# Few-body approach to structure of $\bar{K}$-nuclear quasi-bound states

## TL;DR

This study employs full few-body calculations to analyze light antikaon-nuclear quasi-bound states, revealing increased central densities and the dependence of ground state spin on the $ar{K}N$ interaction strength.

## Contribution

It provides the first comprehensive few-body analysis of these systems using realistic potentials constrained by experimental data.

## Key findings

- Central nucleon densities increase with antikaon injection.
- The $ar{K}NNNN$ system has the highest central density among studied systems.
- Ground state spin depends on the $ar{K}N$ attraction strength.

## Abstract

Structure of light antikaon-nuclear quasi-bound states, which consist of an antikaon $(\bar{K}=K^-,~\bar{K}^0)$ and a few nucleons $(N=p,~n)$ such as $\bar{K}NN$, $\bar{K}NNN$, $\bar{K}NNNN$ and $\bar{K}NNNNNN$ systems, is studied with full three- to seven-body calculations. Employing a realistic $\bar{K}N$ potential based on the chiral SU(3) effective field theory with the SIDDHARTA constraint, we show that the central nucleon densities of these systems increases when the antikaon is injected, by about factor of two at maximum. The $\bar{K}NNNN$ system shows the largest central density, about 0.74 fm$^{-3}$ even with the phenomenological $\bar{K}N$ potential, which are not as high as those suggested in previous studies with approximate treatments of the few-body systems. We find the spin of the ground state of the $\bar{K}NNNNNN$ system depends on the strength of the $\bar{K}N$ attraction. Thus, the quantum number of the ground state can be another constraint on the $\bar{K}N$ interaction.