Tetraquarks with colour-blind forces in chiral quark models

We discuss the stability of multiquark systems within the recent model of Glozman et al. where the chromomagnetic hyperfine interaction is replaced by pseudoscalar-meson exchange contributions. We find that such an interaction binds a heavy tetraquark systems QQqq (Q = c, b and q = u, d) by 0.2–0.4 GeV. This is at variance with results of previous models where ccqq is unstable.