Speaker
Description
The significantly large mass of the $\eta(958)$ ($\eta'$) meson within the other light pseudoscalar mesons is understood to be generated by the $\rm U_{A}(1)$ anomaly and the chiral symmetry breaking. In the nuclear medium, the $\eta'$ mass is considered to be reduced due to a partial restoration of chiral symmetry [1]. The reduction of the $\eta'$ mass leads to an attractive $\eta'$-nucleus interaction and to a possible existence of $\eta'$-nucleus bound states, namely $\eta'$-mesic nuclei [2]. The $\eta'$-mesic nuclei are believed to provide new insights of the properties of $\eta'$ meson and the aspects of strong interaction at finite nuclear density.
The first experiment to search for the $\eta'$-mesic nuclei by the missing mass spectroscopy in the $^{12}{\rm C}(p, d)$ reaction was performed at GSI [3, 4, 5] and the excitation energy spectrum of $^{11}{\rm C}$ around $\eta'$-meson threshold was obtained. Since no peak structure indicating the $\eta'$ bound states was found, the upper limits of the formation cross section and the constraints for the $\eta'$-nucleus potential parameters were determined [5, 6].
In the analyses in Refs. [5, 6], the $^{11} {\rm C}$ core nucleus in the $\eta'$-mesic nuclei was implicitly assumed to have the standard nuclear density distribution as usual stable nuclei. However, the latest theoretical work reported in Ref. [7] indicated the possible change of the density distribution of $^{11}{\rm C}$ due to the interaction with $\eta'$. Thus in this report we investigate theoretically the nuclear deformation (compression) effects to the structures and the formation spectra of $\eta'$-$^{11}{\rm C}$ bound states to provide the realistic basis to deduce the physical information from the experimental spectra.
Reference
[1] D. Jido, H. Nagahiro and S. Hirenzaki, Phys. Rev. C85 (2012) 032201.
[2] H. Nagahiro and S. Hirenzaki, Phys. Rev. Lett. 94 (2005) 232503.
[3] K. Itahashi et al., Prog. Theor. Phys. 128 (2012) 601-613.
[4] H. Nagahiro et al., Phys. Rev. C87(2013) no.4, 045201.
[5] Y. K. Tanaka et al., Phys. Rev. Lett. 117 (2016) no.20, 202501.
[6] Y. K. Tanaka et al., Phys. Rev. C97 (2018) no.1, 015202.
[7] D. Jido, H. Masutani and S. Hirenzaki, arXiv:1808.1014[nucl-th], accepted to PETP, 2019.
