Shape evolution in neutron-rich $A \sim 140$ nuclei beyond the doubly-magic nucleus $^{132}$Sn

Study for the shape evolution enables us to disentangle competition between spherical (single-particle like) shape and deformed (collective-like) shape as a function of neutron number. Neutron-rich nuclei in the northeast region of the doubly-magic $^{132}$Sn locates in one of the best mass region where a variety of collective modes, not only prolate deformation but also octupole collectivity, are expected to appear. These neutron-rich $A$$\sim$140 nuclei were produced by using in-flight fission reaction of the 345 MeV/u $^{238}$U$^{86+}$ beam at RIKEN RI Beam Factory. This experiment was performed in the framework of the EURICA (EUroball RIken Cluster Array) project based on the highly-efficient $\beta$- and isomer- decay spectroscopy methods. Around 20 extremely neutron-rich nuclei with $Z$=51-55 have been studied in this work. New isomers with half lives of longer than hundreds ns were found in some nuclei, such as the neutron-rich Cs isotopes. Also, preliminary results for the $\beta$ decay of neutron-rich I and Xe isotopes have been obtained. Systematic change of the shape evolution for these neutron-rich isotopes will be discussed.