Feasibility study to search for the rare γ-decay mode in 12C

Excited states in 12C nuclei play a very important role in the nucleosynthesis in the universe. 12C nuclei are synthesized by the triple α reaction. Normally this process proceeds via the 0+2 state (Hoyle state) at Ex = 7.65 MeV in 12C, however, at high temperature T > 109 the highly excited 3α resonant states such as the 3−1 state at Ex = 9.64 MeV and the 2+2 state at Ex = 9.84 MeV play a part of the triple α reaction. Unfortunately, the γ-decay probability of the 3p state has not been determined, therefore we planned to determine the 7- decay probability using the inverse kinematic reaction 1H(12C, 12Cp) without measuring γ-rays. The test experiment was carried out at the cyclotron facility in RCNP. The results of the test experiment are reported in the present paper.