Lifetime measurement of the 260 g.s. at SAMURAI

The ground state of the neutron unbound nucleus26O is speculated to have a lifetime in the pico-second regime. In order to determine the decay lifetime of the26O ground state with high sensitivity and precision, a new method has been applied. The experiment was performed in December 2016 at the Superconducting Analyzer for MUlti-particle from Radio Isotope Beams (SAMURAI) at the Radioactive Isotope Beam Factory (RIBF) at RIKEN. A27F beam was produced in the fragment separator BigRIPS and impinged on a W/Pt target stack where26O was produced. According to the lifetime, the decay of26O happens either in or outside the target. Thus, the velocity difference between the decay neutrons and the fragment24O delivers a characteristic spectrum from which the lifetime can be extracted.