Nuclear structure features of Gamow-Teller excitations

Zelevinsky, Vladimir; Auerbach, N.; Loc, Bui Minh

doi:10.1103/physrevc.96.044319

Cited by 12 publications

(10 citation statements)

References 18 publications

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“…In the 2p1f shell the estimated quenching factor is q=0.744, slightly smaller but statistically compatible with the 2s1dshell value [162]. An anticorrelation between the total Gamow-Teller strength and the transition rate of the collective quadrupole excitation has been observed [163,164], which can be simulated with artificial changes of the spin-orbit splitting [165].…”

Section: Shell Model Description Of Gamow-teller Strengths In 2p1f -Ssupporting

confidence: 62%

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Influence of pairing and deformation on charge exchange transitions

P̧ittel

Hirsch

2020

Rev. Mex. Fís.

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We describe the importance of charge-exchange reactions, and in particular Gamow-Teller transitions, first to astrophysical processes and double beta decay, and then to the understanding of nuclear structure. In our review of their role in nuclear structure we first provide an overview of some of the key steps in the emergence of our current understanding of the structure of nuclei, including the central role played by the isovector pairing and the quadrupole-quadrupole channels in the description of energy spectra and in the manifestation of collective modes, some associated with deformation of the nuclear shape. We then turned our focus to Gamow-Teller (GT) tran- sitions in relatively light nuclei, especially in the 2p1f shell, where isoscalar pairing may be playing a role in competition with the isovector pairing that dominates in heavier regions. Following a summary of the progress made in recent years on this subject, we report a systematic shell model study aimed at providing further clarification as to how these pairing modes compete. In this study, we use a schematic Hamiltonian that contains a quadrupole- quadrupole interaction as well as both isoscalar and isovector pairing interac- tions. We first find an optimal set of Hamiltonian parameters for the model, to provide a starting point from which to vary the relevant pairing strengths and thus assess how this impacts the behavior of GT transitions and the corresponding energy spectra and rotational properties of the various nuclei involved in the decays. The analysis includes as an important theme a com- parison with experimental data. The need to suppress the isoscalar pairing mode when treating nuclei with a neutron excess to avoid producing spurious results for the ground state spin and parity with the simplified Hamiltonian is highlighted. Varying the strength parameters for the two pairing modes is found to exhibit different but systematic effects on GT transition properties and on the corresponding energy spectra, which are detailed.

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Section: Shell Model Description Of Gamow-teller Strengths In 2p1f -Ssupporting

confidence: 62%

“…An anticorrelation between between the total Gamow-Teller strength and the transition rate of the collective quadrupole excitation has been observed [163,164], which can be simulated with artificial changes of the spin-orbit splitting [165].…”

Section: Shell Model Description Of Gamow-teller Strengths In 2p1f -S...mentioning

confidence: 99%

Influence of pairing and deformation on charge exchange transitions

P̧ittel

Hirsch

2020

Rev. Mex. Fís.

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“…Again for the sd-shell, 32 S HF and PHF values are outliers, overestimating the M1 strength. Here the defect is not deformation but spin (although these are related [41,42]): the expectation value of total S 2 is larger when filling the 0d 5/2 and leaving the 0d 3/2 empty, than for the FCI solution, which partially restores spin symmetry. Additionally, in the pf shell three NPA cases, 59,60,61 Fe, provide notable overestimates of the M1 NEWSR.…”

Section: Resultsmentioning

confidence: 99%

Exact sum rules with approximate ground states

Johnson,

Luu,

2020

Preprint

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Electromagnetic and weak transitions tell us a great deal about the structure of atomic nuclei. Yet modeling transitions can be difficult: it is often easier to compute the ground state, if only as an approximation, than excited states. One alternative is through transition sum rules, in particular the non-energy-weighted and energy-weighted sum rules, which can be computed as expectation values of operators. We investigate by computing sum rules for a variety of nuclei, comparing the numerically exact full configuration-interaction shell model, as a reference, to Hartree-Fock, projected Hartree-Fock, and the nucleon pair approximation. These approximations yield reasonable agreement, which we explain by prior work on the systematics of transition moments.

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“…As it has been emphasized in Ref. [9], recent interest in the GTR studies is motivated by its importance for understanding the spin and spin-isospin dependence of modern effective interactions [10][11][12][13][14][15][16][17], nuclear beta decay [18][19][20][21][22][23][24][25][26], beta delayed neutron emission [27], as well as double beta decay [28][29][30][31][32][33][34][35][36]. In addition, accurate description of GT ± transitions, including both in stable and exotic nuclei, is relevant for the description of a variety of astrophysically relevant weak interaction processes [37][38][39][40][41], electron capture in presupernova stars [42][43][44], r-process [45,46] and neutrino-nucleus interaction of relevance for neutrino detectors and neutrino nucleosynthesis in stellar environment [47][48][49][50][51][52]…”

Section: Introductionmentioning

confidence: 99%

Nuclear charge-exchange excitations based on relativistic density-dependent point-coupling model

Vale,

Niu,

Paar

2020

Preprint

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Spin-isospin transitions in nuclei away from the valley of stability are essential for the description of astrophysically relevant weak interaction processes. While they remain mainly beyond the reach of experiment, theoretical modeling provides important insight into their properties. In order to describe the spin-isospin response, the proton-neutron relativistic quasiparticle random phase approximation (PN-RQRPA) is formulated using the relativistic density-dependent point coupling interaction, and separable pairing interaction in both the T = 1 and T = 0 pairing channels. By implementing recently established DD-PCX interaction with improved isovector properties relevant for the description of nuclei with neutron-to-proton number asymmetry, the isobaric analog resonances (IAR) and Gamow-Teller resonances (GTR) have been investigated.In contrast to other models that usually underestimate the IAR excitation energies in Sn isotope chain, the present model accurately reproduces the experimental data, while the GTR properties depend on the isoscalar pairing interaction strength. This framework provides not only an improved description of the spin-isospin response in nuclei, but it also allows future large scale calculations of charge-exchange excitations and weak interaction processes in stellar environment.

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Nuclear structure features of Gamow-Teller excitations

Cited by 12 publications

References 18 publications

Influence of pairing and deformation on charge exchange transitions

Influence of pairing and deformation on charge exchange transitions

Exact sum rules with approximate ground states

Nuclear charge-exchange excitations based on relativistic density-dependent point-coupling model

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