Speaker
Prof.
Satoru Hirenzaki
(Nara Women's University)
Description
The study of the spontaneous breaking of chiral symmetry and its partial restoration at finite density based on the studies of the Mesic Atoms and Mesic Nuclei is one of the important branch of modern Hadron Nuclear Physics [1,2]. We try to proceed this research field to investigate the U_A(1) anomaly effects in the nuclear medium by
studying the eta'(958) Mesic nuclei. The present exploratory level of the U_A(1) anomaly effects at finite density is rather poor since there exists no experimental
information on the possible effective restoration of the U_A(1) anomaly in nucleus, though some theoretical results have been reported long ago [3,4]. Since the huge eta'(958) mass is believed to have a very close connection to the U_A(1) anomaly, the eta'(958) mass in the medium should provide us with important information on the effective restoration of the U_A(1) anomaly. In this context, the eta'(958) mesic nuclei is considered to be one of the most interesting systems [5,6].
We report two important points in this talk; (i) the possible existence of the quasi-stable eta'(958) bound states with significantly small decay widths, and (ii) the theoretical predictions for the formation of the eta'(958) mesic nuclei relevant to the actual experiments.
The possibility of the existence of the quasi-stable states is theoretically considered recently [7]. The eta'(958) mass is considered to be generated by the U_A(1) anomaly which picks up the chiral condensate around to give the extra mass for eta'(958). Hence, we expect the mass reduction of the eta'(958) at finite density because of the reduced condensate there. In this talk, we point out the possibility to have no (or small) imaginary part of the selfenergy accompanied by the mass reduction mechanism through the U_A(1) anomaly. As the consequence, we have the possibility to have strong attractive interaction with small imaginary part between eta'(958) and nucleus, which ensures us to have quasi-stable eta'(958) bound states.
We will also report the expected formation spectra of the eta'(958) mesic nuclei. We have made the comprehensive predictions for the formation by the photon [5,6] and pion [8] beams using the Green's function methods.
[1] K. Suzuki $et$ $al$., Phys. Rev. Lett. 92, 072302 (2004).
[2] D. Jido, T. Hatsuda, and T. Kunihiro, Phys. Lett. B670, 109 (2008).
[3] R. D. Pisarski and F. Wilczek, Phys. Rev. D29, 338 (1984).
[4] T. Kunihiro, Phys. Lett. B219, 363 (1989).
[5] H. Nagahiro and S. Hirenzaki, Phys. Rev. Lett. 94, 232503 (2005).
[6] H. Nagahiro, M. Takizawa and S. Hirenzaki, Phys. Rev. C74, 045203 (2006).
[7] D. Jido, H. Nagahiro, S. Hirenzaki, in preparation.
[8] H. Nagahiro, Prog. Theor. Phys. Suppl. 186, 316 (2010).
Primary author
Prof.
Satoru Hirenzaki
(Nara Women's University)
Co-authors
Dr
Daisuke Jido
(Kyoto University)
Dr
Hideko Nagahiro
(Nara Women's University)
