Evidence of a near-threshold resonance in $^{11}$B relevant to the $\beta$-delayed proton emission of $^{11}$Be

A narrow near-threshold proton-emitting resonance (<math display="inline"><msub><mi>E</mi><mi>x</mi></msub><mo>=</mo><mn>11.4</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math>, <math display="inline"><msup><mi>J</mi><mi>π</mi></msup><mo>=</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>+</mo></msup></math>, and <math display="inline"><msub><mi mathvariant="normal">Γ</mi><mi>p</mi></msub><mo>=</mo><mn>4.4</mn><mtext> </mtext><mtext> </mtext><mi>keV</mi></math>) was directly observed in <math display="inline"><mrow><mmultiscripts><mrow><mi mathvariant="normal">B</mi></mrow><mprescripts/><none/><mrow><mn>11</mn></mrow></mmultiscripts></mrow></math> via proton resonance scattering. This resonance was previously inferred in the <math display="inline"><mi>β</mi></math>-delayed proton emission of the neutron halo nucleus <math display="inline"><mrow><mmultiscripts><mrow><mi>Be</mi></mrow><mprescripts/><none/><mrow><mn>11</mn></mrow></mmultiscripts></mrow></math>. The good agreement between both experimental results serves as a ground to confirm the existence of such exotic decay and the particular behavior of weakly bound nuclei coupled to the continuum. <math display="inline"><mrow><mi>R</mi></mrow></math>-matrix analysis shows a sizable partial decay width for both, proton and <math display="inline"><mi>α</mi></math> (<math display="inline"><msub><mi mathvariant="normal">Γ</mi><mi>α</mi></msub><mo>=</mo><mn>11</mn><mtext> </mtext><mtext> </mtext><mi>keV</mi></math>) emission channels.