Comparing Instrument Spectral Sensitivity of Dissimilar Electromagnetic Haloscopes to Axion Dark Matter and High Frequency Gravitational Waves

Michael E. Tobar, Catriona A. Thomson, William M. Campbell, Aaron Quiskamp, Jeremy F. Bourhill, Benjamin T. McAllister, Eugene N. Ivanov, Maxim Goryachev

Submitted on 7 September 2022


It is known that axion haloscopes that operate to search for dark matter axions via the 2-photon anomaly are also sensitive to gravitational waves (GWs) through the inverse Gertsenshtein effect. Recently this way of searching for high frequency GWs has gained momentum as it has been shown that the strain sensitivity of such detectors, h_g, are of the same order of sensitivity as the axion-photon theta angle, \theta_a, which is related to the axion 2-photon coupling, g_{a\gamma\gamma}, by, \theta_a = g_{a\gamma\gamma}a, where, a, is the axion scalar field. This means after calculating the sensitivity of a haloscope to an axion signal, we also have calculated the order of magnitude sensitivity to a GW signal of the same spectral and temporal form. However, it is unlikely that a GW and an axion signal will be of the same form since physically the way the signals are generated are completely different. For GW detection, the spectral strain sensitivity in units strain per square root Hz, and is the natural way to compare the sensitivity of GW detectors due to its independence on the GW signal. Likewise, one can define a spectral axion-photon theta angle sensitivity in units of theta angle per square root Hz for axion detectors, which is independent of the axion signal. In this work we introduce a systematic way to calculate the spectral sensitivity of an axion haloscope so instrument comparison may be achieved independent of signal assumptions and only depends on the axion to signal transduction sensitivity and noise in the instrument. Thus, the calculation of the spectral sensitivity not only allows the comparison of dissimilar axion detectors independent of signal, but also allows comparison of the GW sensitivity in terms of spectral strain sensitivity, allowing comparisons to standard GW detectors based on optical interferometers and resonant-mass technology.


Subjects: Physics - Instrumentation and Detectors; Astrophysics - Instrumentation and Methods for Astrophysics; General Relativity and Quantum Cosmology; High Energy Physics - Experiment