Precision spectroscopy of kaonic helium-3 3d → 2p X-rays

The E17 experiment measures the kaonic helium-3 X-rays using the large area silicon drift detectors (SDDs) in the new kaon beam line at the J-PARC facility in Japan. The X-ray measurements of kaonic atoms give important information on the low-energy anti KN interaction. In particular, the determination of the shift and width of the kaonic 3He and 4He 2p states is a matter of the highest priority on the hadron physics. For example, the Akaishi-Yamazaki theory predicts the existence of the deeply bound kaonic nuclear states. Many experiments to observe such states have been progressed, but the measurements of the shift and width of the kaonic helium 2p states are also important values. The theory predicts a possible large shift of up to 10 eV. The first convinced result was obtained in the E570 experiment at KEK, which shows a shift of +2±2±2 eV. Together with the data on kaonic 4He atoms, the data on kaonic 3He atoms is a very important physical quantity to check the theoretical model. In this talk, the status of the E17 experiment, in particular the working progress of the SDD system is reported.