Multichiral facets in symmetry restored states: Five chiral doublet candidates in the even-even nucleus Nd136

Abstract

A triaxial projected shell model including configurations with more than four quasiparticles in the configuration space is developed, and applied to investigate the recently reported five chiral doublets candidates in a single even-even nucleus 136 Nd. The energy spectra and transition probability ratios B(M 1)/B(E2) are reproduced satisfactorily. The configuration mixing along the rotational bands is studied by analyzing the intrinsic composition of the eigenfunctions. The chiral geometry of these nearly degenerate bands is examined by the K plot and the azimuthal plot, and the evolution from the chiral vibration to the static chirality with spin is clearly demonstrated for four pairs of partner bands. From the features in the azimuthal plot, it is difficult to interpret the other candidate as chiral partners. * mengj@pku.edu.cn Chirality is one of the hot topics in biology, chemistry, and physics. The chirality in atomic nuclei was first predicted theoretically by Frauendorf and Meng in 1997 [1]. The predicted topology, the mutually perpendicular angular momenta of the valence protons, valence neutrons, and the core, leads to the so-called spontaneous chiral symmetry breaking in the intrinsic frame. The restoration of the chiral symmetry in the laboratory frame can be manifested by the observation of a pair of nearly degenerate ∆I = 1 bands with the same parity. Within the framework of the adiabatic and configuration fixed constrained triaxial covariant density functional theory (CDFT) [2], a new phenomenon, the existence of multiple chiral doublets (abbreviated as MχD), i.e., more than one pair of chiral doublet bands in one single nucleus has been predicted [3-6]. Many experimental and theoretical efforts have been devoted to study chiral doublets in various mass regions. So far, around 60 pairs of chiral doublets candidates have been established in A ∼ 80 [7, 8], 100 [9-13], 130 [14-20], and 190 [21, 22] mass regions. The observation of chiral bands in different mass regions indicates that nuclear chirality could be universal. The experimental evidences for the MχD were reported in 133 Ce [23], 103 Rh [24], and 78 Br [8] which demonstrate the multiple facets of nuclear chirality. For the detailed experimental status, see the data compilation [25].Theoretically, the chiral doublet bands have been investigated by various approaches, for example, the particle rotor model (PRM) [1,[26][27][28][29], the tilted axis cranking model (TAC) [1,[30][31][32], the TAC approach with the random phase approximation [33] and the collective Hamiltonian [34,35], the interacting boson-fermion-fermion model [16,36,37], the generalized coherent state model [38] and the projected shell model (PSM) [39][40][41]. The PSM carries out the shell model configuration mixing based on Nilsson mean field with the angular momentum projection technique [42]. It has been successfully used to investigate the backbending phenomena [43], superdeformed rotational bands [44], signature inversion [45], and γ bands [46, 47], etc. Recently, this idea ...

Nuclear matrix elements of neutrinoless double-$β$ decay in the triaxial projected shell model

“…The triaxial projected shell model (TPSM) carries out the configuration mixing based on a Nilsson mean field with the angular momentum projection technique [30]. It has been successfully applied to study the nuclear rotational excitations, including the backbending phenomena [31], the superdeformed rotational bands [32], the signature inversion [33], the γ bands [34], and the chiral [35][36][37] and wobbling [38] rotations, etc.…”

“…Refs. [35,37] include triaxial deformation and the configuration interaction induced by the quasiparticle excitations beyond the HFB vacuum, and treat even-even and the odd-odd nuclear systems simultaneously. This provides us an opportunity to study the effects of the triaxial deformation and quasiparticle configuration mixing, and the effects beyond the closure approximation on the NMEs.…”

Pseudospin symmetry and octupole correlations for multiple chiral doublets in 131Ba

“…Theoretically, nuclear chirality has been investigated with many approaches, including the triaxial particle rotor model (PRM) [1,[17][18][19][20][21], the tilted axis cranking (TAC) model [1,[22][23][24][25], the TAC approach with the random phase approximation (TAC+RPA) [26,27] and the collective Hamiltonian (TAC+CH) [28][29][30], the interacting boson-fermion-fermion model (IBFFM) [31], the generalized coherent state model [32] and the projected shell model (PSM) [33][34][35][36][37].…”

Dynamics of rotation in chiral nuclei

“…This is a well-known deficiency of the mean-field solution when it spontaneously breaks a symmetry [2]. Consequently, the random-phase approximation method [17,34], the collective Hamiltonian method [35,36], and the projected shell model [37][38][39][40] have been developed to describe the chiral excitations. However, these approaches are based on single-particle potentials combined with either the schematic single-j Hamiltonian [36] or the pairing plus quadrupole-quadrupole model [41].…”