Ultra-sensitive Searches for Dark-Matter Axions

The axion is an interesting hypothetical particle. It arose from a solution to the "Strong CP Problem" in the Standard Model of particle physics, and it happens to be an ideal dark matter candidate. Hence, axions would be a very compelling addition to the particle zoo. However, The axion is exceedingly hard to detect. A dark-matter axion does indeed decay, but with a lifetime of perhaps 1050 years. This colloquium will describe this interesting particle and an experiment that aims to detect its incredibly feeble decay by an apparatus consisting of a strong static magnetic field threading a high Q microwave resonator. Nearby relic axions inside the resonator convert into a sub-yoctoWatt microwave signal, which in turn is amplified and detected by the world's lowest-noise quantum-noise-limited SQUID amplifier-receiver. This experiment has improved over the years and now has the sensitivity to detect such axions or reject the dark-matter axion hypothesis at high confidence.

Room 1