Tetraquark States

Using the QCD sum rule approach we investigate the possible four-quark structure of the recently observed mesons , firstly observed by BaBaR, and X(3872), firstly observed by Belle. We use diquak-antidiquark currents and work to the order of ms in full QCD, without relying on 1/mc expansion. Our results indicate that a four-quark structure is acceptable for both mesons.