Two-neutron decay from the $2^+_1$ state of $^6$He

Two-neutron correlations in neutron-rich nuclei have attracted much attention. In paricular, in two-neutron halo nuclei, such two-neutron correlations are characterized as a sptially-correlated $n$-$n$ pair, the so-called dineutron, and have extensively studied from both theoretical and experimental sides. In this contribution, we investigate the dineutron correlation in the excited resonant state of $^6$He. To do it, we calculate the breakup cross section of $^6$He+$^{12}$C reaction at 240 MeV/nucleon, in which the $2^+_1$ resonant state is populated. From the results, we pin down the decay mode of the $2^+_1$ state, and discuss the exsistence of a dineutron in the excited state of $^6$He.