Search for beta-delayed proton emission from $$^{11}$$Be

Abstract

We report on an attempt to reproduce the observation of β −-delayed proton emission from 11 Be through detection of the final state nucleus 10 Be with accelerator mass spectrometry. Twelve samples were collected at the ISOLDE facility at CERN at different separator settings, allowing tests of different sources of contamination to be carried out. The observed amounts of 10 Be per collected 11 Be rule out several contamination sources, but do not agree internally. Formation of BeH molecular ions in the ion source may explain our data, in which case an upper limit of the βp branching ratio of 2.2 • 10 −6 can be derived.

Assessment of the beta-delayed proton decay rate of 11Be

“…Several experiments have been carried out [11][12][13] determining the branching ratio for the beta-delayed proton emission at 1.3 × 10 −5 which corresponds to half-life for this decay branch t Be→βp ≈ 1 × 10 6 s. The phase-space-based estimate for the halo-neutron beta decay carried out in Ref. [13] gives t Be→βp = 2.2 × 10 10 s. A more detailed calculation in Ref [6] gives t Be→βp ∼ 10 8 s. Both estimates suggest half-lives that are several orders of magnitude longer than the observed value.…”

Neutron's Dark Secret

“…However, a recent reanalysis of the [38] data provided an upper limit Br( 11 Be → 10 Be + anything) 2 × 10 −6 [43], which is in contradiction with the experimental result of [41]. Further investigation is needed to determine the cause of this disagreement.…”

$β^-{\rm p}$ and $β^-α$ decay of the $^{11}$Be neutron halo ground state

“…Introduction-A very unusual decay, a β − -delayed proton decay of a neutron-rich nucleus 11 Be, predicted theoretically in [1], was studied in Refs. [2][3][4]. Experimentally, the strength of this decay mode turned out to be unexpectedly high.…”

“…A recent study of Ref. [4] suggests that the branching ratio for the beta-delayed proton decay should be well below that of [3], which adds to the puzzle. Theoretically, the beta-decay rate estimates of Refs.…”

“…In this work, we test the scenarios put forward in Refs. [3,4,8] by analyzing several observables in 11 B, to constrain the value of the β − p branching ratio for the decay of the halo ground state (g.s.) of 11 Be.…”