Search for diphoton decays of an axionlike particle in radiative J/ψ decays

We search for the diphoton decay of a light pseudoscalar axionlike particle, <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>a</a:mi></a:math>, in radiative <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>J</c:mi><c:mo>/</c:mo><c:mi>ψ</c:mi></c:math> decays, using <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:msup><e:mrow><e:mn>10</e:mn></e:mrow><e:mrow><e:mn>10</e:mn></e:mrow></e:msup><e:mtext> </e:mtext><e:mi>J</e:mi><e:mo>/</e:mo><e:mi>ψ</e:mi></e:mrow></e:math> events collected with the BESIII detector. We find no evidence of a signal and set upper limits at the 95% confidence level on the product branching fraction <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi mathvariant="script">B</g:mi><g:mo stretchy="false">(</g:mo><g:mi>J</g:mi><g:mo>/</g:mo><g:mi>ψ</g:mi><g:mo stretchy="false">→</g:mo><g:mi>γ</g:mi><g:mi>a</g:mi><g:mo stretchy="false">)</g:mo><g:mo>×</g:mo><g:mi mathvariant="script">B</g:mi><g:mo stretchy="false">(</g:mo><g:mi>a</g:mi><g:mo stretchy="false">→</g:mo><g:mi>γ</g:mi><g:mi>γ</g:mi><g:mo stretchy="false">)</g:mo></g:math> and the axionlike particle photon coupling constant <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:msub><q:mi>g</q:mi><q:mrow><q:mi>a</q:mi><q:mi>γ</q:mi><q:mi>γ</q:mi></q:mrow></q:msub></q:math> in the ranges of <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:mrow><s:mo stretchy="false">(</s:mo><s:mn>3.7</s:mn><s:mi>–</s:mi><s:mn>48.5</s:mn><s:mo stretchy="false">)</s:mo><s:mo>×</s:mo><s:msup><s:mrow><s:mn>10</s:mn></s:mrow><s:mrow><s:mo>−</s:mo><s:mn>8</s:mn></s:mrow></s:msup></s:mrow></s:math> and <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:mrow><w:mo stretchy="false">(</w:mo><w:mn>2.2</w:mn><w:mi>–</w:mi><w:mn>101.8</w:mn><w:mo stretchy="false">)</w:mo><w:mo>×</w:mo><w:msup><w:mrow><w:mn>10</w:mn></w:mrow><w:mrow><w:mo>−</w:mo><w:mn>4</w:mn></w:mrow></w:msup><w:mtext> </w:mtext><w:mtext> </w:mtext><w:mrow><w:msup><w:mrow><w:mi>GeV</w:mi></w:mrow><w:mrow><w:mo>−</w:mo><w:mn>1</w:mn></w:mrow></w:msup></w:mrow></w:mrow></w:math>, respectively, for <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:mn>0.18</ab:mn><ab:mo>≤</ab:mo><ab:msub><ab:mi>m</ab:mi><ab:mi>a</ab:mi></ab:msub><ab:mo>≤</ab:mo><ab:mn>2.85</ab:mn><ab:mtext> </ab:mtext><ab:mtext> </ab:mtext><ab:mrow><ab:mi>GeV</ab:mi><ab:mo>/</ab:mo></ab:mrow><ab:msup><ab:mi>c</ab:mi><ab:mn>2</ab:mn></ab:msup></ab:math>. These are the most stringent limits to date in this mass region. Published by the American Physical Society 2024