Detection of Scalar Wave Dark Matter with a Levitated Superconductor

Abstract

The nature of dark matter is one of the most elusive problems in modern physics. With varying candidates and a vast range of possible particle masses, there is still no direct evidence of dark matter through an experimental observation. In this thesis, the possibility of detecting dark matter in a laboratory setup is theoretically investigated. The candidate in question will be the scalar case of the wave-like dark matter, a particle dark matter that belongs in the ultralight mass spectrum. The proposal is that this type of dark matter can be described by a classical wave instead of a quantum field and will interact with neutrons in matter through a simple, linear, non-derivative term in the Lagrangian. This interaction would result in an sinusoidal force that can be detected in a proposed magnetically levitated superconductor experiment. The experimental setup is parametrized as a coupled harmonic oscillator system, where a vibrational shield is installed to minimize vibrational noise. Through stochastic modeling of vibrational noise and numerical methods such as Monte Carlo simulations, the motion of the target superconductor is studied. The end result of this analysis is the projected sensitivity of the proposed experiment, expressed as exclusion limits on the coupling strength as a function of dark matter mass. We conclude that in a two-stage model, with experimental parameters corresponding to a possible levitation experiment in Chalmers, the vibrational noise is identified as the dominant noise source, exceeding both thermal, imprecision and back-action noise due to the measurement device (SQUID), significantly limiting the sensitivity. For comparison, the minimum coupling per unit mass in an ideal case with linearly scaled down vibrational noise is also presented, along with an analytical sensitivity projection.