  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.

Nuclear Theory;High Energy Physics - Phenomenology