Parity reversion in ¹²_Λ Be

The spectrum of $^{12}_\Lambda$Be is studied by an extended version of antisymmetrized molecular dynamics for hypernuclei. The result predicts the positive-parity ground state of $^{12}_\Lambda$Be that is reverted to the normal one by the impurity effect of $\Lambda$ particle. The reversion of the parity is due to the difference of $\Lambda$ binding energy in the positive- and negative-parity states that originates in the difference of $\alpha$ clustering and deformation.