Three-body correlations in the ground-state decay of 26O

Background: Theoretical calculations have shown that the energy and angular correlations in the three-body decay of the two-neutron unbound O-26 can provide information on the ground-state wave function, which has been predicted to have a dineutron configuration and 2n halo structure. Purpose: To use the experimentally measured three-body correlations to gain insight into the properties of 26O, including the decay mechanism and ground-state resonance energy. Method: O-26 was produced in a one-proton knockout reaction from F-27 and the O-24 + n + n decay products were measured using the MoNA-Sweeper setup. The three-body correlations from the O-26 ground-state resonance decay were extracted. The experimental results were compared to Monte Carlo simulations in which the resonance energy and decay mechanism were varied. Results: The measured three-body correlations were well reproduced by the Monte Carlo simulations but were not sensitive to the decay mechanism due to the experimental resolutions. However, the three-body correlations were found to be sensitive to the resonance energy of O-26. A 1 sigma upper limit of 53 keV was extracted for the ground-state resonance energy of O-26. Conclusions: Future attempts to measure the three-body correlations from the ground-state decay of O-26 will be very challenging due to the need for a precise measurement of the O-24 momentum at the reaction point in the target.