γ transitions inA=7hypernuclei and a possible derivation of hypernuclear size

Abstract

On the basis of the ⌳ 5 HeϩNϩN three-body model which has successfully been applied to a systematic study of the energy and nucleon halo structure of the Aϭ7 isotriplet hypernuclei, strengths of ␥ transitions in ⌳ 7 Li and ⌳ 7 He are calculated. The new model confirms that the B(E2;5/2 ϩ →1/2 ϩ ) value in ⌳ 7 Li is reduced remarkably in comparison with the corresponding B(E2;3 ϩ →1 ϩ ) in the core nucleus 6 Li. This is due to the gluelike role of the ⌳ particle which induces a contraction of the core nuclear size. It is suggested that a measurement of the 5/2 ϩ →1/2 ϩ E2 transition rate in ⌳ 7 Li ͑ongoing at KEK as E419͒ provides a unique opportunity to derive the hypernuclear size and hence to confirm the size contraction experimentally. The E2 and M 1 transition strengths are also predicted for low-lying states in the hypernucleus ⌳ 7 He whose core nucleus 6 He is known to have a neutron halo. Another prediction is made of much enhanced E2 transitions in ⌳ 7 Li from the 5/2 ϩ and 3/2 ϩ (Tϭ1) states which are expected to have a proton halo structure.

Quadrupole deformation(β,γ)of lightΛhypernuclei in a constrained relativistic mean field model: Shape evolution and shape polarization effect of theLü1, Zhao2, Zhou3 2011Phys. Rev. C

“…The calculation with NLSH-A parameter set also predicts spherical ground states for 13 Λ C and 23 Λ C. In the SHF calculations, the PES of 10 C with a prolate shape is so soft in the γ degree of freedom that one additional Λ drives the shape of 11 Λ C to be oblate [57]. In the present work, 11 Λ C is still prolate with a smaller β compared to 10 C. The addition of a Λ hyperon only makes the PES of 11 Λ C a little softer than that of 10 C. Similar situation holds for 17 Λ C. For the only triaxially deformed carbon nucleus, 18 C, it is observed that the Λ hyperon also makes the PES of 19 Λ C softer and the γ softness increases more towards the prolate direction. Since 20 C is strongly oblate deformed, the addition of a Λ hyperon does not change its shape much.…”

“…The softness of the PES of a nucleus in the γ direction can be measured by E po . For example, it is 0.74 MeV for 10 C and 0.34 MeV for 11 Λ C, which means that the PES of the latter is much softer than the former. However, this difference for 17 Λ C is only 0.06 MeV smaller than that for the corresponding core nucleus, which indicates a very tender change.…”

“…As an impurity in normal nuclei, a hyperon may induce many effects on the core nucleus, such as the shrinkage of the size [10][11][12][13][14], the change of the shape which will be discussed later, the modification of its cluster structure [15], the occurrence of nucleon and hyperon skin or halo [15][16][17], and the shift of neutron drip line to a neutron-rich side [17][18][19].…”

Impurity effects of theΛparticle on the2αcluster states ofBe9andIsaka1, Kimura2 2015Phys. Rev. C22190View full textAdd to dashboardCite

“…For the latter purpose, many theoretical works have been carried out in p-sd-pf shell Λ hypernuclei and revealed structure changes caused by the addition of a Λ particle, so-called impurity effects, such as changes of cluster structures [5][6][7][8][9][10][11][12][13][14] and deformation [15][16][17][18][19][20][21][22]. In particular, p-shell nuclei with pronounced clustering manifest drastic structure changes.…”

Beyond-Mean-Field Approach to Low-Lying Spectra of Λ Hypernuclei

“…The measured energy spectra and electric multipole transition strengths in low-lying states have in fact provided rich information on the Λ-nucleon interaction in nuclear medium as well as on the impurity effect of Λ particle. Many theoretical methods have been developed to investigate the spectroscopy of hypernuclei, such as the cluster model [2,3], the shell model [4], the ab-initio method [5], the antisymmetrized molecular dynamics (AMD) [6], and self-consistent mean-field models [7,8]. Among them, the self-consistent mean-field approach is the only method which can be globally applied from light to heavy hypernuclei.…”