Search for the radiative capture reaction d+d → 4He+γ from the ddμ muonic molecule state

A search for the muon-catalyzed fusion (MCF) reaction d+d → 4He+γ in the ddμ muonic molecule was performed using the experimental MCF installation TRITON and NaI(Tl) detectors for γ quanta. A high-pressure target filled with deuterium was exposed to the negative muon beam of the JINR phasotron to detect γ quanta with an energy of 23.8 MeV. The first experimental estimation for the yield of radiative deuteron capture from the ddμ state J=1 was obtained at a level of ηγ≤2×10−5 per one fusion.