New experiment on search for the resonance absorption of solar axion emitted in the M1 transition of 83Kr nuclei

Axions with an energy of 9.4 keV emitted in the M 1 transition of 83 Kr nuclei in the Sun have been sought in the resonance absorption reaction A + 83 Kr → 83 Kr* → 83 Kr + γ, e (9.4 keV). A proportional gas chamber filled with krypton and placed in a low-background setup at the underground laboratory of the Baksan neutrino observatory was used to detect γ-ray photons and electrons appearing after the decay of a nuclear level. As a result, a new constraint has been determined on the isoscalar and isovector coupling constants of the axion with nucleons: | g AN 3 – g AN 0 | ≤ 1.29 × 10 –6 . This constraint results in the following new bound on the mass of the axion in the hadronic axion model: m A ≤ 100 eV (95% C.L.).