Search for unbound Be 15 states in the 3n+ Be 12 channel

A. N. Kuchera, A. Spyrou, J. K. Smith, T. Baumann, G. Christian, P. A. Deyoung, J. E. Finck, N. Frank, M. D. Jones, Z. Kohley, S. Mosby, W. A. Peters, M. Thoennessen

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9 Scopus citations

Abstract

Background: Be15 is expected to have low-lying 3/2+ and 5/2+ states. A first search did not find the 3/2+ [A. Spyrou et al., Phys. Rev. C 84, 044309 (2011)PRVCAN0556-281310.1103/PhysRevC.84.044309]; however, a resonance in Be15 was populated in a second attempt and determined to be unbound with respect to Be14 by 1.8(1) MeV with a tentative spin-parity assignment of 5/2+ [J. Snyder et al., Phys. Rev. C 88, 031303(R) (2013)PRVCAN0556-281310.1103/PhysRevC.88.031303]. Purpose: Search for the predicted 15Be3/2+ state in the three-neutron decay channel. Method: A two-proton removal reaction from a 55 MeV/u 17C beam was used to populate neutron-unbound states in Be15. The two-, three-, and four-body decay energies of the 12Be+ 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 Be14 (Ex=1.54 MeV, Er=0.28 MeV). Including a state in Be15 that decays through the first excited Be14 state slightly improves the fit at higher energies though the cross section is small. Conclusions: A Be15 component is not needed to describe the data. If the 3/2+ state in Be15 is populated, the decay by three-neutron emission through Be14 is weak, ≤11% up to 4 MeV. In the best fit, Be15 is unbound with respect to Be12 by 1.4 MeV (unbound with respect to Be14 by 2.66 MeV) with a strength of 7%.

Original languageEnglish (US)
Article number017304
JournalPhysical Review C - Nuclear Physics
Volume91
Issue number1
DOIs
StatePublished - Jan 28 2015
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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