Search for dark-matter axions beyond the quantum limit: The cosmological axion Sarov haloscope proposal

Firmly established in astrophysical observations, dark matter evades direct detection in experiments. Axions and axionlike particles are among the leading dark-matter candidates, and numerous attempts to detect them in laboratories have been performed. Here, we propose to advance these efforts substantially, extending the sensitivity for dark-matter axions in the mass range <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mo stretchy="false">(</a:mo><a:mn>38</a:mn><a:mi>–</a:mi><a:mn>54</a:mn><a:mo stretchy="false">)</a:mo><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi mathvariant="normal">μ</a:mi><a:mi>eV</a:mi></a:mrow></a:math> down to the axion-photon couplings <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:msub><f:mi>g</f:mi><f:mrow><f:mi>a</f:mi><f:mi>γ</f:mi><f:mi>γ</f:mi></f:mrow></f:msub><f:mo>≲</f:mo><f:mrow><f:mo stretchy="false">(</f:mo><f:msup><f:mn>10</f:mn><f:mrow><f:mo>−</f:mo><f:mn>14</f:mn></f:mrow></f:msup><f:mo>−</f:mo><f:msup><f:mn>10</f:mn><f:mrow><f:mo>−</f:mo><f:mn>15</f:mn></f:mrow></f:msup><f:mo stretchy="false">)</f:mo></f:mrow><f:mtext> </f:mtext><f:mtext> </f:mtext><f:msup><f:mi>GeV</f:mi><f:mrow><f:mo>−</f:mo><f:mn>1</f:mn></f:mrow></f:msup></f:math>, motivated by generic models of quantum chromodynamics axion. Single-photon detectors operating at ultralow temperatures are key elements of the experiment. The projected sensitivity will be reached in one year of data taking with magnetic field of (1–10) T, making Cosmological Axion Sarov Haloscope (CASH) the most sensitive haloscope in this mass range.