Observation of the Anomalous Shape of X(1840) in J/ψ→γ3(</mml:…

Using a sample of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><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:mrow><a:mn>10</a:mn></a:mrow><a:mrow><a:mn>6</a:mn></a:mrow></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:mrow></a:math> events, which is about 45 times larger than that was previously analyzed, a further investigation on the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:mi>J</e:mi><e:mo>/</e:mo><e:mi>ψ</e:mi><e:mo stretchy="false">→</e:mo><e:mi>γ</e:mi><e:mn>3</e:mn><e:mo stretchy="false">(</e:mo><e:msup><e:mrow><e:mi>π</e:mi></e:mrow><e:mrow><e:mo>+</e:mo></e:mrow></e:msup><e:msup><e:mrow><e:mi>π</e:mi></e:mrow><e:mrow><e:mo>−</e:mo></e:mrow></e:msup><e:mo stretchy="false">)</e:mo></e:mrow></e:math> decay is performed. A significant distortion at <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mrow><j:mn>1.84</j:mn><j:mtext> </j:mtext><j:mtext> </j:mtext><j:mi>GeV</j:mi><j:mo>/</j:mo><j:msup><j:mrow><j:mi>c</j:mi></j:mrow><j:mrow><j:mn>2</j:mn></j:mrow></j:msup></j:mrow></j:math> in the line shape of the <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:mn>3</l:mn><l:mo stretchy="false">(</l:mo><l:msup><l:mi>π</l:mi><l:mo>+</l:mo></l:msup><l:msup><l:mi>π</l:mi><l:mo>−</l:mo></l:msup><l:mo stretchy="false">)</l:mo></l:math> invariant mass spectrum is observed for the first time, which could be resolved by two overlapping resonant structures, <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline"><p:mi>X</p:mi><p:mo stretchy="false">(</p:mo><p:mn>1840</p:mn><p:mo stretchy="false">)</p:mo></p:math> and <t:math xmlns:t="http://www.w3.org/1998/Math/MathML" display="inline"><t:mi>X</t:mi><t:mo stretchy="false">(</t:mo><t:mn>1880</t:mn><t:mo stretchy="false">)</t:mo></t:math>. The new state <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"><x:mi>X</x:mi><x:mo stretchy="false">(</x:mo><x:mn>1880</x:mn><x:mo stretchy="false">)</x:mo></x:math> is observed with a statistical significance larger than <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" display="inline"><bb:mn>10</bb:mn><bb:mi>σ</bb:mi></bb:math>. The mass and width of <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"><db:mi>X</db:mi><db:mo stretchy="false">(</db:mo><db:mn>1880</db:mn><db:mo stretchy="false">)</db:mo></db:math> are determined to be <hb:math xmlns:hb="http://www.w3.org/1998/Math/MathML" display="inline"><hb:mrow><hb:mn>1882.1</hb:mn><hb:mo>±</hb:mo><hb:mn>1.7</hb:mn><hb:mo>±</hb:mo><hb:mn>0.7</hb:mn><hb:mtext> </hb:mtext><hb:mtext> </hb:mtext><hb:mi>MeV</hb:mi><hb:mo>/</hb:mo><hb:msup><hb:mrow><hb:mi>c</hb:mi></hb:mrow><hb:mrow><hb:mn>2</hb:mn></hb:mrow></hb:msup></hb:mrow></hb:math> and <jb:math xmlns:jb="http://www.w3.org/1998/Math/MathML" display="inline"><jb:mrow><jb:mn>30.7</jb:mn><jb:mo>±</jb:mo><jb:mn>5.5</jb:mn><jb:mo>±</jb:mo><jb:mn>2.4</jb:mn><jb:mtext> </jb:mtext><jb:mtext> </jb:mtext><jb:mi>MeV</jb:mi></jb:mrow></jb:math>, respectively, which indicates the existence of a <lb:math xmlns:lb="http://www.w3.org/1998/Math/MathML" display="inline"><lb:mi>p</lb:mi><lb:mover accent="true"><lb:mi>p</lb:mi><lb:mo stretchy="false">¯</lb:mo></lb:mover></lb:math> bound state. Published by the American Physical Society 2024