Follow-up search for a tentative dark photon signal near <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mn>19.5</mml:mn> <mml:mtext> </mml:mtext> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">μ</mml

A recent independent dark photon (DP) focused reanalysis of existing data from the TASEH axion haloscope experiment reported a tentative DP dark matter signal with local significance <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mo>∼</a:mo> <a:mn>4.7</a:mn> <a:mi>σ</a:mi> </a:math> at a frequency <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mrow> <c:mi>f</c:mi> <c:mo>≈</c:mo> <c:mn>4.71</c:mn> <c:mtext> </c:mtext> <c:mtext> </c:mtext> <c:mrow> <c:mi>GHz</c:mi> </c:mrow> </c:mrow> </c:math> , corresponding to <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mrow> <e:msub> <e:mrow> <e:mi>m</e:mi> </e:mrow> <e:mrow> <e:mi>X</e:mi> </e:mrow> </e:msub> <e:mo>≈</e:mo> <e:mn>19.5</e:mn> <e:mtext> </e:mtext> <e:mtext> </e:mtext> <e:mi mathvariant="normal">μ</e:mi> <e:mi>eV</e:mi> </e:mrow> </e:math> and kinetic mixing <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"> <h:mrow> <h:mi>ϵ</h:mi> <h:mo>∼</h:mo> <h:mn>6.5</h:mn> <h:mo>×</h:mo> <h:msup> <h:mrow> <h:mn>10</h:mn> </h:mrow> <h:mrow> <h:mo>−</h:mo> <h:mn>15</h:mn> </h:mrow> </h:msup> </h:mrow> </h:math> . Motivated by this report, we performed a dedicated, narrowband follow-up experiment to confirm or refute the signal with a cryogenic microwave cavity operated a magnetic field, leveraging the ORGAN-Q dilution refrigeration and receiver chain. Scanning a window centered on the reported frequency over a live time of <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"> <j:msub> <j:mi>T</j:mi> <j:mi>int</j:mi> </j:msub> <j:mo>∼</j:mo> <j:mn>13</j:mn> <j:mtext> </j:mtext> <j:mtext> </j:mtext> <j:mi>days</j:mi> </j:math> , we find no excess consistent with a dark photon signal as reported, and set a 95% CL of <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"> <l:mrow> <l:mi>ϵ</l:mi> <l:mo>≤</l:mo> <l:mn>5.04</l:mn> <l:mo>×</l:mo> <l:msup> <l:mrow> <l:mn>10</l:mn> </l:mrow> <l:mrow> <l:mo>−</l:mo> <l:mn>15</l:mn> </l:mrow> </l:msup> </l:mrow> </l:math> in a narrow mass range around <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"> <n:mo>∼</n:mo> <n:mn>19.5</n:mn> <n:mtext> </n:mtext> <n:mtext> </n:mtext> <n:mi mathvariant="normal">μ</n:mi> <n:mi>eV</n:mi> </n:math> , excluding a signal of the strength and frequency reported to 99.92% confidence. We discuss the experiment and present the exclusion limits.