Isospin nonconserving interaction in the T = 1 analogue states of the mass-70 region

Self Cite

Simultaneous investigation of the T = 1 (J π = 0 + ) and T = 0 (J π = 9 + ) β decays in The β decay of the odd-odd nucleus 70 Br has been investigated with the BigRIPS and EURICA setups at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center. The T = 0 (J π = 9 + ) and T = 1 (J π = 0 + ) isomers have both been produced in in-flight fragmentation of 78 Kr with ratios of 41.6(8)% and 58.4(8)%, respectively. A half-life of t 1/2 = 2157 +53 −49 ms has been measured for the J π = 9 + isomer from γ-ray time decay analysis. Based on this result, we provide a new value of the half-life for the J π = 0 + ground state of 70 Br, t 1/2 = 78.42 ± 0.51 ms, which is slightly more precise, and in excellent agreement, with the best measurement reported hitherto in the literature. For this decay, we provide the first estimate of the total branching fraction decaying through the 2 + 1 state in the daughter nucleus 70 Se, R(2 + 1 ) = 1.3 ± 1.1%. We also report four new low-intensity γ-ray transitions at 661, 1103, 1561, and 1749 keV following the β decay of the J π = 9 + isomer. Based on their coincidence relationships, we tentatively propose two new excited states at 3945 and 4752 keV in 70 Se with most probable spins and parities of J π = (6 + ) and (8 + ), respectively. The observed structure is interpreted with the help of shell-model calculations, which predict a complex interplay between oblate and prolate configurations at low excitation energies.

Section: B Comparison With Shell-model Calculationssupporting

confidence: 73%

Section: B Comparison With Shell-model Calculationsmentioning

confidence: 99%

Simultaneous investigation of the T=1(Jπ=0+) and T=0(J

Morales¹,

Algora²,

Rubio³

et al. 2017

Self Cite

“…[26]. It has been shown [5] that the multipole, monopole, and spin-orbit forces are not sufficient to explain the experimental TED for A = 66 and that the INC force is important for reproducing the observed experimental data [2]. The INC force used in the present calculation comprises an isotensor strength of 100 keV for J = 0 couplings for all the orbitals included in the model space, which is consistent with that required to reproduce the empirical TED of the A = 42 triplet in the f 7/2 shell [27].…”

mentioning

confidence: 99%

“…It is of high interest to extend such studies to higher masses, where the structure of the low-spin states involved is very different, evolving from dominance by fp orbitals to g 9/2 orbitals by A = 74 [4]. Moreover, predictions for the TEDs already exist with and without the INC component [5]. Irrespective of the techniques employed, however, the study of exotic proton-rich nuclei is challenging due to their low production cross sections.…”

mentioning

confidence: 99%

Spectroscopy on the proton drip-line: Probing the structure dependence of isospin nonconserving interactions

Henderson¹,

Jenkins²,

Kaneko³

et al. 2014

Self Cite

The recoil-β tagging technique was used to identify transitions associated with the decay of the 2 + and, tentatively, the 4 + excited states in 74 Sr. Combining these results with published data for the A = 74 isobars, triplet energy differences (TEDs) have been extracted, the heaviest case for which these values have been evaluated. State-of-the-art shell-model calculations using the JUN45 interaction and incorporating a J = 0 isospin nonconserving (INC) interaction with an isotensor strength of 100 keV can reproduce the trend in the TED data, with particularly good agreement for the 2 + state. This agreement for the TED data taken together with the fact that agreement has also been shown between shell-model calculations with the same strength of INC interaction in the f 7/2 shell and recently for A = 66 strongly suggests that such an interaction exists throughout the nuclear chart and cannot have a strong dependence on details of nuclear structure such as which nuclear orbitals are occupied. It also supports the hypothesis that only a J = 0 component of the INC interaction need be included to explain the observed TEDs. Isospin symmetry is a central concept in nuclear physics, based on the idea that the proton and neutron are two isospin states of a single object, the nucleon. This would imply an identical pattern of excited states across a T = 1 isospin triplet. These symmetries are broken due to a number of nuclear structure effects, most importantly the fact that the proton carries an electric charge while the neutron does not. When exploring such breakdown of symmetries, it is instructive for the study of isospin triplets, to evaluate triplet energy differences (TEDs) as a function of spin J defined bySuch isotensor energy differences are essentially independent of single-particle effects, which makes them particularly simple. Since contributions involving Coulomb effects are readily calculable, TEDs are particularly sensitive to additional terms such as isospin nonconserving (INC) components. It has been shown that such a component is necessary to reproduce experimental mirror-energy differences (MEDs) in the f 7/2 shell [1]. Indeed, recent work identifying the (4 + 1 ) and (6 + 1 ) excited states in the N = Z − 2 nucleus 66 Se [2] has allowed the evaluation of the TEDs for A = 66, the first case above the 56 Ni closed shell; and it appears that an INC term is also mandatory in reproducing the TED. Nucleon-nucleon scattering data have previously been used to infer the INC component to the nuclear interaction, the isotensor component of which is consistent with that previously observed in the f 7/2 orbital [3]. The measurement of such a component in-medium is of considerable interest, and it is not yet clear whether the INC component arising from energy-difference measurements is indeed the same as that determined from scattering data. It is of high interest to extend such studies to higher masses, where the structure of the low-spin states involved is very different, evolving from dominance by fp orbitals...

“…However, the nucleon-nucleon scattering data suggested that v nn is slightly more attractive than v pp , and v np is stronger than (v nn + v pp )/2 [4,5]. In real nuclear systems where manybody effects are important [6], isospin symmetry breaking has long been an active research theme connected to different subfields, for examples, in understanding the precise values of the Cabbibo-Kobayashi-Maskawa (CKM) mixing matrix elements between the u and d quarks [7,8], the changes in nuclear structure near the N = Z line due to charge-violating nuclear force [9][10][11][12], and the influence in nova nucleosynthesis [13]. …”

mentioning

confidence: 99%

Generalized isobaric multiplet mass equation and its application to the Nolen-Schiffer anomaly

Zhang

Zuo

et al. 2018

Self Cite

The Wigner Isobaric Multiplet Mass Equation (IMME) is the most fundamental prediction in nuclear physics with the concept of isospin. However, it was deduced based on the Wigner-Eckart theorem with the assumption that all charge-violating interactions can be written as tensors of rank two. In the present work, the chargesymmetry breaking (CSB) and charge-independent breaking (CIB) components of the nucleon-nucleon force, which contribute to the effective interaction in nuclear medium, are established in the framework of Brueckner theory with AV18 and AV14 bare interactions. Because such charge-violating components can no longer be expressed as an irreducible tensor due to density dependence, its matrix element cannot be analytically reduced by the Wigner-Eckart theorem. With an alternative approach, we derive a generalized IMME (GIMME) that modifies the coefficients of the original IMME. As the first application of GIMME, we study the long-standing question for the origin of the Nolen-Schiffer anomaly found in the Coulomb displacement energy of mirror nuclei. We find that the naturally-emerged CSB term in GIMME is largely responsible for explaining the Nolen-Schiffer anomaly. Introduction. The similarity of proton and neutron masses and approximate symmetry of nucleon-nucleon interactions under the exchange of the two kinds of nucleons lead to the concept of isospin [1,2]. At the isospin-symmetry limit, the charge-symmetry requires that the free proton-proton interaction v pp excluding the Coulomb force is equal to the neutronneutron v nn , while the charge-independence requires that the neutron-proton interaction v np = (v nn + v pp )/2 [3]. However, the nucleon-nucleon scattering data suggested that v nn is slightly more attractive than v pp , and v np is stronger than (v nn + v pp )/2 [4,5]. In real nuclear systems where manybody effects are important [6], isospin symmetry breaking has long been an active research theme connected to different subfields, for examples, in understanding the precise values of the Cabbibo-Kobayashi-Maskawa (CKM) mixing matrix elements between the u and d quarks [7,8], the changes in nuclear structure near the N = Z line due to charge-violating nuclear force [9][10][11][12], and the influence in nova nucleosynthesis [13].