The first observation of the singly Cabibbo-suppressed <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msubsup><a:mrow><a:mi mathvariant="normal">Ω</a:mi></a:mrow><a:mrow><a:mi>c</a:mi></a:mrow><a:mrow><a:mn>0</a:mn></a:mrow></a:msubsup><a:mo stretchy="false">→</a:mo><a:mrow><a:msup><a:mrow><a:mi mathvariant="normal">Ω</a:mi></a:mrow><a:mrow><a:mo>−</a:mo></a:mrow></a:msup><a:msup><a:mrow><a:mi>K</a:mi></a:mrow><a:mrow><a:mo>+</a:mo></a:mrow></a:msup></a:mrow></a:mrow></a:math> and <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:msubsup><f:mi mathvariant="normal">Ω</f:mi><f:mi>c</f:mi><f:mn>0</f:mn></f:msubsup><f:mo stretchy="false">→</f:mo><f:mrow><f:msup><f:mi mathvariant="normal">Ξ</f:mi><f:mo>−</f:mo></f:msup><f:msup><f:mi>π</f:mi><f:mo>+</f:mo></f:msup></f:mrow></f:math> decays is reported, using proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mrow><k:mn>5.4</k:mn><k:mtext> </k:mtext><k:mtext> </k:mtext><k:msup><k:mrow><k:mi>fb</k:mi></k:mrow><k:mrow><k:mo>−</k:mo><k:mn>1</k:mn></k:mrow></k:msup></k:mrow></k:math>, collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mrow><m:mfrac><m:mrow><m:mi mathvariant="script">B</m:mi><m:mo stretchy="false">(</m:mo><m:msubsup><m:mrow><m:mi mathvariant="normal">Ω</m:mi></m:mrow><m:mrow><m:mi>c</m:mi></m:mrow><m:mrow><m:mn>0</m:mn></m:mrow></m:msubsup><m:mo stretchy="false">→</m:mo><m:mrow><m:msup><m:mrow><m:mi mathvariant="normal">Ω</m:mi></m:mrow><m:mrow><m:mo stretchy="false">−</m:mo></m:mrow></m:msup><m:msup><m:mrow><m:mi>K</m:mi></m:mrow><m:mrow><m:mo stretchy="false">+</m:mo></m:mrow></m:msup></m:mrow><m:mo stretchy="false">)</m:mo></m:mrow><m:mrow><m:mi mathvariant="script">B</m:mi><m:mo stretchy="false">(</m:mo><m:msubsup><m:mrow><m:mi mathvariant="normal">Ω</m:mi></m:mrow><m:mrow><m:mi>c</m:mi></m:mrow><m:mrow><m:mn>0</m:mn></m:mrow></m:msubsup><m:mo stretchy="false">→</m:mo><m:mrow><m:msup><m:mrow><m:mi mathvariant="normal">Ω</m:mi></m:mrow><m:mrow><m:mo stretchy="false">−</m:mo></m:mrow></m:msup><m:msup><m:mrow><m:mi>π</m:mi></m:mrow><m:mrow><m:mo stretchy="false">+</m:mo></m:mrow></m:msup></m:mrow><m:mo stretchy="false">)</m:mo></m:mrow></m:mfrac><m:mo>=</m:mo><m:mo stretchy="false">[</m:mo><m:mn>6.08</m:mn><m:mo>±</m:mo><m:mn>0.51</m:mn><m:mrow><m:mo stretchy="false">(</m:mo><m:mi>stat</m:mi><m:mo stretchy="false">)</m:mo></m:mrow><m:mo>±</m:mo><m:mn>0.40</m:mn><m:mrow><m:mo stretchy="false">(</m:mo><m:mi>syst</m:mi><m:mo stretchy="false">)</m:mo></m:mrow><m:mo stretchy="false">]</m:mo><m:mo>%</m:mo><m:mo>,</m:mo><m:mfrac><m:mrow><m:mi mathvariant="script">B</m:mi><m:mo stretchy="false">(</m:mo><m:msubsup><m:mrow><m:mi mathvariant="normal">Ω</m:mi></m:mrow><m:mrow><m:mi>c</m:mi></m:mrow><m:mrow><m:mn>0</m:mn></m:mrow></m:msubsup><m:mo stretchy="false">→</m:mo><m:mrow><m:msup><m:mrow><m:mi mathvariant="normal">Ξ</m:mi></m:mrow><m:mrow><m:mo stretchy="false">−</m:mo></m:mrow></m:msup><m:msup><m:mrow><m:mi>π</m:mi></m:mrow><m:mrow><m:mo stretchy="false">+</m:mo></m:mrow></m:msup></m:mrow><m:mo stretchy="false">)</m:mo></m:mrow><m:mrow><m:mi mathvariant="script">B</m:mi><m:mo stretchy="false">(</m:mo><m:msubsup><m:mrow><m:mi mathvariant="normal">Ω</m:mi></m:mrow><m:mrow><m:mi>c</m:mi></m:mrow><m:mrow><m:mn>0</m:mn></m:mrow></m:msubsup><m:mo stretchy="false">→</m:mo><m:mrow><m:msup><m:mrow><m:mi mathvariant="normal">Ω</m:mi></m:mrow><m:mrow><m:mo stretchy="false">−</m:mo></m:mrow></m:msup><m:msup><m:mrow><m:mi>π</m:mi></m:mrow><m:mrow><m:mo stretchy="false">+</m:mo></m:mrow></m:msup></m:mrow><m:mo stretchy="false">)</m:mo></m:mrow></m:mfrac><m:mo>=</m:mo><m:mspace linebreak="goodbreak"/><m:mo stretchy="false">[</m:mo><m:mn>15.81</m:mn><m:mo>±</m:mo><m:mn>0.87</m:mn><m:mrow><m:mo stretchy="false">(</m:mo><m:mi>stat</m:mi><m:mo stretchy="false">)</m:mo></m:mrow><m:mo>±</m:mo><m:mn>0.44</m:mn><m:mrow><m:mo stretchy="false">(</m:mo><m:mi>syst</m:mi><m:mo stretchy="false">)</m:mo></m:mrow><m:mo>±</m:mo><m:mn>0.16</m:mn><m:mrow><m:mo stretchy="false">(</m:mo><m:mi>ext</m:mi><m:mo stretchy="false">)</m:mo></m:mrow><m:mo stretchy="false">]</m:mo><m:mo>%</m:mo><m:mo>.</m:mo></m:mrow></m:math> In addition, using the <jc:math xmlns:jc="http://www.w3.org/1998/Math/MathML" display="inline"><jc:msubsup><jc:mi mathvariant="normal">Ω</jc:mi><jc:mi>c</jc:mi><jc:mn>0</jc:mn></jc:msubsup><jc:mo stretchy="false">→</jc:mo><jc:mrow><jc:msup><jc:mi mathvariant="normal">Ω</jc:mi><jc:mo>−</jc:mo></jc:msup><jc:msup><jc:mi>π</jc:mi><jc:mo>+</jc:mo></jc:msup></jc:mrow></jc:math> decay channel, the <oc:math xmlns:oc="http://www.w3.org/1998/Math/MathML" display="inline"><oc:msubsup><oc:mi mathvariant="normal">Ω</oc:mi><oc:mi>c</oc:mi><oc:mn>0</oc:mn></oc:msubsup></oc:math> baryon mass is measured to be <rc:math xmlns:rc="http://www.w3.org/1998/Math/MathML" display="inline"><rc:mrow><rc:mi>M</rc:mi><rc:mo stretchy="false">(</rc:mo><rc:msubsup><rc:mrow><rc:mi mathvariant="normal">Ω</rc:mi></rc:mrow><rc:mrow><rc:mi>c</rc:mi></rc:mrow><rc:mrow><rc:mn>0</rc:mn></rc:mrow></rc:msubsup><rc:mo stretchy="false">)</rc:mo><rc:mo>=</rc:mo><rc:mn>2695.28</rc:mn><rc:mo>±</rc:mo><rc:mn>0.07</rc:mn><rc:mrow><rc:mo stretchy="false">(</rc:mo><rc:mi>stat</rc:mi><rc:mo stretchy="false">)</rc:mo></rc:mrow><rc:mo>±</rc:mo><rc:mn>0.27</rc:mn><rc:mrow><rc:mo stretchy="false">(</rc:mo><rc:mi>syst</rc:mi><rc:mo stretchy="false">)</rc:mo></rc:mrow><rc:mo>±</rc:mo><rc:mn>0.30</rc:mn><rc:mo stretchy="false">(</rc:mo><rc:mi>ext</rc:mi><rc:mo stretchy="false">)</rc:mo><rc:mtext> </rc:mtext><rc:mtext> </rc:mtext><rc:mi>MeV</rc:mi><rc:mo>,</rc:mo></rc:mrow></rc:math> improving the precision of the previous world average by a factor of 4. © 2024 CERN, for the LHCb Collaboration 2024 CERN