From kaon-nuclear interactions to kaon condensation

Abstract

An effective chiral Lagrangian in heavy-fermion formalism whose parameters are constrained by kaon-nucleon and kaon-nuclear interactions next to the leading order in chiral expansion is used to describe kaon condensation in dense "neutron star" matter. The critical density is found to be robust with respect to the parameters of the chiral Lagrangian and comes out to be ρ c ∼ (3 − 4)ρ 0 . Once kaon condensation sets in, the system is no longer composed of neutron matter but of nuclear matter. Possible consequences on stellar collapse with the formation of compact "nuclear stars" or light-mass black holes are pointed out.

Kaon condensation in “nuclear star” matter

“…As remarked above, there are compensating effects such as the screening of the vector channel which has to be considered on the same footing, so a fully consistent treatment would require more work. What is fairly certain is that although the detailed mechanism appears quite different here from that in the low-order treatments, once the condensation sets in, the rest of the star properties are expected to resemble closely the structure obtained in [6,7]. A detailed analysis of the "nuclear star" that we obtained in this paper will be made elsewhere.…”

“…Ever since the seminal paper of Kaplan and Nelson [2], there have been numerous investigations on kaon condensation in dense neutron star matter as well as in nuclear matter based both on effective chiral Lagrangians [3,4,5,6,7] and on phenomenological off-shell meson-nucleon interactions [8,9]. The results have been quite confusing: While the chiral Lagrangian calculations generally predict a relatively low critical density, ρ c ∼ (2 − 4)ρ 0 , the phenomenological approaches have indicated that a kaon condensation at such a low density may be incompatible with kaon-nucleon data and in some versions seem to exclude any condensation at al.…”

Dmesons in nuclear matter: ADNcoupled-channel equations approach

“…But as touched on later, the latter arises from vector-meson exchanges between D and N in the low-energy and low-momentum-transfer limit as inferred from the hidden local symmetry picture of vector mesons [22] or from the success, for example, of the ρ-ω model for the KN interaction [23] (see also Ref. [24]). So at finite nuclear density there may well be some double counting in the vector-meson exchange contribution.…”

ϕ decay: A relevant source forK−production at energies available at the GSI Schwerionen-Synchrotron (SIS)?

“…The systematic study of K ± subthreshold production yields, phase space distributions, and flow observables in relativistic heavy-ion collisions at various beam energies and for various system sizes and centralities has attracted much attention, in particular in the context of in-medium properties of K + and K − mesons [1][2][3][4][5][6][7][8][9][10]. Corresponding experiments have been the focus of studies by the KaoS [11][12][13][14][15] and FOPI [16][17][18][19][20] Collaborations over the last two decades, following up on the pioneering experiments at Bevalac [21].…”

“…Indeed, the combined analysis of K + and K − suggests that a substantial part of the observed K − mesons is due to a strangeness exchange mechanism [33]. Furthermore K + and K − exhibit distinctively different in-medium properties, both in theoretical approaches [1][2][3][4][5][6][7][8][9][10][31][32][33][34] and in experiments [11][12][13]15,18,19,22].…”