The paper presents the latest results in the search for solar axions being conducted in the CAST experiment since 2003. Axions are hypothetical particles, originally proposed as a solution to the significant CP problem in quantum chromodynamics, and are also candidates for cosmological dark matter. The search for them has lasted about thirty years and a signal of their existence has yet to be found. The CAST experiment searches for axions that emerge from the center of the sun in two-photon interaction and represent the upper limits of axion-photon coupling for the large range of axion masses, and is the most sensitive experiment of its kind in the world. According to the measurements described in the paper, the most exact limits thus far have been established for axion-photon coupling strength for a large area of axion mass. For the first time, the part of the parameter area is being explored that predicts theoretical axion models, providing a significant contribution to the further search for axions.

The aforementioned RBI scientists are actively involved in the planning and execution of the experiments and the publication of papers. So far, they have been chosen by foreign collaborators for three scientific articles published in prestigious scientific journals, including Physical Review Letters, IF=7.621 (B. Lakić: the aforementioned paper), and the Journal of Cosmology and Astroparticle Physics, IF=6.497 (K. Jakovčić: JCAP12(2009)00kk2 and M. Krčmar: JCAP04(2007)010).