X0 (2900) and X1 (2900): Hadronic Molecules or Compact Tetraquarks

Very recently the LHCb collaboration reported their observation of the first two fully open-flavor tetraquark states, the X-0 (2900) of J(P) = 0(+) and the X-1 (2900) of J(P) = 1(-). We study their possible interpretations using the method of QCD sum rules, paying special attention to an interesting feature of this experiment that the higher resonance X-1 (2900) has a width significantly larger than the lower one X-0 (2900). Our results suggest that the X-0 (2900) can be interpreted as the s-wave D*K-*(+) molecule state of J(P) = 0(+), and the X-1 (2900) can be interpreted as the p-wave egud compact tetraquark state of J(P) = 1(-) Mass predictions of their bottom partners are also given.