Single- and two-nucleon antikaon absorption in nuclear matter with chiral meson-baryon interactions

Abstract

We have developed a microscopic model for antikaon absorption on two nucleons in nuclear matter. The absorption is described within a meson-exchange picture and the primary K − N interaction strength is derived from state-of-the-art chiral coupled channel meson-baryon interaction models. We took into account the medium modification of the K − N scattering amplitudes. We derived the K − N N as well as K − N optical potentials as functions of nuclear matter density including the real part of the K − N N potential. We calculated the K − single-and two-nucleon absorption fractions and branching ratios for various mesonic and non-mesonic channels. We have confirmed the crucial role of in-medium effects in our calculations. Our results are in very good agreement with available experimental data from old bubble chamber experiments as well as with the latest results from the AMADEUS collaboration. I = 0 resonance Λ(1405), which couples strongly to the πΣ channel giving rise to a sizable K − absorption. The theoretical description of the K − N interaction is currently provided by the chiral coupled channel meson-baryon interactions models [11][12][13][14][15] in which the Λ(1405) is generated dynamically. Parameters of these models are fitted to available low-energy K − N observables [16][17][18][19][20][21]. On the other hand, the interaction of antikaons with two and more nucleons lacks a solid theoretical description.A very important source of information about the K − -nucleus interaction is provided by kaonic atom experiments, in which the low-energy K − annihilates in the surface region of a nucleus, thereby probing the K − -nucleus potential at low nuclear densities close to threshold. The latest analysis of kaonic atom data by Friedman and Gal [22] showed that K − optical potentials based on the K − N scattering amplitudes derived from state-of-the-

On the $$\hbox {K}^{-}$$ Absorptions in Light Nuclei by AMADEUS

“…in agreement with the theoretical calculations (BCN model) given in Ref. [33] at 0.3 ρ 0 baryon density, which is the relevant density region for the absorption of low-energy K − on 12 C nuclei. Based on the measured BRs (Ref.…”

“…[34]) and combining the theoretical/experimental information available in the literature (Refs. [33,44]) a missing contribution of (5.5 ± 0.1(stat.) +1.0 −0.9 (syst.…”

“…Moreover the total K − 2NA branching ratio (BR) is also calculated in Ref. [33]. Such novel theoretical findings demand comparisons with new, high precision, experimental values of yields and low-energy cross sections for those rare K − multinucleon interaction reactions which were never singled out in the available bubble chamber data.…”

“…An upgrade in the treatment of the K − two-nucleon absorption (K − 2NA) based on a microscopic description of the three body problem is given in Refs. [32,33]. Moreover the total K − 2NA branching ratio (BR) is also calculated in Ref.…”

The K¯N Interaction in Higher Partial Waves

“…Since our previous works obtained a reasonable reproduction of the experimental data with pure s-wave scattering amplitudes [28][29][30], the importance of the higher partial waves would also imply that their physics would have been masked in the values of the NLO parameters obtained in these studies. In addition, extending theKN interaction to p-wave components is also relevant for studies of boundK mesons in nuclei [32][33][34][35], since their local momentum can acquire sizable values. The p-wave components of theKN interaction can also play a non-negligible role in the phenomenon of kaon condensation in neutron stars, since the nuclear densities involved imply relatively large nucleon momenta.…”