Speaker
Description
"$\eta^{\prime}(958)$ meson has an exceptionally large mass compared with the other light pseudo-scalar meson nonets. The origin of the large mass is considered to have a close relation to the chiral symmetry breaking and the axial U(1) anomaly in the QCD. In a nuclear matter, where the chiral symmetry is partially restored, a mass reduction of an $\eta^{\prime}$ meson is predicted by several theoretical models. Since such a mass reduction leads to an attractive potential for the $\eta^{\prime}$ meson in a nucleus, the existence of bound states between $\eta^{\prime}$ mesons and nuclei (=$\eta^{\prime}$-mesic nuclei) has been suggested.
To search for $\eta^{\prime}$-mesic nuclei, we conducted missing-mass spectroscopy of $^{12}\mathrm{C}(p,d)$ reaction in a coincidence detection of protons from the two nucleon absorption decay of $\eta^{\prime}$-mesic nuclei using a large solid angle detector WASA at the fragment separator (FRS) in GSI in 2022 February. We made use of 2.5 GeV proton beams with an intensity of $3.0\times 10^8/s$ and a $^{12}\mathrm{C}$ target with a thickness of 4 g/cm$^{2}$. The momenta of the forward emitted deuterons were analyzed by the FRS and the protons with momenta of $\sim$1 GeV/$c$ from the decay of $\eta^{\prime}$-mesic nuclei with the WASA detector simultaneously.
This presentation will provide the experimental details and the current situation of the data analysis."
