The nature of the ubiquitous dark matter of the Universe is one of the most important questions in all of science today. A leading candidate is a hypothetical ultralight particle, the axion, which is well motivated as a solution to the 'Strong-CP' problem, i.e. why the strong (nuclear) force does not violate the product symmetry of parity (spatial reflection) and charge conjugation (transformation of particles into their antiparticles), as is manifested in the absence of a neutron electric dipole moment.
For many years now, groups around the world have searched for dark matter axions by looking for their resonant conversion to photons in a tunable microwave cavity permeated by a strong magnetic field. Under the best of circumstances, the expected signal is extraordinarily week, a trillionth of a trillionth of a watt, and thus the axion search has been both a driver and a beneficiary of advances in quantum detection. Recent theoretical work, however, suggest that the axion's mass (and thus frequency of the experiment) may be tightly constrained, which would dramatically improve prospects of its discovery. The predicted mass, or frequency, however is higher than can be feasibly scanned with microwave cavities, but a new paradigm for the resonator, a wire-medium metamaterial appears promising to carry out this search.
An international team of researchers has come together to propose such an experiment, ALPHA, that would capitalize on the availability of a very high-field superconducting magnet sited at Yale University. The team represents all the requisite know-how in the design, construction and operation of axion haloscopes, and in the science and technology of metamaterials. The team proposes to construct and begin operation of ALPHA within five years, and offers an unprecedented opportunity for discovery of the dark matter.
