Bridging doubly heavy tetraquark mass spectrum with heavy baryons utilizing heavy antiquark-diquark symmetry

Motivated by the observation of the doubly charmed tetraquark $T_{cc}(3875)^+$, we present a systematic study of double heavy tetraquarks ($T_{QQ’\bar{q}\bar{q}’}$) using heavy antiquark-diquark symmetry (HADS) within a constituent quark model. By calibrating model parameters to known hadron spectra and incorporating the effective mass formula, we predict the masses for 38 ground-state tetraquarks with $cc$, $bb$, and $bc$ heavy quark pairs, including the non-strange, single-strange, and double-strange configurations with quantum numbers $J^P = 0^+, 1^+$ and $2^+$. Notably, we identify several stable states below the relevant meson-meson thresholds, particularly in the $bb\bar{q}\bar{q}’$ sector. The explicit connection between doubly heavy tetraquark and heavy baryon spectra through HADS reduces model dependence and reveals fundamental systematics in the heavy-quark hadron landscape.

💡 Research Summary

The paper presents a comprehensive study of doubly‑heavy tetraquarks (DHTs) (T_{QQ’\bar q\bar q’}) using Heavy Antiquark‑Diquark Symmetry (HADS) within a constituent quark model (CQM). The motivation is the recent observation of the doubly‑charmed tetraquark (T_{cc}(3875)^+) by LHCb, which has sparked intense debate over whether such states are compact multiquarks or loosely bound hadronic molecules. The authors argue that the pattern of partner states can discriminate between these pictures, and they set out to predict the full ground‑state spectrum of DHTs with heavy‑quark pairs (cc), (bb), and (bc) and with non‑strange, single‑strange, and double‑strange light‑quark configurations.

Theoretical framework
HADS is the central organizing principle. In the limit of infinitely heavy quarks, a color‑antitriplet heavy diquark ((QQ’)) behaves like a static color‑triplet heavy antiquark (\bar Q). Consequently, the dynamics of a compact tetraquark ((QQ’\bar q\bar q’)) can be mapped onto those of a heavy‑light meson ((\bar Q q)) or a doubly‑heavy baryon ((QQ’ q)). This mapping allows the authors to import the well‑tested CQM parameters that describe meson and baryon spectra directly into the tetraquark sector, dramatically reducing model dependence.

The CQM mass formula used for baryons is
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