Magnetized media as detectors for galactic axions.

Braggio C., Carugno G., Gallo C.S., Lombardi A., Ortolan A., Pengo R., Ruoso G.
  Giovedì 29/09   09:00 - 13:00   Edificio Psicologia 2 - Aula 2E   III - Astrofisica
The axion is a particle with remarkable properties, which followed the introduction by Roberto Peccei and Helen Quinn of a neutralizing field to solve the strong CP problem. Theorists have developed models that predict long-lived, very light axions, with mass ranging from $\mu$eV to meV, and as their mass is proportional to the interaction with ordinary barionic matter, they are expected to be effectively invisible. However, so as the assumed value of the axion mass decreases, its cosmological abundance is driven up, making it an excellent non-thermal dark matter candidate. An axion fluid would pervade the universe as the CMB does and an observer on Earth, in motion through the galactic halo, would then perceive an "axion wind". We will report about a proposal to detect such galactic axions in the 100 $\mu$eV mass range through their interaction with the spin of fermions. The experimental setup is based on a magnetized sample with Larmor resonance frequency tuned to the axion mass by application of a static magnetic field. The interaction with the "axion wind", that is represented by an effective microwave field, drives the total magnetization of the sample and originates oscillations in the magnetization that can be detected by a suitable detector.