Speaker
Description
Detection schemes for the QCD axions and other axion-like particles (including axionic Dark Matter) in light-shining-through-a-wall (LSW) experiments are based on the conversion of these particles into photons in a magnetic field. An alternative scheme may involve the detection via a resonant atomic or molecular transition induced by resonant axion absorption. The signal obtained in this process is second order in the axion-electron interaction constant but may become first order if we allow interference between the axion-induced transition amplitude and the transition amplitude induced by the electromagnetic radiation that produces the axions.
The interaction of Standard Model's particles with the axionic Dark Matter field may generate oscillating nuclear electric dipole moments (EDMs), oscillating nuclear Schiff moments and oscillating nuclear magnetic quadrupole moments (MQMs) with a frequency corresponding to the axion's Compton frequency. Within an atom or a molecule an oscillating EDM, Schiff moment or MQM can drive transitions between atomic or molecular states. The excitation events can be detected, for example, via subsequent fluorescence or photo-ionization. If the nucleus has octupole deformation or quadrupole deformation or both then the transition rate due to Schiff moment and MQM can be up to $10^{-18}$ transition per molecule per year. In addition to causing transitions, an oscillating nuclear EDM can also induced an atomic or molecular EDM, which can be directly measured in an external electric field. This results overcomes the famous Schiff theorem which states that a static nuclear EDM is completely screened from any static external electric field.
