Abstract
<jats:p> Using <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mrow> <a:mo>(</a:mo> <a:mn>1.0087</a:mn> <a:mo>±</a:mo> <a:mn>0.0044</a:mn> <a:mo>)</a:mo> </a:mrow> <a:mo>×</a:mo> <a:msup> <a:mn>10</a:mn> <a:mn>10</a:mn> </a:msup> </a:mrow> <a:mo> </a:mo> <a:mrow> <a:mi>J</a:mi> <a:mo>/</a:mo> <a:mi>ψ</a:mi> </a:mrow> </a:math> events collected with the BESIII detector at the BEPCII storage ring, the reactions <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:msup> <b:mi mathvariant="normal">Σ</b:mi> <b:mo>+</b:mo> </b:msup> <b:mi>n</b:mi> <b:mo>→</b:mo> <b:mi mathvariant="normal">Λ</b:mi> <b:mi>p</b:mi> </b:mrow> </b:math> and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:msup> <e:mi mathvariant="normal">Σ</e:mi> <e:mo>+</e:mo> </e:msup> <e:mi>n</e:mi> <e:mo>→</e:mo> <e:msup> <e:mi mathvariant="normal">Σ</e:mi> <e:mn>0</e:mn> </e:msup> <e:mi>p</e:mi> </e:mrow> </e:math> are studied, where the <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:msup> <h:mi mathvariant="normal">Σ</h:mi> <h:mo>+</h:mo> </h:msup> </h:math> baryon is produced in the process <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"> <j:mrow> <j:mi>J</j:mi> <j:mo>/</j:mo> <j:mi>ψ</j:mi> <j:mo>→</j:mo> <j:msup> <j:mi mathvariant="normal">Σ</j:mi> <j:mo>+</j:mo> </j:msup> <j:msup> <j:mover accent="true"> <j:mi mathvariant="normal">Σ</j:mi> <j:mo>¯</j:mo> </j:mover> <j:mo>−</j:mo> </j:msup> </j:mrow> </j:math> and the neutron is a component of the <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"> <n:mmultiscripts> <n:mi>Be</n:mi> <n:mprescripts/> <n:none/> <n:mn>9</n:mn> </n:mmultiscripts> <n:mo>,</n:mo> <n:mo> </n:mo> <n:mmultiscripts> <n:mi mathvariant="normal">C</n:mi> <n:mprescripts/> <n:none/> <n:mn>12</n:mn> </n:mmultiscripts> </n:math> , and <p:math xmlns:p="http://www.w3.org/1998/Math/MathML"> <p:mmultiscripts> <p:mi>Au</p:mi> <p:mprescripts/> <p:none/> <p:mn>197</p:mn> </p:mmultiscripts> </p:math> nuclei in the beam pipe. Clear signals of these two reactions are observed for the first time. Their cross sections are measured to be <q:math xmlns:q="http://www.w3.org/1998/Math/MathML"> <q:mrow> <q:mi>σ</q:mi> <q:mrow> <q:mo>(</q:mo> <q:msup> <q:mi mathvariant="normal">Σ</q:mi> <q:mo>+</q:mo> </q:msup> <q:mo>+</q:mo> <q:mmultiscripts> <q:mi>Be</q:mi> <q:mprescripts/> <q:none/> <q:mn>9</q:mn> </q:mmultiscripts> <q:mo>→</q:mo> <q:mi mathvariant="normal">Λ</q:mi> <q:mo>+</q:mo> <q:mi>p</q:mi> <q:mo>+</q:mo> <q:mi>X</q:mi> <q:mo>)</q:mo> </q:mrow> <q:mo>=</q:mo> <q:mrow> <q:mo>(</q:mo> <q:mn>45.2</q:mn> <q:mo>±</q:mo> <q:mn>12</q:mn> <q:mo>.</q:mo> <q:msub> <q:mn>1</q:mn> <q:mi>stat</q:mi> </q:msub> <q:mo>±</q:mo> <q:mn>7</q:mn> <q:mo>.</q:mo> <q:msub> <q:mn>2</q:mn> <q:mi>sys</q:mi> </q:msub> <q:mo>)</q:mo> </q:mrow> </q:mrow> </q:math> mb and <t:math xmlns:t="http://www.w3.org/1998/Math/MathML"> <t:mrow> <t:mi>σ</t:mi> <t:mrow> <t:mo>(</t:mo> <t:msup> <t:mi mathvariant="normal">Σ</t:mi> <t:mo>+</t:mo> </t:msup> <t:mo>+</t:mo> <t:mmultiscripts> <t:mi>Be</t:mi> <t:mprescripts/> <t:none/> <t:mn>9</t:mn> </t:mmultiscripts> <t:mo>→</t:mo> <t:msup> <t:mi mathvariant="normal">Σ</t:mi> <t:mn>0</t:mn> </t:msup> <t:mo>+</t:mo> <t:mi>p</t:mi> <t:mo>+</t:mo> <t:mi>X</t:mi> <t:mo>)</t:mo> </t:mrow> <t:mo>=</t:mo> <t:mrow> <t:mo>(</t:mo> <t:mn>29.8</t:mn> <t:mo>±</t:mo> <t:mn>9</t:mn> <t:mo>.</t:mo> <t:msub> <t:mn>7</t:mn> <t:mi>stat</t:mi> </t:msub> <t:mo>±</t:mo> <t:mn>6</t:mn> <t:mo>.</t:mo> <t:msub> <t:mn>9</t:mn> <t:mi>sys</t:mi> </t:msub> <t:mo>)</t:mo> </t:mrow> </t:mrow> </t:math> mb for a <w:math xmlns:w="http://www.w3.org/1998/Math/MathML"> <w:msup> <w:mi mathvariant="normal">Σ</w:mi> <w:mo>+</w:mo> </w:msup> </w:math> average momentum of <y:math xmlns:y="http://www.w3.org/1998/Math/MathML"> <y:mrow> <y:mn>0.992</y:mn> <y:mspace width="0.28em"/> <y:mi>GeV</y:mi> <y:mo>/</y:mo> <y:mi>c</y:mi> </y:mrow> </y:math> , within a range of <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML"> <ab:mrow> <ab:mo>±</ab:mo> <ab:mn>0.015</ab:mn> <ab:mspace width="0.28em"/> <ab:mi>GeV</ab:mi> <ab:mo>/</ab:mo> <ab:mi>c</ab:mi> </ab:mrow> </ab:math> , where <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML"> <cb:mi>X</cb:mi> </cb:math> represents the residual nucleus. This is the first study of <db:math xmlns:db="http://www.w3.org/1998/Math/MathML"> <db:msup> <db:mi mathvariant="normal">Σ</db:mi> <db:mo>+</db:mo> </db:msup> </db:math> -nucleon scattering at an electron-positron collider. The measured results serve as a significant element in enhancing the comprehensive understanding of hyperon-nucleon interactions, and also constitute an important factor in resolving the “hyperon puzzle” of neutron stars. </jats:p>