Special Seminar: Karl van Bibber (UC Berkeley): "ALPHA – The search for the post-inflation axion", Jospeh Henry Room

Jun 26, 2024, 11:00 am12:00 pm
Joseph Henry Room


Event Description

The axion, a hypothetical ultralight pseudoscalar resulting from the most compelling solution to the Strong-CP problem, also represents an increasingly favored candidate to constitute the dark matter of the Universe.  The most sensitive search modality to date is based on the resonant conversion of axions to photons in a high-Q cavity in a strong magnetic field, i.e. a narrow-band tuning experiment.  Problematically the mass of the axion is unknown and only bounded within ten orders of magnitude, but in one cosmological scenario where Peccei-Quinn symmetry breaking occurs after inflation, the axion mass is in principle exactly calculable.  While the best supercomputer calculations have not converged on a unique prediction so far, what is clear is that the mass, or equivalently frequency, is at a scale beyond where conventional microwave cavities are feasible for such a search.  A recent concept for metamaterial-based resonators whose plasma frequency could be engineered and tuned to the range of interest has spurred a vigorous global R&D effort, which ultimately resulted in a new experiment now under construction, ALPHA.