Cryogenic Cavities for a Dark Matter Search

Joint CFP Project: This joint effort of the Gabrielse group (members pictured), the Geraci group, the Kovachy group, and the Odom group illustrates the opportunities available within Northwestern University's unique Center for Fundamental Physics (CFP).

Andra Ionescu	Xing Fan	Tharon Morrison	Gerald Gabrielse

Motivation: Unidentified dark matter (not observed with visible light) needed to explain the observed motion of galaxies is 5 times more abundant than the observed matter. Ultralight scalar fields, especially well-motivated candidates because they naturally arise in string theory [1], lead to temporal oscillations fundamental constants like the fine structure constant or the electron mass at the characteristic mass of the field [2].

Enabling Methods

1. A laser probes the resonant frequencies of two cavities, to detect oscillations in the length of a rigid laser cavity in the audio frequency range (0.1-10 kHz) caused by dark matter. Its resonance frequency will be compared to that of a suspended-mirror cavity that cannot change this rapidly [3].
2. Cryogenic cavities will be used to suppress leading thermal effects, like the thermal fluctuations of mirror surfaces, for an extremely sensitive search for the dark matter.

Current status: Apparatus is being designed and acquired.

Funding: We are grateful to the Templeton Foundation for funding the design and preparation of the new cryogenic apparatus to search for dark matter.

References

[1] S. Dimopoulos and G. Giudice, Physics Letters B 379, 105 (1996).
[2] T. Damour and J. F. Donoghue, Phys. Rev. D 82, 084033 (2010).
[3] A. A. Geraci, C. Bradley, D. Gao, J. Weinstein, and A. Derevianko, Phys. Rev. Lett. 123, 031304 (2019).