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Description
Interactions between a kaon and nucleon provide an essential input for understanding the partial restoration of chiral symmetry and the properties of pentaquarks. Although kaon-nucleon scattering experiments at low momenta have been performed since the 1960s, our understanding of these interactions remains limited due to the scarcity of experimental data near the threshold, which hampers a precise elucidation of the underlying physics. On the other hand, recent advances in computational resources and lattice QCD techniques have made it possible to determine hadron interactions from first principles.
In this study, we investigate the S-wave kaon-nucleon interactions in lattice QCD using the time-dependent HAL QCD method. The calculation is performed with $N_f=2+1$ quark flavors at the physical point, $m_{\pi}\approx 137$ MeV. The resulting interaction potential exhibits repulsive (weak attractive) behavior in the isospin $I=1$ ($I=0$) channel. The extracted phase shifts indicate the absence of bound or resonant states corresponding to the $\Theta^{+}$ pentaquark in this system.