Two-Neutron Decay from the Ground State of $^{26}$O

The study of $^{26}$O is important to understand the behavior and properties of neutron-rich heavy oxygen isotopes. Recent experiments have indicated that $^{24}$O is bound and the tests have failed to find bound states of $^{25}$O and $^{26}$O. Unstable $^{26}$O decays to stable $^{24}$O by emitting two neutrons ($^{26}$O$\rightarrow^{24}$O + 2n) rather than decaying via $^{25}$O, which is neutron unbound with a {\it 1n} separation energy of 770 keV. An investigation of $^{26}$O was conducted at the National Superconducting Cyclotron Laboratory, which possesses the capability to produce rare isotope beams and detect neutrons with an efficiency of about 70\% with the MoNA detector. Production of $^{26}$O was done by one-proton removal from a $^{27}$F beam with an energy of 82 MeV/u impending on a 705 mg/cm$^2$ Be target. Coincidence of the two neutrons with $^{24}$O was measured for four-vector momentum event reconstruction, allowing extraction of the invariant mass of $^{26}$O.