In-beam γ spectroscopy of ⁵⁵Ca and ⁵⁵K via nucleon knockout reactions

The shell model is very successful in describing the properties of stable nuclei. However, modifications of the nuclear shell structure have been observed especially for the nuclei far from stability. For very exotic Ca isotopes, new magic numbers at N = 32, 34 have been inferred from gamma-ray spectroscopy and mass measurements. However, more direct indications for shell closures can be obtained from the single-particle structure of neighboring nuclei.

In this study we have investigated the proton and neutron single particle structure of ⁵⁶Ca using knockout reaction combined with in-beam gamma-ray spectroscopy. The experiment was performed at RI Beam Factory, Japan. A primary ⁷⁰Zn beam with 345 MeV/u impinged on 10 mm-thick ⁹Be production target. Secondary beams including ⁵⁶Ca were separated and identified by BigRIPS and impinged on the liquid hydrogen target MINOS. The detector array DALI2 was placed around MINOS to measure the gamma-rays emitted from the reaction products. Fragments were identified by the large-acceptance multi-particle spectrometer SAMURAI.

In this talk we will present the preliminary results and comparison to theoretical calculations.

In-beam γ spectroscopy of ⁵⁵Ca and ⁵⁵K via nucleon knockout reactions.