Speaker
Description
Kaon-nucleon (KN) interactions with the strangeness $S=+1$ provide a testing ground for comparing lattice QCD with experiments. They also play an important role in understanding the partial restoration of chiral symmetry and in clarifying whether genuine pentaquarks exist. In this study, the S-wave KN interactions are derived using the HAL QCD method with $N_f=2+1$ quark flavors at the physical point, $m_\pi \approx 137$ MeV. We use the configurations generated by the HAL QCD Collaboration, “HAL-conf-2023”. In this talk, we present an updated analysis of the KN interactions, revisiting the results of our previous study [1].
The resulting interaction potential exhibits a purely repulsive behavior for isospin $I=1$, while for $I=0$ a small attractive pocket is observed in addition to repulsion. The obtained phase shifts for $I=1$ agree with experiments at small momenta. In addition, our results indicate that there are no bound or resonant states corresponding to the $\Theta^+$ pentaquark in the S-wave system. Furthermore, we extract the higher-partial-wave phase shifts, ignoring the dependence of the potentials on both spin and angular momentum; the resulting phase shifts deviate significantly from experiment and partial-wave analysis, particularly in the $I=0$, P-wave channel, suggesting a strong attractive contribution from this dependence.
[1] K. Murakami et al. [HAL QCD], Phys. Rev. D 113, no.5, 054506 (2026).