Triaxial quadrupole deformation dynamics in sd-shell nuclei around 26Mg

Large-amplitude dynamics of axial and triaxial quadrupole deformation in Mg-24,Mg-26, Ne-24, and Si-28 is investigated on the basis of the quadrupole collective Hamiltonian constructed with the use of the constrained Hartree-Fock-Bogoliubov plus the local quasiparticle random-phase approximation method. The calculation reproduces well properties of the ground rotational bands, and beta and gamma vibrations in Mg-24 and Si-28. The gamma softness in the collective states of Mg-26 and Ne-24 are discussed. Contributions of the neutrons and protons to the transition properties are also analyzed in connection with the large-amplitude quadrupole dynamics.