Xi (-) atomic X-ray spectroscopy using a counter-emulsion hybrid method

Xi(-) atomic X-ray spectroscopy is one of the most useful methods for investigation of the Xi-nucleus strong interaction. Since the X-ray energy is shifted and/or broadened due to the Xi-nucleus strong interaction compared to those calculated from electromagnetic interaction alone, the measurement of the energy shift, Delta E, and the width, Gamma, give us information on the Xi-nucleus potential. A serious problem in the measurement is the significant background derived from in-flight Xi(-) decay. A novel method of identifying stopped Xi(-) events using the nuclear emulsion was developed to realize the first Xi(-) atomic X-ray spectroscopy experiment as the J-PARC E07 experiment, which also aimed at searching for ?? and Xi(-) hypernuclei in the emulsion. The X-rays emitted from Xi(-) Br and Xi(-) Ag atoms were measured using germanium detectors. No clear peaks were observed in the obtained spectra. However, we succeeded in reducing the background to 1/170 by this method employing coincidence measurements using nuclear emulsion and X-ray detectors.