On Earth, it is mainly in particle accelerators that the quest for new particles is played out. It had a brilliant result in July 2012 with the discovery of the Higgs boson. Since then, however, physicists have been less inclined to party: their experiments to uncover other, more exotic particles like Weakly Interacting Massive Particles, or WIMPs have so far failed, despite a few alerts. It is a great pity because the latter were ideal candidates for understanding what dark matter is made up of, this elusive matter essential to explain the behavior of galaxies. Suddenly, specialists, never disillusioned, turn to other hypotheses and other candidate particles. The axion is one of them. And if its name reminds you of a brand of detergent, that’s normal! It is indeed for this reason that it was named thus: it was supposed to “clean up” a major problem of a new theory, quantum chromodynamics. But now she too is missing even if a signal recorded in the experiment tank Xenon1T leaves some doubt. Most recently, it is towards the stars that the hopes of theorists have been directed since they think they have detected, finally, indirect traces of this particle.
The axion, a very useful particle
“The axion is a fundamental particle like the electron, the photon or the neutrinos. However, unlike these particles, the axion is hypothetical. This means that we do not yet know if it exists in nature. This is what we are trying to find out. There are, however, theoretical reasons to suspect that such a particle might exist. Axions can solve long-standing anomalies related to the behavior of neutrons in the presence of electric fields“, explains to Science and the Future Benjamin Safdi, theoretical physicist at Lawrence-Berkeley National Laboratory (Berkeley Lab) in California. The proof of the existence of the axion would also help to solve the string theory and this particle constitutes a candidate of choice to explain the nature of the dark matter. “If axions exist, they would be bosons, like the Higgs boson. Unlike the Higgs boson, however, they are said to be ultralight, like neutrinos. Axions would also interact very weakly with ordinary matter, as neutrinos do“, he adds.