Study of Y* in Nuclei through C(K−, π+)X Spectrum at 1.8 GeV/c in the J-PARC E05 Experiment

We measured the (K^−, π^+) reaction spectra at 1.8 GeV/c for the graphite and the polyethylene targets in the J-PARC E05 pilot experiment. By comparing the spectra for these two targets, it was found that Σ^*−(1385) in the ^11B nucleus is quite broadened. Furthermore, we also compared broadness of Σ^*−(1385) with K^*(892) obtained in the (K^−, p) spectrum. Σ^*−(1385) seems to be much more broadened in nuclei than K^*(892). We gave a possible interpretation, which is related to compositeness of decuplet baryons, for this situation.