Measurement of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>−</mml:mo> </mml:msup> <mml:mo stretchy="false">→</mml:mo> <mml:mi>η</mml:mi> <mml:mi>γ</mml:mi> </mml:math> cross section near the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>ϕ</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1020</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:math> resonance with the SND detector

<jats:p> In the experiment with the SND at the VEPP- <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mn>2000</a:mn> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:msup> <a:mi>e</a:mi> <a:mo>+</a:mo> </a:msup> <a:msup> <a:mi>e</a:mi> <a:mo>−</a:mo> </a:msup> </a:math> collider, the <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msup> <c:mi>e</c:mi> <c:mo>+</c:mo> </c:msup> <c:msup> <c:mi>e</c:mi> <c:mo>−</c:mo> </c:msup> <c:mo stretchy="false">→</c:mo> <c:mi>η</c:mi> <c:mi>γ</c:mi> </c:math> cross section is measured in the energy range <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:mi>E</f:mi> <f:mo>=</f:mo> <f:mn>980</f:mn> <f:mi>–</f:mi> <f:mn>1060</f:mn> <f:mtext> </f:mtext> <f:mtext> </f:mtext> <f:mi>MeV</f:mi> </f:math> . The measurement is carried out in the <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"> <h:mi>η</h:mi> <h:mo stretchy="false">→</h:mo> <h:mn>2</h:mn> <h:mi>γ</h:mi> </h:math> decay mode. Data with an integrated luminosity of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:mn>73</k:mn> <k:mtext> </k:mtext> <k:mtext> </k:mtext> <k:msup> <k:mi>pb</k:mi> <k:mrow> <k:mo>−</k:mo> <k:mn>1</k:mn> </k:mrow> </k:msup> </k:math> collected in 2018 and 2024 are used in the analysis. The measured cross section is the most accurate to date and is higher compared to other measurements. From the fit to the cross section data with the vector meson dominance model, the value of the product of the branching fractions <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:mi>B</m:mi> <m:mo stretchy="false">(</m:mo> <m:mi>ϕ</m:mi> <m:mo stretchy="false">→</m:mo> <m:msup> <m:mi>e</m:mi> <m:mo>+</m:mo> </m:msup> <m:msup> <m:mi>e</m:mi> <m:mo>−</m:mo> </m:msup> <m:mo stretchy="false">)</m:mo> <m:mi>B</m:mi> <m:mo stretchy="false">(</m:mo> <m:mi>ϕ</m:mi> <m:mo stretchy="false">→</m:mo> <m:mi>η</m:mi> <m:mi>γ</m:mi> <m:mo stretchy="false">)</m:mo> </m:math> has been obtained. </jats:p>