The Ξ^- atom X-ray spectroscopy at J-PARC

Studying hyperon-nucleon interactions is important for more general understanding of nuclear force. We can extend the NN interaction with the isospin SU(2) symmetry to the baryon-baryon interactions under the flavor SU(3) symmetry. However, experimental data for the S = -2 sector, particularly on the ΞN interaction, are very limited. One way to obtain such information is a measurement of X rays from Ξ^- atoms by obtaining energy shifts of the atomic levels from those precisely calculated based purely on electromagnetic interaction. From the shifts, information on the ΞN potential can be extracted. In 2016 and 2017, we measured X rays from Ξ^- atoms with a Germanium (Ge) detector array, Hyperball-X, at J-PARC using a hybrid emulsion method for the first time. The current analysis status of the Hyperball-X data is reported. (author)