Coexistence of cluster structure and superdeformation in $^{44}$Ti studied with deformed-basis antisymmetrized molecular dynamics

The nucleus $^{44}$Ti has low-lying levels of various kinds of mutually very different nuclear structure displaying the richness of the nuclear many-body dynamics. It is shown that the deformed-basis antisymmetrized molecular dynamics by the use of the Gogny D1S force reproduces successfully and unifiedly two types of coexistence phenomena in $^{44}$Ti. Namely, on one hand, the coexistence of the mean field structure and the cluster structure is confirmed by verifying the normally deformed structure of the $K^\pi$=$3^-_1$ band with a 1-particle-jump intrinsic configuration and the $\alpha + ^{40}$Ca cluster structure of the $K^\pi$=$0^-_2$ band. The mixed character of the mean-field-like structure and the $\alpha + ^{40}$Ca cluster structure of the ground band is also shown. On the other hand, the coexistence of the normal deformed mean field and the superdeformed mean field is confirmed by verifying the triaxial superdeformation of the $K^\pi$=$0_2^+$ band and the $K^\pi$=$2^+_1$ band which has a 4-particle-jump intrinsic configuration. Good reproduction of the experimental data is shown for many kinds of quantities including the energy spectra, electric transition rates, alpha spectroscopic factors. Preliminary discussions are given on the existence of hyperdeformed excited states, the relation between superdeformation and clustering and so on.