A Spectroscopic Study of the 21 Ne Hypernucleus

Abstract

985A study of :',lNe hypernucleus is carried out within the framework of a+ 16 0+A cluster model dynamics. The positive and negative parity states are analyzed in detail by calculating energy spectra, r. m. s. radii, B(E2) values and reduced widths to the 2°Ne+A, a+~70 and ~He+160 channels. The obtained states constitute various kinds of rotational bands. Emphasis of discussion is put on the structure characteristics of these rotational bands and on the glue·like effects generated by a A particle coupled with the nuclear core.coupling type energy spectra. The'Iatter feature is characteristic of the prolate deformation of the nucleus (A + B). If the deformation is oblate, the situation changes to a certain extent. Among these states we find some "genuinely hypernuclear states" which can never be realized in ordinary nuclei because of the Pauli exclusion principle. 8 ),9),12)-14) How such coupling feature will be beyond the P-shell hypernuc1eus is an interesting problem. 12 )In this paper we intend to study ~1Ne as a typical (sd)-shell hypernucleus. The 2°Ne nucleus has been extensively investigated in terms of the cluster model. For the later discussion, the observed energy levels of 2°N e are classified into six rotational bands shown in the left side of Fig. 1 according to the literatures. 16 )-18) The simplest di-cluster a+ 16 0 model successfully describes the ground K"=O+ band, the fourth K"=O+ band (the by guest on March 30, 2015 http://ptp.oxfordjournals.org/ Downloaded from

Deformation of hypernuclei studied with antisymmetrized molecular dynamics

“…In all cases, s reduces quadrupole deformation. This is consistent with cluster model calculations [22,27] and (relativistic) mean-field calculations [3][4][5] that have demonstrated the reduction of β by s . On the other hand, it is found that p increases β.…”

“…Our result shows the opposite trend to their result: Since the positive-parity state is more deformed than the negative-parity state, the binding of s is weaker when it is coupled to the negative-parity state. This trend is common to other calculations, including the cluster model calculation for 21 Ne [22]. However, AMD fails to reproduce the small excitation energy of the negative-parity state and does not have prominent α + 15 O clustering; both of these results are mainly due to the lack of angular momentum projection and the GCM calculation.…”

“…On the contrary, p is more deeply bound to the negative-parity state. Since the number of nucleons in 20 Ne is large enough to bound p , we can expect that the addition of will generate a variety of bound rotational bands in 21 Ne, as discussed by Yamada et al [22]. We will discuss 21 Ne in detail in the forthcoming paper.…”

“…Since the normal forms of these nuclei have a variety of structures, such as a coexistence of shell and cluster structure [14][15][16] and novel exotic clustering [17][18][19][20][21], there must be many interesting phenomena peculiar to hypernuclei to be found. Indeed, several pioneering works have predicted exotic structures in sd-shell hypernuclei, such as parity inversion in 20 Ne [7] and various rotational bands in 21 Ne [22]. These works have been based on rather limited knowledge of the N interaction.…”

Excited states with Λ hyperon in p-orbit in MgΛ25

“…For example, the parity inversion of the 20 Λ Ne ground state was predicted [5]. In 21 Λ Ne, it was predicted that the Λ hyperon generates various α+ 16 O +Λ cluster states and mean-field-like states [6,7]. The difference between these structures leads to the difference in the Λ binding energies and the reduction of the B(E2) [7].…”