Searching for tetraquarks on the lattice

We address the question whether the lightest scalar mesons σ and κraquarks. We present a search for possible light tetraquark states with JPC = 0++ and I = 0, 1/2, 3/2, 2 in the dynamical and the quenched lattice simulations using tetraquark interpolators. In all the channels, we unavoidably find lowest scattering states π (k) π (-k) or K(k) π (-k) with back-to-back momentum k = 0, 2 π /L,. However, we find an additional light state in the I = 0 and I = 1/2 channels, which may be related to the observed resonancesπ and π with a strong tetraquark component. In the exotic repulsive channels I = 2 and I = 3/2, where no resonance is observed, we find no light state in addition to the scattering states.