Amplitude analysis and branching fraction measurement of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>J</mml:mi> <mml:mo>/</mml:mo> <mml:mi>ψ</mml:mi> <mml:mo stretchy="false">→</mml:mo> <mml:mi mathvariant="norm

Based on a sample of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mo stretchy="false">(</a:mo> <a:mn>10087</a:mn> <a:mo>±</a:mo> <a:mn>44</a:mn> <a:mo stretchy="false">)</a:mo> <a:mo>×</a:mo> <a:msup> <a:mn>10</a:mn> <a:mn>6</a:mn> </a:msup> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi>J</a:mi> <a:mo>/</a:mo> <a:mi>ψ</a:mi> </a:math> events collected with the BESIII detector, a partial-wave analysis of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi>J</e:mi> <e:mo>/</e:mo> <e:mi>ψ</e:mi> <e:mo stretchy="false">→</e:mo> <e:mi mathvariant="normal">Λ</e:mi> <e:msup> <e:mover accent="true"> <e:mi mathvariant="normal">Σ</e:mi> <e:mo stretchy="false">¯</e:mo> </e:mover> <e:mn>0</e:mn> </e:msup> <e:mi>η</e:mi> <e:mo>+</e:mo> <e:mi mathvariant="normal">c</e:mi> <e:mo>.</e:mo> <e:mi mathvariant="normal">c</e:mi> <e:mo>.</e:mo> </e:math> is performed for the first time. The dominant contributions are found to be excited <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"> <n:mi mathvariant="normal">Λ</n:mi> </n:math> states with <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"> <q:msup> <q:mi>J</q:mi> <q:mi>P</q:mi> </q:msup> <q:mo>=</q:mo> <q:mn>1</q:mn> <q:mo>/</q:mo> <q:msup> <q:mn>2</q:mn> <q:mo>−</q:mo> </q:msup> </q:math> and <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"> <s:msup> <s:mi>J</s:mi> <s:mi>P</s:mi> </s:msup> <s:mo>=</s:mo> <s:mn>1</s:mn> <s:mo>/</s:mo> <s:msup> <s:mn>2</s:mn> <s:mo>+</s:mo> </s:msup> </s:math> in the <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"> <u:mi>η</u:mi> <u:mi mathvariant="normal">Λ</u:mi> </u:math> mass spectra. The measured masses and widths are <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"> <x:mi>M</x:mi> <x:mo>=</x:mo> <x:mn>1668.8</x:mn> <x:mo>±</x:mo> <x:mn>3.1</x:mn> <x:mo>±</x:mo> <x:mn>21.2</x:mn> <x:mtext> </x:mtext> <x:mtext> </x:mtext> <x:mi>MeV</x:mi> <x:mo>/</x:mo> <x:msup> <x:mi>c</x:mi> <x:mn>2</x:mn> </x:msup> </x:math> and <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"> <z:mi mathvariant="normal">Γ</z:mi> <z:mo>=</z:mo> <z:mn>52.7</z:mn> <z:mo>±</z:mo> <z:mn>4.2</z:mn> <z:mo>±</z:mo> <z:mn>17.8</z:mn> <z:mtext> </z:mtext> <z:mtext> </z:mtext> <z:mi>MeV</z:mi> </z:math> for the <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML" display="inline"> <cb:mi mathvariant="normal">Λ</cb:mi> <cb:mo stretchy="false">(</cb:mo> <cb:mn>1670</cb:mn> <cb:mo stretchy="false">)</cb:mo> </cb:math> , and <hb:math xmlns:hb="http://www.w3.org/1998/Math/MathML" display="inline"> <hb:mi>M</hb:mi> <hb:mo>=</hb:mo> <hb:mn>1881.5</hb:mn> <hb:mo>±</hb:mo> <hb:mn>16.5</hb:mn> <hb:mo>±</hb:mo> <hb:mn>20.3</hb:mn> <hb:mtext> </hb:mtext> <hb:mtext> </hb:mtext> <hb:mi>MeV</hb:mi> <hb:mo>/</hb:mo> <hb:msup> <hb:mi>c</hb:mi> <hb:mn>2</hb:mn> </hb:msup> </hb:math> and <jb:math xmlns:jb="http://www.w3.org/1998/Math/MathML" display="inline"> <jb:mi mathvariant="normal">Γ</jb:mi> <jb:mo>=</jb:mo> <jb:mn>82.4</jb:mn> <jb:mo>±</jb:mo> <jb:mn>18.2</jb:mn> <jb:mo>±</jb:mo> <jb:mn>8.9</jb:mn> <jb:mtext> </jb:mtext> <jb:mtext> </jb:mtext> <jb:mi>MeV</jb:mi> </jb:math> for the <mb:math xmlns:mb="http://www.w3.org/1998/Math/MathML" display="inline"> <mb:mi mathvariant="normal">Λ</mb:mi> <mb:mo stretchy="false">(</mb:mo> <mb:mn>1810</mb:mn> <mb:mo stretchy="false">)</mb:mo> </mb:math> , respectively. The branching fraction is determined to be <rb:math xmlns:rb="http://www.w3.org/1998/Math/MathML" display="inline"> <rb:mi mathvariant="script">B</rb:mi> <rb:mo stretchy="false">(</rb:mo> <rb:mi>J</rb:mi> <rb:mo>/</rb:mo> <rb:mi>ψ</rb:mi> <rb:mo stretchy="false">→</rb:mo> <rb:mi mathvariant="normal">Λ</rb:mi> <rb:msup> <rb:mover accent="true"> <rb:mi mathvariant="normal">Σ</rb:mi> <rb:mo stretchy="false">¯</rb:mo> </rb:mover> <rb:mn>0</rb:mn> </rb:msup> <rb:mi>η</rb:mi> <rb:mo>+</rb:mo> <rb:mi mathvariant="normal">c</rb:mi> <rb:mo>.</rb:mo> <rb:mi mathvariant="normal">c</rb:mi> <rb:mo>.</rb:mo> <rb:mo stretchy="false">)</rb:mo> <rb:mo>=</rb:mo> <rb:mo stretchy="false">(</rb:mo> <rb:mn>3.44</rb:mn> <rb:mo>±</rb:mo> <rb:mn>0.11</rb:mn> <rb:mo>±</rb:mo> <rb:mn>0.13</rb:mn> <rb:mo stretchy="false">)</rb:mo> <rb:mo>×</rb:mo> <rb:msup> <rb:mn>10</rb:mn> <rb:mrow> <rb:mo>−</rb:mo> <rb:mn>5</rb:mn> </rb:mrow> </rb:msup> </rb:math> . The first uncertainties are statistical and the second systematic.