Doubly Heavy Tetraquarks in the Born-Oppenheimer approximation

TL;DR

This paper applies the Born-Oppenheimer approximation to study doubly heavy tetraquarks, successfully predicting masses and providing insights into their structure and experimental observations.

Contribution

It introduces a novel application of the Born-Oppenheimer approximation to tetraquarks and predicts the mass of the Tbb state based on this method.

Findings

Successfully computed the Tcc tetraquark mass using two different approaches.

Predicted the Tbb tetraquark mass with the same method.

Estimated tetraquark sizes to be 3-5 GeV^-1, indicating small hyperfine effects.

Abstract

Tetraquarks QQq*q* are found to be described remarkably well with the Quantum Chromodynamics version of the Hydrogen bond, as treated with the Born-Oppenheimer approximation. We show the robustness of the method by computing the mass of the observed Tcc tetraquark following two different paths. Relying on this, we provide a prediction for the mass of the expected Tbb particle. The average sizes of tetraquarks are estimated to be approximately 3 - 5 GeV**-1. As a consequence hyperfine separations are not expected to be sizeable. We discussed possible reasons why LHCb has observed only one state in the DD* spectrum.