Experimental search for the radiative capture reaction d + d → 4 He + γ from the dd μ muonic molecule state J = 1

A search for the muon-catalyzed fusion reaction d + d → 4 He + γ in the dd μ muonic molecule was performed using the experimental installation TRITON with BGO 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 the energy 23.8 MeV. An experimental estimation for the yield of radiative deuteron capture from the dd μ state J = 1 was obtained at the level of η γ ≤ 8 × 10 −7 per fusion.