X<sub>0</sub>(2900) and X<sub>1</sub>(2900): Hadronic Molecules or Compact Tetraquarks
Hua-Xing Chen, Wei Chen, Rui-Rui Dong, Niu Su
Abstract
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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mover accent="true"> <mml:mi>c</mml:mi> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> <mml:mover accent="true"> <mml:mi>s</mml:mi> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> <mml:mi>u</mml:mi> <mml:mi>d</mml:mi> </mml:mrow> </mml:math> compact tetraquark state of J P = 1 − . Mass predictions of their bottom partners are also given.