Abstract
Background: is expected to have low-lying and states. A first search did not find the [A. Spyrou et al., Phys. Rev. C 84, 044309 (2011)]; however, a resonance in was populated in a second attempt and determined to be unbound with respect to by 1.8(1) MeV with a tentative spin-parity assignment of [J. Snyder et al., Phys. Rev. C 88, 031303(R) (2013)].
Purpose: Search for the predicted state in the three-neutron decay channel.
Method: A two-proton removal reaction from a 55 MeV/u beam was used to populate neutron-unbound states in . The two-, three-, and four-body decay energies of the neutron(s) detected in coincidence were reconstructed using invariant mass spectroscopy. Monte Carlo simulations were performed to extract the resonance and decay properties from the observed spectra.
Results: The low-energy regions of the decay energy spectra can be described with the first excited unbound state of ( MeV, MeV). Including a state in that decays through the first excited state slightly improves the fit at higher energies though the cross section is small.
Conclusions: A component is not needed to describe the data. If the state in is populated, the decay by three-neutron emission through is weak, up to 4 MeV. In the best fit, is unbound with respect to by 1.4 MeV (unbound with respect to by 2.66 MeV) with a strength of .
- Received 9 December 2014
- Revised 30 December 2014
DOI:https://doi.org/10.1103/PhysRevC.91.017304
©2015 American Physical Society