In recent months and days we have started hearing more and more about the axion particle. I am interested in the axion proposal because it is the only theorized particle that turns into a photon in the presence of a strong magnetic field. Other particles, if they have electrical charge, are influenced by the magnetic field and they may even emit photons but they don’t turn into photons because of the magnetic field. You may have seen Feynman diagrams showing photons emerging from particle interactions. Those interactions are typically hard collisions between elementary particles or interactions depicting particle decays. For example, when electron and positron collide they annihilate each other and 2 photons emerge. Axion turning into a photon in the presence of a strong magnetic field is a different type of interaction. This is an important point.
Axion is supposed to be a spin=0 particle. So far we have observed only one particle with spin=0, the Higgs particle. Axion would be the other spin=0 particle in nature. This would be very important to know.
Axion does not interact with matter very much and axion is supposed to have a very small mass. In these respects axions would be similar to neutrinos except for an important difference. Neutrinos are spin=1/2 particles.
I found the best introduction to axion in a document provided by the Caltech Astronomy department
This document is still very technical but you may get the gist of the axion proposal.
It is also interesting to note that the billionaire mathematician Jim Simons is funding projects searching for axions.