Decay study of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Be</mml:mi><mml:mprescripts/><mml:none/><mml:mn>11</mml:mn></mml:mmultiscripts></mml:math> with an optical time-projection chamber

The <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>β</a:mi></a:math> decay of one-neutron halo nucleus <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mmultiscripts><b:mi>Be</b:mi><b:mprescripts/><b:none/><b:mn>11</b:mn></b:mmultiscripts></b:math> was investigated using the Warsaw Optical Time Projection Chamber (OTPC) detector to measure <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mi>β</c:mi></c:math>-delayed charged particles. The results of two experiments are reported. In the first one, carried out in LNS Catania, the absolute branching ratio for <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mi>β</d:mi></d:math>-delayed <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mi>α</e:mi></e:math> emission was measured by counting incoming <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mmultiscripts><f:mi>Be</f:mi><f:mprescripts/><f:none/><f:mn>11</f:mn></f:mmultiscripts></f:math> ions stopped in the detector and the observed decays with the emission of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mi>α</g:mi></g:math> particle. The result of 3.27(46)% is in good agreement with the literature value. In the second experiment, performed at the HIE-ISOLDE facility at CERN, bunches containing several hundreds of <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:mmultiscripts><h:mi>Be</h:mi><h:mprescripts/><h:none/><h:mn>11</h:mn></h:mmultiscripts></h:math> ions were implanted into the OTPC detector followed by the detection of decays with the emission of charged particles. The energy spectrum of <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"><i:mi>β</i:mi></i:math>-delayed <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"><j:mi>α</j:mi></j:math> particles was determined in the full energy range. It was analyzed in the R-matrix framework and was found to be consistent with the literature. The best description of the spectrum was obtained assuming that the two <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:mn>3</k:mn><k:mo>/</k:mo><k:msup><k:mn>2</k:mn><k:mo>+</k:mo></k:msup></k:mrow></k:math> and one <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"><l:mrow><l:mn>1</l:mn><l:mo>/</l:mo><l:msup><l:mn>2</l:mn><l:mo>+</l:mo></l:msup></l:mrow></l:math> states in <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"><m:mmultiscripts><m:mi mathvariant="normal">B</m:mi><m:mprescripts/><m:none/><m:mn>11</m:mn></m:mmultiscripts></m:math> are involved in the transition. The search for <o:math xmlns:o="http://www.w3.org/1998/Math/MathML"><o:mi>β</o:mi></o:math>-delayed emission of protons was undertaken. Only the upper limit for the branching ratio for this process of <p:math xmlns:p="http://www.w3.org/1998/Math/MathML"><p:mrow><p:mrow><p:mo>(</p:mo><p:mn>2.2</p:mn><p:mo>±</p:mo><p:mn>0</p:mn><p:mo>.</p:mo><p:msub><p:mn>6</p:mn><p:mi>stat</p:mi></p:msub><p:mo>±</p:mo><p:mn>0</p:mn><p:mo>.</p:mo><p:msub><p:mn>6</p:mn><p:mi>sys</p:mi></p:msub><p:mo>)</p:mo></p:mrow><p:mo>×</p:mo><p:msup><p:mn>10</p:mn><p:mrow><p:mo>−</p:mo><p:mn>6</p:mn></p:mrow></p:msup></p:mrow></p:math> could be determined. This value is in conflict with the result published by Ayyad [] but does agree with the limit reported by Riisager []. Published by the American Physical Society 2024