Study of pentaquarks on the lattice with overlap fermions

We present a quenched lattice QCD calculation of spin-$1/2$ five-quark states with $uudd\overline{s}$ quark content for both positive and negative parities. We do not observe any bound pentaquark state in these channels for either $I=0$ or $I=1$. The states we found are consistent with $KN$ scattering states which are checked to exhibit the expected volume dependence of the spectral weight. The results are based on overlap-fermion propagators on two lattices, ${12}^3\times 28$ and ${16}^3\times 28$, with the same lattice spacing of 0.2 fm, and pion mass as low as $\sim 180\mathrm{M}\mathrm{e}\mathrm{V}$.