Realistic Time Budget for Axion Haloscope Experiments

The QCD Axion is one of the leading candidates to explain what constitutes dark matter [1-4]. Searches for these axions involve a resonant microwave cavity, called a haloscope, placed in a magnetic field, where the axion scatters with the magnetic field and deposits a photon in the cavity only if the resonant frequency of the cavity matches that of the axion [5]. However, given the axion frequency is not known a priori, haloscope searches must scan across many orders of magnitude. Assuming the quality factor of such a cavity is the optimal 10^6 or higher (which matches the predicted axion linewidth), we argue that to cover the full range of frequencies in a realistic amount of time, these searches only have 10 seconds worth of integration time at each frequency. Given the specifics of any one experiment, this will constrain what kind of signal rates and background rates are required. Specific experimental examples will be discussed.

[1] Peccei, R. D. & Quinn, H. R. Constraints imposed

by CP conservation in the presence of pseudoparti-

cles. Phys. Rev. D (1977).

[2] Peccei, R. D. & Quinn, H. R. CP conservation in the

presence of pseudoparticles. Phys. Rev. Lett. (1977).

[3] F.Wilczek,Phys.Rev.Lett.40,279(1978).

[4] S.Weinberg,Phys.Rev.Lett.40,223(1978).

[5] Sikivie, P. Experimental tests of the ”invisible” ax-

ion. Phys. Rev. Lett. 51, 1415–1417 (1983).