Evidence of the singly Cabibbo suppressed decay <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi mathvariant="normal">Λ</mml:mi><mml:mi>c</mml:mi><mml:mo>+</mml:mo></mml:msubsup><mml:mo stretchy="false">→</mml:mo><mml:mi>p</mml:mi><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup></mml:math>

Evidence for the singly Cabibbo suppressed decay <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msubsup><a:mi mathvariant="normal">Λ</a:mi><a:mi>c</a:mi><a:mo>+</a:mo></a:msubsup><a:mo stretchy="false">→</a:mo><a:mi>p</a:mi><a:msup><a:mi>π</a:mi><a:mn>0</a:mn></a:msup></a:math> is reported for the first time with a statistical significance of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mn>3.7</e:mn><e:mi>σ</e:mi></e:math> based on <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mn>6.0</g:mn><g:mtext> </g:mtext><g:mtext> </g:mtext><g:msup><g:mi>fb</g:mi><g:mrow><g:mo>−</g:mo><g:mn>1</g:mn></g:mrow></g:msup></g:math> of <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msup><i:mi>e</i:mi><i:mo>+</i:mo></i:msup><i:msup><i:mi>e</i:mi><i:mo>−</i:mo></i:msup></i:math> collision data collected at center-of-mass energies between 4.600 and 4.843 GeV with the BESIII detector at the BEPCII collider. The absolute branching fraction of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msubsup><k:mi mathvariant="normal">Λ</k:mi><k:mi>c</k:mi><k:mo>+</k:mo></k:msubsup><k:mo stretchy="false">→</k:mo><k:mi>p</k:mi><k:msup><k:mi>π</k:mi><k:mn>0</k:mn></k:msup></k:math> is measured to be <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mo stretchy="false">(</o:mo><o:mn>1.5</o:mn><o:msubsup><o:mn>6</o:mn><o:mrow><o:mo>−</o:mo><o:mn>0.58</o:mn></o:mrow><o:mrow><o:mo>+</o:mo><o:mn>0.72</o:mn></o:mrow></o:msubsup><o:mo>±</o:mo><o:mn>0.20</o:mn><o:mo stretchy="false">)</o:mo><o:mo>×</o:mo><o:msup><o:mn>10</o:mn><o:mrow><o:mo>−</o:mo><o:mn>4</o:mn></o:mrow></o:msup></o:math>. Combining with the branching fraction of <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:msubsup><s:mi mathvariant="normal">Λ</s:mi><s:mi>c</s:mi><s:mo>+</s:mo></s:msubsup><s:mo stretchy="false">→</s:mo><s:mi>n</s:mi><s:msup><s:mi>π</s:mi><s:mo>+</s:mo></s:msup></s:math>, <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:mo stretchy="false">(</w:mo><w:mn>6.6</w:mn><w:mo>±</w:mo><w:mn>1.3</w:mn><w:mo stretchy="false">)</w:mo><w:mo>×</w:mo><w:msup><w:mn>10</w:mn><w:mrow><w:mo>−</w:mo><w:mn>4</w:mn></w:mrow></w:msup></w:math>, the ratio of the branching fractions of <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:msubsup><ab:mi mathvariant="normal">Λ</ab:mi><ab:mi>c</ab:mi><ab:mo>+</ab:mo></ab:msubsup><ab:mo stretchy="false">→</ab:mo><ab:mi>n</ab:mi><ab:msup><ab:mi>π</ab:mi><ab:mo>+</ab:mo></ab:msup></ab:math> and <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML" display="inline"><eb:msubsup><eb:mi mathvariant="normal">Λ</eb:mi><eb:mi>c</eb:mi><eb:mo>+</eb:mo></eb:msubsup><eb:mo stretchy="false">→</eb:mo><eb:mi>p</eb:mi><eb:msup><eb:mi>π</eb:mi><eb:mn>0</eb:mn></eb:msup></eb:math> is calculated to be <ib:math xmlns:ib="http://www.w3.org/1998/Math/MathML" display="inline"><ib:msubsup><ib:mn>3.2</ib:mn><ib:mrow><ib:mo>−</ib:mo><ib:mn>1.2</ib:mn></ib:mrow><ib:mrow><ib:mo>+</ib:mo><ib:mn>2.2</ib:mn></ib:mrow></ib:msubsup></ib:math>. As an important input for the theoretical models describing the decay mechanisms of charmed baryons, our result indicates that the nonfactorizable contributions play an essential role and their interference with the factorizable contributions should not be significant. In addition, the absolute branching fraction of <kb:math xmlns:kb="http://www.w3.org/1998/Math/MathML" display="inline"><kb:msubsup><kb:mi mathvariant="normal">Λ</kb:mi><kb:mi>c</kb:mi><kb:mo>+</kb:mo></kb:msubsup><kb:mo stretchy="false">→</kb:mo><kb:mi>p</kb:mi><kb:mi>η</kb:mi></kb:math> is measured to be <ob:math xmlns:ob="http://www.w3.org/1998/Math/MathML" display="inline"><ob:mo stretchy="false">(</ob:mo><ob:mn>1.63</ob:mn><ob:mo>±</ob:mo><ob:mn>0.3</ob:mn><ob:msub><ob:mn>1</ob:mn><ob:mrow><ob:mi>stat</ob:mi></ob:mrow></ob:msub><ob:mo>±</ob:mo><ob:mn>0.1</ob:mn><ob:msub><ob:mn>1</ob:mn><ob:mrow><ob:mi>syst</ob:mi></ob:mrow></ob:msub><ob:mo stretchy="false">)</ob:mo><ob:mo>×</ob:mo><ob:msup><ob:mn>10</ob:mn><ob:mrow><ob:mo>−</ob:mo><ob:mn>3</ob:mn></ob:mrow></ob:msup></ob:math>. Published by the American Physical Society 2024