The equation of state (EOS) of nuclear matter is important not only for understanding the properties and dynamics of nuclei but also for explaining the astrophysical phenomena, such as neutron stars merger and supernova explosions. Research on the EOS from experimental nuclear physics attempts to determine the behavior near saturation density and symmetric nuclear matter from nuclear reactions. Recent studies have suggested that high-precision and high-accuracy measurements of the isospin-dependent term of incompressibility, , are crucial.
can be directly determined from the isoscalar giant monopole resonance (ISGMR). In previous studies, MeV was obtained from ISGMR measurements of Sn isotopes based on the liquid drop model. However, the uncertainty is large due to these measurements being limited to stable nuclei and the assumptions about surface effect. Additionally, phenomena beyond the liquid drop model, such as deformation and softness, have been observed. Therefore, to elucidate the fundamental properties of nuclear matter, including incompressibility and the nuclear matter EOS, it is necessary to survey the ISGMR over a wide range of the nuclear chart and conduct a more in-depth discussion through the ISGMR strength function.
To achieve purpose, we developed an active target (CAT-M), a measurement device where the target itself functions as a detector. As the first step towards the systematic measurement of ISGMR, we performed ISGMR measurements of Kr in HIMAC of NIRS-QST. As a result, we determined the centroid energy of the ISGMR to be 17 1 MeV. In this presentation, we will report the details of this experiment and discuss future plans for ISGMR measurements in unstable nuclei.
