The $T_{bc}$ tetraquarks near the $B\bar{D}$ threshold

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Main Author: Mutuk, Halil
Format: Preprint
Published: 2026
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author Mutuk, Halil
author_facet Mutuk, Halil
contents We study the doubly heavy open-flavor tetraquarks $T_{bc}^{(0)}$ ($J^{P}=0^{+}$) and $T_{bc}^{(1)}$ ($J^{P}=1^{+}$) in the dynamical diquark model, describing the system as a heavy antidiquark--light diquark pair interacting through the lattice-QCD $Σ_g^+(1S)$ Born--Oppenheimer potential. Solving the radial Schrödinger equation yields $M(T_{bc}^{(0)}) = 7.143$--$7.158$ GeV and $M(T_{bc}^{(1)}) = 7.217$--$7.222$ GeV, with hyperfine splittings of $Δ_{HF}\simeq 59$--$79$ MeV. The splitting is driven mainly by the mass difference between symmetric and antisymmetric heavy-antidiquark configurations, while the chromomagnetic interaction contributes linearly with $\partialΔ_{HF}/\partialκ_{\bar b\bar c}=2$, consistent with heavy-antidiquark spin algebra. The mean separation, $\langle r\rangle\simeq 0.45$--$0.46$ fm, and inverse radius, $\langle 1/r\rangle^{-1}\simeq 0.33$--$0.34$ fm, exhibit weak parameter dependence and support a compact diquark--antidiquark interpretation. Relative to open-flavor thresholds, the scalar state lies essentially at the $B\bar D$ threshold and may appear either as a weakly decaying bound tetraquark or as a narrow near-threshold resonance. In contrast, the axial-vector state is consistently predicted as an $S$-wave resonance located $23$--$28$ MeV above $B^{*}\bar D$ and about $70$ MeV below $B\bar D^{*}$, implying a line shape strongly influenced by the nearby $B^{*}\bar D$ threshold.
format Preprint
id arxiv_https___arxiv_org_abs_2605_05150
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The $T_{bc}$ tetraquarks near the $B\bar{D}$ threshold
Mutuk, Halil
High Energy Physics - Phenomenology
High Energy Physics - Experiment
High Energy Physics - Lattice
Nuclear Theory
We study the doubly heavy open-flavor tetraquarks $T_{bc}^{(0)}$ ($J^{P}=0^{+}$) and $T_{bc}^{(1)}$ ($J^{P}=1^{+}$) in the dynamical diquark model, describing the system as a heavy antidiquark--light diquark pair interacting through the lattice-QCD $Σ_g^+(1S)$ Born--Oppenheimer potential. Solving the radial Schrödinger equation yields $M(T_{bc}^{(0)}) = 7.143$--$7.158$ GeV and $M(T_{bc}^{(1)}) = 7.217$--$7.222$ GeV, with hyperfine splittings of $Δ_{HF}\simeq 59$--$79$ MeV. The splitting is driven mainly by the mass difference between symmetric and antisymmetric heavy-antidiquark configurations, while the chromomagnetic interaction contributes linearly with $\partialΔ_{HF}/\partialκ_{\bar b\bar c}=2$, consistent with heavy-antidiquark spin algebra. The mean separation, $\langle r\rangle\simeq 0.45$--$0.46$ fm, and inverse radius, $\langle 1/r\rangle^{-1}\simeq 0.33$--$0.34$ fm, exhibit weak parameter dependence and support a compact diquark--antidiquark interpretation. Relative to open-flavor thresholds, the scalar state lies essentially at the $B\bar D$ threshold and may appear either as a weakly decaying bound tetraquark or as a narrow near-threshold resonance. In contrast, the axial-vector state is consistently predicted as an $S$-wave resonance located $23$--$28$ MeV above $B^{*}\bar D$ and about $70$ MeV below $B\bar D^{*}$, implying a line shape strongly influenced by the nearby $B^{*}\bar D$ threshold.
title The $T_{bc}$ tetraquarks near the $B\bar{D}$ threshold
topic High Energy Physics - Phenomenology
High Energy Physics - Experiment
High Energy Physics - Lattice
Nuclear Theory
url https://arxiv.org/abs/2605.05150