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

Abstract

Very recently the LHCb collaboration reported their observation of the first two fully open-flavor tetraquark states, the X0(2900) of JP = 0+ and the X1(2900) of JP = 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 X1(2900) has a width significantly larger than the lower one X0(2900). Our results suggest that the X0(2900) can be interpreted as the s-wave D*–K*+ molecule state of JP = 0+, and the X1(2900) can be interpreted as the p-wave compact tetraquark state of JP = 1−. Mass predictions of their bottom partners are also given.