Status and future plan of the spectroscopy of pionic atoms

The spectroscopy of deeply bound pionic atoms provides a way to understand the restoration of chiral symmetry breaking at unite density. We have been performing a series of experiments of missing-mass spectroscopy of the (d,He-3) reaction at HIRE to investigate pionic atoms of several Sn isotopes. As a first step, we conducted a pilot experiment to measure deeply bound pionic states of Sn-121 and successfully observed the deeply bound pionic states. In addition to the experiment at RIBF, we are planning the spectroscopy of deeply bound pionic atoms in inverse kinematics and conducted a feasible study by simulations. We showed that by using a deuterium gaseous active target TPC and silicon detectors, the Q-value resolution is about 500 keV (FWHM) and the yield of the pionic Is state is 20 counts/day, indicating the experiment is feasible.