Matter radius of Kr 78 from proton elastic scattering at 153 MeV

Small-angle differential cross sections of proton elastic scattering off Kr78 with a collision energy of 152.7 MeV/u were measured at the experimental Cooler Storage Ring of the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR). Low energy recoil protons from the elastic scattering were counted by a silicon-strip detector to determine relative differential cross sections. A model-dependent root-mean-square matter radius of 4.16(12) fm for the Kr78 nucleus was deduced by employing the Glauber model. Compared to the proton radius of 4.13 fm for Kr78, our center value of matter radius is slightly larger. This finding in Kr78 is opposite to the known results of Kr76,80, where the matter radii are smaller than the corresponding proton radii. However, considering the relatively large radius error of Kr78, the difference is not statistically significant, and further experiments are necessary.