Speaker
Description
The $\eta^{\prime}$ meson has an extraordinary large mass among the light pseudo-scalar meson nonet.
The large mass is considered to originate from the non-trivial vacuum structure associated with chiral symmetry breaking and the axial U(1) anomaly in the QCD.
In a nuclear medium, where the chiral symmetry is partially restored, the mass reduction of the $\eta^{\prime}$ meson is predicted by 37--150~MeV/$c^2$ depending on theoretical models.
Since such a mass reduction leads to an attractive potential of $\eta^{\prime}$ meson to the nucleus, bound state of $\eta^{\prime}$ mesons and nuclei (=$\eta^{\prime}$-mesic nuclei) is expected to exist.
We performed an experimental search for $\eta^{\prime}$-mesic nuclei by missing-mass spectroscopy in $^{12}\mathrm{C}(p,dp)$ reaction using the WASA detector at the FRS in 2022 February, which was a coincidence measurement of forward deuterons and protons from decay of $\eta^{\prime}$-mesic nuclei ($\eta^{\prime} NN \rightarrow NN$).
We employed 2.5~GeV proton beams with an intensity of $\sim 3\times10^{8}/s$ and placed a $^{12}\mathrm{C}$ target at FRS-F2 focal plane.
The decay products of $\eta^{\prime}$-mesic nuclei were measured with the WASA detector installed at the FRS-F2 focal plane and the forward deuteron momenta were analyzed by the FRS.
In this presentation, we will present details of the experiment and the current status of the analysis.
