Level crossing of particle–hole and mesonic modes in eta-mesonic nuclei

Abstract

We study eta-meson properties in the infinite nuclear matter and in atomic nuclei with an emphasis on effects of the eta coupling to N * (1535)-nucleon-hole modes. The N * (1535) resonance, which dominates the low-energy eta-nucleon scattering, can be seen as a chiral partner of the nucleon. The change of the chiral mass gap between the N * and the nucleon in a nuclear medium has an impact on the properties of the eta-nucleus system. If the N * -nucleon mass gap decreases with a density increase (chiral symmetry restoration) the calculations show the existence of the resonance state at the energy about 60 MeV and two bound eta-nucleus states with the binding energies about −80 MeV. These states can have strong effect on predicted cross sections of the 12 C(γ , p) 11 B reaction with eta-meson production.

$\eta$ η -nucleus interaction from the d + d reaction around the $\eta$ η

“…21, where the acceptable region of V 0 , W 0 values can be easily understood for each value of the upper limit of the height of the structure in the conversion spectra such as shown in Figs. [17][18][19][20]. From this figure, the upper limit reported in Ref.…”

“…(20). For smaller p 0 value, the distribution of F in the momentum space is more compact and that of f in coordinate space is wider.…”

“…The depth of the socalled tρ potential evaluated by using the η-N scattering length a ηN = (0.28 + 0.19i) fm in Ref. [41] is around − (30,20) MeV at normal nuclear density. It should be noted that the parameters V 0 and W 0 adopted here in Eq.…”

“…Stimulated by this theoretical result, there have been many studies of the structure and the formation reactions of the η mesic nucleus [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. Recently, the η-nucleon and η-nucleus interactions have been studied theoretically in the context of the chiral symmetry of the strong interaction and the η mesic nucleus can be considered as one of the interesting objects to investigate the aspects of the chiral symmetry at finite density [9,12,13,14,15,18,20,23]. As for the experimental studies, the first attempt to observe the η mesic nucleus was performed by the (π + , p) reaction with finite momentum transfer [2], and the interpretation of the data is still controversial [23].…”

Formation ofη-mesic nuclei by the (π,N) reaction and properties ofN*Nagahiro1, Hirenzaki2 2009Phys. Rev. C320180View full textAdd to dashboardCite

“…[20]. Reduction of the mass gap between N and N * causes level crossing of the η and N * -hole modes, and consequently the η spectral function in nuclear medium has significant properties.…”