K−N amplitudes below threshold constrained by multinucleon absorption

Abstract

Six widely different subthreshold K − N scattering amplitudes obtained in SU(3) chiral-model EFT approaches by fitting to low-energy and threshold data are employed in optical-potential studies of kaonic atoms. Phenomenological terms representing K − multinucleon interactions are added to the EFT-inspired single-nucleon part of the K − -nucleus optical potential in order to obtain good fits to kaonic-atom strong-interaction level shifts and widths across the periodic table. Introducing as a further constraint the fractions of single-nucleon K − absorption at rest from old bubble-chamber experiments, it is found that only two of the models considered here reproduce these absorption fractions. Within these two models, the interplay between single-nucleon and multinucleon K − interactions explains features observed previously with fully phenomenological optical potentials. Radial sensitivities of kaonic atom observables are re-examined, and remarks are made on the role of 'subthreshold kinematics' in absorption-at-rest calculations.

Calculations of kaonic nuclei based on chiral meson-baryon coupled-channel interaction models

“…The binding energies B K − exhibit the same A dependence in all models considered, however, their magnitudes are strongly model dependent. It is due to the different depths of ReV (1) K − predicted by the K − N interaction models. The K − N conversion widths are rather small and weakly A-dependent.…”

“…The parameters of the phenomenological potential, complex amplitude B and positive exponent α, were recently fitted by Friedman and Gal [1] to kaonic atom data for each chirally-motivated meson-baryon interaction model considered in this work separately. Moreover, the total…”

“…The kaonic atom data probe the K − optical potential up to at most ∼ 50% of the nuclear density [1]. Further inside the nucleus, the shape of the potential is just an analytical continuation of the formula.…”

“…They yield quite diverse K − 1s binding energies and rather small K − decay widths. Next, we supplement the K − single-nucleon potential by a phenomenological K − multinucleon potential introduced recently to achieve good fits to kaonic atom data [1]. We demonstrate a decisive impact of the K − multinucleon interactions on the widths of K − -nuclear states.…”

“…The K − singlenucleon potential is supplemented by a phenomenological K − multinucleon potential fitted recently to kaonic atom data for each of the chiral models separately [1]. In Section 2, we briefly introduce the kaon self-energy operator including in-medium modifications of the underlying K − N scattering amplitudes and demonstrate how to incorporate strong energy and density dependence of the inmedium amplitudes in self-consistent calculations of kaonic nuclei.…”