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Calculating the Mass of the Axion

Researchers at JSC – Zoltan Fodor, Taichi Kawanai, Simon Mages, and Kalman Szabo – together with colleagues from Wuppertal, Budapest, and Hamburg calculated the mass of the axion, with the result recently published in Nature (see DOI:10.1038/nature20115).

The axion is a hypothetical elementary particle, which is believed to be the key to solving two major puzzles in fundamental physics. The first is the pressing question of why the strong interaction is surprisingly symmetric under the transformation which exchanges left with right. Axions can solve this problem by cancelling the possible symmetry violating parts of the strong interaction. The second long-standing puzzle is that of dark matter: according to current astrophysical and cosmological observations only 15 % of our Universe is visible and the rest is dark, which means that they have practically no interaction with known particles such as photons. Axions are viewed as being a natural candidate for the particles out of which dark matter is made. The theory behind this predicts a tiny but non-zero coupling to photons, which can be used to detect them in laboratory experiments. For several years now, many experiments have attempted to find such particles – but so far without success. The difficulty in these experimental searches is that the mass of the axion is not known beforehand, a parameter on which the design of the experimental apparatus crucially depends.

The researchers have succeeded in deriving a mass range for the axion based on the assumption that these particles constitute dark matter. For this calculation, the details of the strong interaction had to be accurately modelled, for which the supercomputing resources of JUQUEEN were inevitably required. The result is an important contribution to the experimental search for these particles. The Nature Editorial Board has chosen to highlight the result in its News&Views section (see DOI:10.1038/539040a).
(Contact: Prof. Kalman Szabo,

JSC News No. 246, December 2016