First observation of the Λb0→Λc+<…

The <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msubsup><a:mrow><a:mi mathvariant="normal">Λ</a:mi></a:mrow><a:mrow><a:mi>b</a:mi></a:mrow><a:mrow><a:mn>0</a:mn></a:mrow></a:msubsup><a:mo stretchy="false">→</a:mo><a:msubsup><a:mrow><a:mi mathvariant="normal">Λ</a:mi></a:mrow><a:mrow><a:mi>c</a:mi></a:mrow><a:mrow><a:mo>+</a:mo></a:mrow></a:msubsup><a:msubsup><a:mrow><a:mi>D</a:mi></a:mrow><a:mrow><a:mi>s</a:mi></a:mrow><a:mrow><a:mo>−</a:mo></a:mrow></a:msubsup><a:msup><a:mrow><a:mi>K</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:math> decay is observed for the first time using the data sample from proton-proton collisions recorded at a center-of-mass energy of 13 TeV with the LHCb detector, corresponding to an integrated luminosity of <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mn>6</f:mn><f:mtext> </f:mtext><f:mtext> </f:mtext><f:msup><f:mi>fb</f:mi><f:mrow><f:mo>−</f:mo><f:mn>1</f:mn></f:mrow></f:msup></f:math>. The ratio of branching fraction to that of <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:msubsup><h:mi mathvariant="normal">Λ</h:mi><h:mi>b</h:mi><h:mn>0</h:mn></h:msubsup><h:mo stretchy="false">→</h:mo><h:msubsup><h:mi mathvariant="normal">Λ</h:mi><h:mi>c</h:mi><h:mo>+</h:mo></h:msubsup><h:msubsup><h:mi>D</h:mi><h:mi>s</h:mi><h:mo>−</h:mo></h:msubsup></h:math> decays is measured as <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mn>0.0141</m:mn><m:mo>±</m:mo><m:mn>0.0019</m:mn><m:mo>±</m:mo><m:mn>0.0012</m:mn></m:math>, where the first uncertainty is statistical and the second systematic. A search for hidden-charm pentaquarks with strangeness is performed in the <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:msubsup><o:mi mathvariant="normal">Λ</o:mi><o:mi>c</o:mi><o:mo>+</o:mo></o:msubsup><o:msubsup><o:mi>D</o:mi><o:mi>s</o:mi><o:mo>−</o:mo></o:msubsup></o:math> system. No evidence is found, and upper limits on the production ratio of <r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline"><r:msub><r:mi>P</r:mi><r:mrow><r:mi>c</r:mi><r:mover accent="true"><r:mi>c</r:mi><r:mo stretchy="false">¯</r:mo></r:mover><r:mi>s</r:mi></r:mrow></r:msub><r:mo stretchy="false">(</r:mo><r:mn>4338</r:mn><r:msup><r:mo stretchy="false">)</r:mo><r:mn>0</r:mn></r:msup></r:math> and <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"><x:msub><x:mi>P</x:mi><x:mrow><x:mi>c</x:mi><x:mover accent="true"><x:mi>c</x:mi><x:mo stretchy="false">¯</x:mo></x:mover><x:mi>s</x:mi></x:mrow></x:msub><x:mo stretchy="false">(</x:mo><x:mn>4459</x:mn><x:msup><x:mo stretchy="false">)</x:mo><x:mn>0</x:mn></x:msup></x:math> pentaquarks relative to the <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"><db:msubsup><db:mi mathvariant="normal">Λ</db:mi><db:mi>c</db:mi><db:mo>+</db:mo></db:msubsup><db:msubsup><db:mi>D</db:mi><db:mi>s</db:mi><db:mo>−</db:mo></db:msubsup></db:math> final state are set at the 95% confidence level as 0.12 and 0.20, respectively.