221 research outputs found
Feasibility of extracting a admixture probability in the neutron-rich Li hypernucleus
We examine theoretically production of the neutron-rich Li
hypernucleus by a double-charge exchange (, ) reaction on a
B target with distorted-wave impulse approximation calculations. The
result shows that the magnitude and shape of the calculated spectrum at 1.20
GeV/c by a one-step mechanism via doorways
caused by a coupling can explain the
recent experimental data, and the admixture probability in
Li is found to be the order of 10 %. The (,
) reaction provides a capability of extracting properties of wave
functions with - coupling effects in neutron-rich nuclei,
together with the reaction mechanism.Comment: 13 pages, 3 figure
Tensor-optimized shell model for the Li isotopes with a bare nucleon-nucleon interaction
We study the Li isotopes systematically in terms of the tensor-optimized
shell model (TOSM) by using a bare nucleon-nucleon interaction as the AV8'
interaction. The short-range correlation is treated in the unitary correlation
operator method (UCOM). Using the TOSM+UCOM approach, we investigate the role
of the tensor force on each spectrum of the Li isotopes. It is found that the
tensor force produces quite a characteristic effect on various states in each
spectrum and those spectra are affected considerably by the tensor force. The
energy difference between the spin-orbit partner, the p1/2 and p3/2 orbits of
the last neutron, in 5Li is caused by opposite roles of the tensor correlation.
In 6Li, the spin-triplet state in the LS coupling configuration is favored
energetically by the tensor force in comparison with jj coupling shell model
states. In 7,8,9Li, the low-lying states containing extra neutrons in the p3/2
orbit are favored energetically due to the large tensor contribution to allow
the excitation from the 0s orbit to the p1/2 orbit by the tensor force. Those
three nuclei show the jj coupling character in their ground states which is
different from 6Li.Comment: 12 pages, 6 figures. arXiv admin note: text overlap with
arXiv:1108.393
Shell evolution and nuclear forces
We present a quantitative study of the role played by different components
characterizing the nucleon-nucleon interaction in the evolution of the nuclear
shell structure. It is based on the spin-tensor decomposition of an effective
two-body shell-model interaction and the subsequent study of effective
single-particle energy variations in a series of isotopes or isotones. The
technique allows to separate unambiguously contributions of the central, vector
and tensor components of the realistic effective interaction. We show that
while the global variation of the single-particle energies is due to the
central component of the effective interaction, the characteristic behavior of
spin-orbit partners, noticed recently, is mainly due to its tensor part. Based
on the analysis of a well-fitted realistic interaction in sdpf-shell model
space, we analyze in detail the role played by the different terms in the
formation and/or disappearance of N=16, N=20 and N=28 shell gaps in
neutron-rich nuclei.Comment: 6 pages, 4 figure
The - coupling effect in the neutron-rich -hypernucleus Li by microscopic shell model
We investigate the structure of the neutron-rich -hypernucleus
Li by using microscopic shell-model calculations considering a
- coupling effect. The calculated -mixing probability
in the Li ground state is found to be about 0.34 % which is
coherently enhanced by the - coupling configurations, leading
to the energy shift 0.28 MeV which is about 3 times larger than that in
Li. The importance of the configuration obtained by
the interaction and the potentiality of the neutron-rich environment
are discussed.Comment: 6 figure
Role of the tensor interaction in He isotopes with a tensor-optimized shell model
We studied the role of the tensor interaction in He isotopes systematically
on the basis of the tensor-optimized shell model (TOSM). We use a bare
nucleon-nucleon interaction AV8 obtained from nucleon-nucleon scattering data.
The short-range correlation is treated in the unitary correlation operator
method (UCOM). Using the TOSM+UCOM approach, we investigate the role of tensor
interaction on each spectrum in He isotopes. It is found that the tensor
interaction enhances the LS splitting energy observed in 5He, in which the p1/2
and p3/2 orbits play different roles on the tensor correlation. In {6,7,8}He,
the low-lying states containing extra neutrons in the p3/2 orbit gain the
tensor contribution. On the other hand, the excited states containing extra
neutrons in the p1/2 orbit lose the tensor contribution due to the
Pauli-blocking effect with the 2p2h states in the 4He core configuration.Comment: 11 pages, 8 figure
Shell-model calculations for p-shell hypernuclei
The interpretation of hypernuclear gamma-ray data for p-shell hypernuclei in
terms of shell-model calculations that include the coupling of Lambda- and
Sigma-hypernuclear states is briefly reviewed. Next, Lambda 8Li, Lambda 8Be,
and Lambda 9Li are considered, both to exhibit features of Lambda-Sigma
coupling and as possible source of observed, but unassigned, hypernuclear gamma
rays. Then, the feasibility of measuring the ground-state doublet spacing of
Lambda 10Be, which, like Lambda 9Li, could be studied via the (K-,pi0 gamma)
reaction, is investigated. Structural information relevant to the population of
states in these hypernuclei in recent (e,e'K+) studies is also given. Finally,
the extension of the shell-model calculations to sd-shell hypernuclei is
briefly considered.Comment: 17 pages, 3 figures. Contribution to special volume on Strangeness
Nuclear Physic
Production of doubly strange hypernuclei via {\Xi}- doorways in the 16O(K-, K+) reaction at 1.8 GeV/c
We examine theoretically production of doubly strange hypernuclei, 16 {\Xi}-C
and 16 {\Lambda}{\Lambda}C, in doublecharge exchange 16O(K-, K+) reactions
using a distorted-wave impulse approximation. The inclusive K+ spectrum at the
incident momentum pK- = 1.8 GeV/c and scattering angle {\theta}lab = 0^{\circ}
is estimated in a one-step mechanism, K-p \to K+{\Xi}- via {\Xi}- doorways
caused by a {\Xi}-p-{\Lambda}{\Lambda} coupling. The calculated spectrum in the
{\Xi}- bound region indicates that the integrated cross sections are on the
order of 7-12 nb/sr for significant 1- excited states with 14C(0+, 2+) \otimes
s{\Lambda}p{\Lambda} configurations in 16 {\Lambda}{\Lambda}C via the doorway
states of the spin-stretched 15N(1/2-, 3/2-) \otimes s{\Xi}- in 16 {\Xi}-C due
to a high momentum transfer q{\Xi}- \approx 400 MeV/c. The {\Xi}- admixture
probabilities of these states are on the order of 5-9%. However, populations of
the 0+ ground state with 14C(0+) \otimes s2{\Lambda} and the 2+ excited state
with 14C(2+) \otimes s2 {\Lambda} are very small. The sensitivity of the
spectrum on the {\Xi}N-{\Lambda}{\Lambda} coupling strength enables us to
extract the nature of {\Xi}N-{\Lambda}{\Lambda} dynamics in nuclei, and the
nuclear (K-, K+) reaction can extend our knowledge of the S = -2 world.Comment: 10 pages, 3 figure
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