Phenomenology of K− atoms and other strange hadronic atoms

Abstract

Recent optical-potential studies of the phenomenology of K − atoms are reviewed. It is shown that the data can be fitted by a complex optical potential with either a relatively shallow attractive component (∼ −50 MeV at ρ 0 ), as suggested by a self consistent application of chirally motivated coupled-channels models, or a relatively deep attractive component (∼ −180 MeV at ρ 0 ) as suggested by a mean-field extrapolation of a phenomenological low-density expansion. Both classes of these optical potentials, due to their strongly absorptive component, predict similarly structured relatively narrow 'deeply bound' K − atomic states with widths saturating at about 2 MeV. Possible formation reactions are briefly discussed. The more speculative case for relatively narrow deeply bound K − nuclear states is briefly mentioned. Recent works on other strange hadronic atom systems, for the Σ − and Ξ − hyperons, are also discussed.

Novel halos in light kaonic nuclei as an indicator of nuclear equation of state at supra-normal densities

“…It should be noted that the applicability of chirally motivated models should be restrained by the chiral dynamics to low densities. Whereas both methods need some specific extrapolations to saturation density, diversification appears with a much shallower depth around −50 MeV in both methods 64 , 68 , 71 , 72 . Fortunately, the heavy-ion collisions can provide a direct way to extract the K − potential at appropriately produced densities.…”

Kaons and antikaons in hot and dense hadronic matter

“…The first attempts to extract the antikaon-nucleus potential from the analysis of kaonic-atom data were in favor of very strong attractive potentials of the order of -150 to -200 MeV at normal nuclear matter density ρ 0 [19,20]. However, more recent self-consistent calculations based on a chiral Lagrangian [21,22,23,24] or coupled-channel G-matrix theory (within mesonexchange potentials) [25] only predicted moderate attractive depths of -50 to -80 MeV at density ρ 0 .…”

φ meson mass and decay width in nuclear matter

“…In particular, the φ meson stands as a a unique probe for a possible partial restoration of chiral symmetry in hadronic matter, since it does not overlap with other light resonances in the mass spectrum. In addition, the modification of the φ properties in the medium is strongly related to the renormalization of the kaon properties in the medium, a topic which has also received much attention because of notable deviations from the low density theorem needed to reproduce kaonic atoms data [2,3,4,5] and the possibility of formation of kaon condensates in neutron stars [6]. The φ properties in a nuclear medium could be tested through detection of its decay products in A − A and p − A collisions [7], by means of the reaction π − p → φn in nuclei [8] or the recently proposed method based on inclusive φ photoproduction in nuclei [9].…”