reactions of light nuclei poses theoretical and computational challenges. Still, a number of ab initio approaches have been developed to calculate the properties of atomic nuclei using fundamental interactions among nucleons. Among them, we work with the ab initio no core full configuration (NCFC) method and ab initio no core Gamow Shell Model (GSM). We first review these approaches and present some recent results.
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| 11. |
- Kim, Youngman, et al.
(author)
-
Ab initio no core full configuration approach for light nuclei
- 2014
-
In: International Journal of Modern Physics E. - 0218-3013. ; 23:7, s. Article no. 1461004 -
-
Journal article (peer-reviewed)abstract
- Comprehensive understanding of the structure and reactions of light nuclei poses theoretical and computational challenges. Still, a number of ab initio approaches have been developed to calculate the properties of atomic nuclei using fundamental interactions among nucleons. Among them, we work with the ab initio no core full configuration (NCFC) method and ab initio no core Gamow Shell Model (GSM). We first review these approaches and present some recent results.
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| 12. |
- Lindgren, E. J., et al.
(author)
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Fermionization of two-component few-fermion systems in a one-dimensional harmonic trap
- 2014
-
In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 16
-
Journal article (peer-reviewed)abstract
- The nature of strongly interacting Fermi gases and magnetism is one of the most important and studied topics in condensed-matter physics. Still, there are many open questions. A central issue is under what circumstances strong short-range repulsive interactions are enough to drive magnetic correlations. Recent progress in the field of cold atomic gases allows one to address this question in very clean systems where both particle numbers, interactions and dimensionality can be tuned. Here we study fermionic few-body systems in a one dimensional harmonic trap using a new rapidly converging effective-interaction technique, plus a novel analytical approach. This allows us to calculate the properties of a single spin-down atom interacting with a number of spin-up particles, a case of much recent experimental interest. Our findings indicate that, in the strongly interacting limit, spin-up and spin-down particles want to separate in the trap, which we interpret as a microscopic precursor of one-dimensional ferromagnetism in imbalanced systems. Our predictions are directly addressable in current experiments on ultracold atomic few-body systems.
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| 13. |
- Marganiec, C., et al.
(author)
-
Coulomb breakup of 17Ne from the viewpoint of nuclear astrophysics
- 2013
-
In: Proceedings of Science.
-
Conference paper (peer-reviewed)abstract
- By the Coulomb breakup of 17Ne, the time-reversed reaction 15O(2p,γ)17Ne has been studied. This reaction might play an important role in the rp process, as a break-out reaction of the hot CNO cycle. The secondary 17Ne ion beam with an energy of 500 MeV/nucleon has been dissociated in a Pb target. The reaction products have been detected with the LAND-R3B experimental setup at GSI. The preliminary differential and integral Coulomb dissociation cross section sCoul has been determined, which then will be converted into a photo-absorption cross section sphot o, and a two-proton radiative capture cross section σcap. Additionally, information about the structure of the 17Ne, a potential two-proton halo nucleus, will be received. The analysis is in progress.
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| 14. |
- Marganiec, J., et al.
(author)
-
Coulomb breakup of 17Ne from the viewpoint of nuclear astrophysics
- 2012
-
In: Proceedings of Science. - Proceedings of Science : Sissa. - 1824-8039.
-
Conference paper (peer-reviewed)abstract
- By the Coulomb breakup of 17Ne, the time-reversed reaction 15O(2p,γ)17Ne has been studied. This reaction might play an important role in the rp process, as a break-out reaction of the hot CNO cycle. The secondary 17Ne ion beam with an energy of 500 MeV/nucleon has been dissociated in a Pb target. The reaction products have been detected with the LAND-R3B experimental setup at GSI. The preliminary differential and integral Coulomb dissociation cross section sCoul has been determined, which then will be converted into a photo-absorption cross section sphoto, and a two-proton radiative capture cross section σcap. Additionally, information about the structure of the 17Ne, a potential two-proton halo nucleus, will be received. The analysis is in progress. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
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| 15. |
- Orce, J. N., et al.
(author)
-
Reorientation-effect measurement of the (2+ 1 Eˆ22+ 1) matrix element in 10Be
- 2012
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 86:4
-
Journal article (peer-reviewed)abstract
- The highly-efficient and segmented TIGRESS gamma-ray spectrometer at TRIUMF has been used to perform a reorientation-effect Coulomb-excitation study of the 2(1)(+) state at 3.368 MeV in Be-10. This is the first Coulomb-excitation measurement that enables one to obtain information on diagonal matrix elements for such a high-lying first excited state from gamma-ray data. With the availability of accurate lifetime data, a value of -0.110 +/- 0.087 eb is determined for the diagonal matrix element, which assuming the rotor model, leads to a negative spectroscopic quadrupole moment of Q(S)(2(1)(+)) = -0.083 +/- 0.066 eb. This result is in agreement with both no-core shell-model calculations performed in this work with the CD-Bonn 2000 two-nucleon potential and large shell-model spaces, and Green's function Monte Carlo predictions with two-plus three-nucleon potentials.
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| 16. |
- Petri, M., et al.
(author)
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Structure of C-16: Testing shell model and ab initio approaches
- 2012
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 86:4, s. Art. no. 044329-
-
Journal article (peer-reviewed)abstract
- Excited states in C-16 were populated via the Be-9(N-17,C-16+gamma)X one-proton knockout reaction. The lifetime of the 2(1)(+) state in C-16 was measured using the recoil distance method. The extracted lifetime of tau(+)(21) = 11.4(-0.9)(+0.8)(stat) +/- 0.7(syst(B rho))(-1.5)(+0.0)(syst(feeding)) ps yields a deduced B(E2;2(1)(+) -> 0(1)(+)) = 4.21(-0.26)(+0.34)(stat)(-0.24)(+0.28)(syst(B rho))(-0.00)(+0.64)(syst(feeding)) e(2)fm(4) value in good agreement with a previous measurement. The one-proton knockout cross section is used to extract the proton amplitude of the C-16 2(1)(+) state, which confirms the neutron dominant character of this state. Gamma-ray branching ratios between the 2(2)(+) state and the 2(1)(+) and ground states were also determined. The results are compared with p-sd shell model and no-core shell model (with NN and NN + NNN) calculations. The inclusion of three-body forces are essential in order for the no-core shell model calculations to reproduce the experimental findings on the gamma-ray branching ratios.
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| 17. |
- RYBERG, EMIL, 1987, et al.
(author)
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Constraining low-energy proton capture on beryllium-7 through charge radius measurements
- 2014
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In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 50:11, s. 170-182
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Journal article (peer-reviewed)abstract
- In this paper, we point out that a measurement of the charge radius of boron-8 provides indirect access to the S-factor for radiative proton capture on beryllium-7 at low energies. We use leading-order halo effective field theory to explore this correlation and we give a relation between the charge radius and the S-factor. Furthermore, we present important technical aspects relevant to the renormalization of point-like P -wave interactions in the presence of a repulsive Coulomb interaction.
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| 18. |
- RYBERG, EMIL, 1987, et al.
(author)
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Effective field theory for proton halo nuclei
- 2014
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 89:1
-
Journal article (peer-reviewed)abstract
- We use halo effective field theory to analyze the universal features of proton halo nuclei bound due to a large S-wave scattering length. Our work provides a fully field-theoretical treatment of bound halo nuclei in the presence of a repulsive Coulomb interaction. With a Lagrangian built from effective core and valence-proton fields, we derive a leading-order expression for the charge form factor. Within the same framework we also calculate the radiative proton capture cross section. We present general results at leading order that can be applied to any one-proton halo system bound in a relative S wave. We illustrate the method by studying the excited 1/2(+) state of fluorine 17, for which we give results for the charge radius and the astrophysical S factor.
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| 19. |
- SÄÄF, DANIEL, 1986, et al.
(author)
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Microscopic description of translationally invariant core+N+N overlap functions
- 2014
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 89:1, s. 011303-
-
Journal article (peer-reviewed)abstract
- We derive expressions for core+N+N overlap integrals starting from microscopic wave functions obtained in the ab initio no-core shell model. These overlap integrals correspond to three-body channel form factors and can be used to investigate the clustering of many-body systems into a core plus two nucleons. We consider the case when the composite system and the core are described in Slater determinant, harmonic oscillator bases, and we show how to remove spurious center-of-mass components exactly in order to derive translationally invariant overlap integrals. We study in particular the Borromean 6He nucleus using realistic chiral nuclear interactions, and we demonstrate that the observed clusterization in this system is a Pauli focusing effect. The inclusion of three-body forces has a small effect on this structure. In addition, we discuss the issue of absolute normalization for spectroscopic factors, which we show is larger than one. As part of this study we also perform extrapolations of ground-state observables and investigate the dependence of these results on the resolution scale of the interaction.
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| 20. |
- Voss, P., et al.
(author)
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Excited-state transition-rate measurements in C-18
- 2012
-
In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 86:1
-
Journal article (peer-reviewed)abstract
- Excited states in C-18 were populated by the one-proton knockout reaction of an intermediate energy radioactive N-19 beam. The lifetime of the first 2(+) state was measured with the Koln/NSCL plunger via the recoil distance method to be tau (2(1)(+)) = 22.4 +/- 0.9(stat)(-2.2)(+3.3)(syst) ps, which corresponds to a reduced quadrupole transition strength of B(E2; 2(1)(+) -> 0(1)(+)) = 3.64(-0.14)(+ 0.15)(stat)(-0.47)(+0.40)(syst) e(2)fm(4). In addition, an upper limit on the lifetime of a higher-lying state feeding the 2(1)(+) state was measured to be tau
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| 21. |
- Wamers, F., et al.
(author)
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Exclusive measurements of nuclear breakup reactions of 17Ne
- 2014
-
In: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 66
-
Conference paper (peer-reviewed)abstract
- We have studied one-proton-removal reactions of about 500MeV/u 17Ne beams on a carbon target at the R3B/LAND setup at GSI by detecting beam-like 15O-p and determining their relative-energy distribution. We exclusively selected the removal of a 17Ne halo proton, and the Glauber-model analysis of the 16F momentum distribution resulted in an s2 contribution in the 17Ne ground state of about 40%. © Owned by the authors, published by EDP Sciences, 2014.
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| 22. |
- Åkerlund, O., et al.
(author)
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The similarity renormalization group for three-body interactions in one dimension
- 2011
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In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 47:10
-
Journal article (peer-reviewed)abstract
- We report on recent progress of the implementation of the similarity renormalization group (SRG) for three-body interactions in a one-dimensional, bosonic model system using the plane-wave basis. We discuss our implementation of the flow equations and show results that confirm that results in the three-body sector remain unchanged by the transformation of the Hamiltonian. We also show how the SRG transformation decouples low- from high-momentum nodes in the three-body sector and therefore simplifies the numerical calculation of observables.
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