$X_0(2900)$ and $X_1(2900)$: hadronic molecules or compact tetraquarks

TL;DR

This paper investigates the nature of the recently observed $X_0(2900)$ and $X_1(2900)$ tetraquark states, proposing that the former is a hadronic molecule and the latter a compact tetraquark, based on QCD sum rule analysis.

Contribution

It provides a QCD sum rule analysis suggesting specific structural interpretations for the $X_0(2900)$ and $X_1(2900)$ states, including their possible bottom partners.

Findings

$X_0(2900)$ as a $D^{*-}K^{*+}$ molecule

$X_1(2900)$ as a $ar c ar s u d$ compact tetraquark

Predictions for bottom partner masses

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 $\bar c \bar s u d$ compact tetraquark state of $J^P = 1^-$. Mass predictions of their bottom partners are also given.