Muon nuclear capture reaction on ^28,29,30Si

The muon nuclear capture is a reaction of a negative muon and a proton in nuclei via weak interaction. The reaction produces an excited nucleus, from which several particles are emitted. The experimental data concerning the muon nuclear capture, especially about the distributions of the excited states, such as the branching ratio (BR) of residual nuclei and the energy distributions of emitted particles, are limited for the moment. And there is also no established model that can describe the muon nuclear capture and its following particle emissions. The production BR of each daughter nucleus resulting from the muon capture of silicon was measured with some methods, but these methods contain several assumptions and show some discrepancies in the number of charged particle emissions. Therefore, we measured the absolute production BR of the muon capture to obtain accurate data and evaluate the excitation states of Si isotopes after the muon capture.

The experiments were performed at the pulsed muon facilities, MLF at J-PARC and RAL-ISIS. The negative muon beam irradiated enriched ^28,29,30Si targets. The numbers of reaction products were measured with the activation method and the absolute BRs were deduced. The BR of ²⁶Al was measured with the Accelerator Mass Spectrometry (AMS) method at MALT, the University of Tokyo.

The absolute BRs of unstable Na, Mg, and Al isotopes were observed in these experiments. The result of the experiments will be reported in this presentation and compared with theoretical calculations.