Self-weakening of the tensor interaction in a nucleus

Zamick, Larry; Zheng, D. C.; Fayache, M. S.

doi:10.1103/physrevc.51.1253

Cited by 16 publications

(25 citation statements)

References 21 publications

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“…Thus, the A = 14 system affords us one of the few instances where one can study the elusive effects of the tensor interaction in nuclear structure [4,5]. Visscher and Ferrel [6] plotted the strength parameters of the spin-orbit and tensor interactions for which one could get the GT matrix element to vanish.…”

Section: Introductionmentioning

confidence: 99%

Allowed Gamow–Teller excitations from the ground state of 14N

et al. 2003

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Motivated by the proposed experiment 14 N (d, 2 He) 14 C, we study the final states which can be reached via the allowed Gamow-Teller mechanism. Much emphasis has been given in the past to the fact that the transition matrix element from the J π = 1 + T = 0 ground state of 14 N to the J π = 0 + T = 1 ground state of 14 C is very close to zero, despite the fact that all the quantum numbers are right for an allowed transition. We discuss this problem, but, in particular, focus on the excitations to final states with angular momenta 1 + and 2 + . We note that the summed strength to the J π = 2 + T = 1 states, 1 calculated with a wide variety of interactions, is significantly larger than that to the J π = 1 + T = 1 final states.

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Section: Introductionmentioning

confidence: 99%

Allowed Gamow–Teller excitations from the ground state of 14N

et al. 2003

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“…Just below a double shell closure, the valence nucleons of 14 C inhabit a region with a large nuclear density. But more important is the sensitivity of this GT matrix element to the nuclear tensor force, which as articulated by Zamick and collaborators [18,19] is one of the few instances in nuclear structure where the role of the tensor force is clearly revealed. In fact, with a residual interaction consisting of only central and spin-orbit forces it is not possible to achieve a vanishing matrix element in a pure p −2 configuration [20].…”

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confidence: 99%

Shell Model Description of theC14DatingβDecay with Brown-Rho-ScaledNNInteraction

et al. 2008

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We present shell model calculations for the β-decay of 14 C to the 14 N ground state, treating the states of the A = 14 multiplet as two 0p holes in an 16 O core. We employ low-momentum nucleon-nucleon (NN) interactions derived from the realistic Bonn-B potential and find that the Gamow-Teller (GT) matrix element is too large to describe the known lifetime. By using a modified version of this potential that incorporates the effects of Brown-Rho scaling medium modifications, we find that the GT matrix element vanishes for a nuclear density around 85% that of nuclear matter. We find that the splitting between the (J π , T ) = (1 + , 0) and (J π , T ) = (0 + , 1) states in 14 N is improved using the medium-modified Bonn-B potential and that the transition strengths from excited states of 14 C to the 14 N ground state are compatible with recent experiments.The beta decay of 14 C to the 14 N ground state has long been recognized as a unique problem in nuclear structure. Its connection to the radiocarbon dating method, which has had a significant impact across many areas of science, makes the decay of broad interest even beyond nuclear physics. But a priori one would not expect the beta decay of 14 C to be a good transition for radiocarbon dating over archaeological times, because the quantum numbers of the initial state (J π , T ) = (0 + , 1) and final state (J π , T ) = (1 + , 0) satisfy the selection rules for an allowed Gamow-Teller transition. The expected half-life would therefore be on the order of hours, far from the unusually long value of 5730 years [1] observed in nature. The corresponding nuclear transition matrix element is very small (≃ 2 × 10 −3 ) and is expected to result from an accidental cancellation among the different components contributing to the transition amplitude. This decay has therefore been used to investigate phenomena not normally considered in studies of allowed transitions, such as meson exchange currents [2,3], relativistic effects [4], and configuration mixing [5,6]. Of broader importance, however, is that this decay provides a very sensitive test for the in-medium nuclear interaction and in particular for the current efforts to extend the microscopic description of the nuclear force beyond that of a static two-body potential fit to the experimental data on two-nucleon systems. One such approach is to include hadronic medium modifications, in which the masses of mesons and nucleons are altered at finite density due to the partial restoration of chiral symmetry [7,8,9] or many-body interactions with either intermediate nucleon-antinucleon excitations [10] or resonance-hole excitations [11]. These effects are traditionally incorporated in models of the three-nucleon force (3NF), which have been well-tested in ab initio nuclear structure calculations of light nuclei [12,13].In this Letter we suggest that a large part of the observed 14 C beta decay suppression arises from inmedium modifications to the nuclear interaction. We study the problem from the perspective of Brown-Rho scaling (...

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“…Calculations of alpha-chain states in 12C and 160 have been made by Zamick and Zheng [45]. There are however three 2 § states around 17 MeV that decay into 8Be and at least one alpha-particle, and they may have a chain-structure.…”

Section: Alpha-chain Statesmentioning

confidence: 99%

A survey of alpha-clustering

Hodgson

1994

Z. Physik A - Hadrons and Nuclei

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The concept of alpha-clustering has found many applications to nuclear reactions and nuclear structure. Calculations of the properties of nuclear matter indicate that condensation into alpha-particles occurs when the density is somewhat less than the central nuclear density, suggesting that alpha clustering is favoured in the nuclear surface. This provides an explanation of alpha-decay which is now quantitatively successful. The concept of the alpha-particle mean field is now widely used to unify the alpha-particle bound and unbound states found by alpha-transfer reactions, and the scattering of alpha-particles by nuclei. The analysis of the structure of 44Ti using the alpha-4~ potential has been particularly successful. There are now several phenomenological alpha-alpha interactions that fit the low energy phase shifts, and these are used to calculate the structure of light nuclei, particularly those composed of 2N protons and 2N neutrons. Many excited states of such nuclei can be studied in this way, and a particularly interesting class of states is those composed of a linear chain of alpha-particles, some of which have been identified experimentally.

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Self-weakening of the tensor interaction in a nucleus

Cited by 16 publications

References 21 publications

Allowed Gamow–Teller excitations from the ground state of 14N

Allowed Gamow–Teller excitations from the ground state of 14N

Shell Model Description of theC14DatingβDecay with Brown-Rho-ScaledNNInteraction

A survey of alpha-clustering

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