Analysis of the doubly-charmed tetraquark molecular states with the QCD sum rules

TL;DR

This paper uses QCD sum rules to analyze various doubly-charmed tetraquark molecular states, aiming to identify the nature of the $T_{cc}^+$ state observed by LHCb and predict other possible states.

Contribution

It provides a theoretical assignment of the $T_{cc}^+$ as a $DD^*$ molecular state with specific quantum numbers and predicts additional states for future experimental verification.

Findings

$T_{cc}^+$ likely a $DD^*$ molecular state with $J^P=1^+$, $I=0$

Heavier $DD^*$ molecular states with $J^P=1^+$, $I=1$ remain undetected

Predicted states can be tested against future experimental data

Abstract

In the present work, we investigate the scalar, axialvector and tensor doubly-charmed tetraquark molecular states without strange, with strange and with doubly-strange via the QCD sum rules, and try to make assignment of the $T^+_{cc}$ from the LHCb collaboration in the scenario of molecular states. The predictions favor assigning the $T^+_{cc}$ to be the lighter $DD^{*}$ molecular state with the spin-parity $J^P=1^+$ and isospin $I=0$, while the heavier $DD^{*}$ molecular state with the spin-parity $J^P=1^+$ and isospin $I=1$ still escapes experimental detections, the observation of the heavier $DD^{*}$ molecular state would shed light on the nature of the $T_{cc}^+$. All the predicted doubly-charmed tetraquark molecular states can be confronted to the experimental data in the future.