Quarkoniumlike states above open-flavor thresholds in Born-Oppenheimer EFT
Abstract
Many quarkoniumlike states have been observed above open-flavor thresholds, but their organization and internal structure remain unsettled. We study the isoscalar hidden-charm and hidden-bottom sectors in Born--Oppenheimer effective field theory (BOEFT), between the spin--isospin averaged S+S and S+P thresholds. At leading order, heavy-quark spin decouples, and the quarkonium static potential mixes through string breaking with the lowest tetraquark/open-flavor BO potentials of the same quantum numbers. These potentials are constrained by QCD symmetries, their short- and long-distance behavior, and lattice-QCD data. The only calibrated parameter is the lowest 1−− adjoint meson mass, fixed from the shallow multiplet associated with the χc1(3872). Using T-matrix, K-matrix, and complex-scaling methods, we determine bound states and resonance poles, their masses, pole widths from the included nonstrange S+S channels, normalized pole couplings, and prescription-dependent quarkonium--open-flavor composition measures. The spectrum exhibits a common heavy-quark-spin-symmetry multiplet organization. Most poles are short-distance, predominantly quarkonium resonances. The same equations generate shallow, spatially extended, open-flavor-dominated states with molecular long-distance characteristics. Their binding energies, radii, and small quarkonium components are highly sensitive to the adjoint meson mass, whereas the higher spectrum is more stable. The equations also predict a more compact open-flavor-dominated resonance in the l = 0 bottomoniumlike sector, with a dominant P-wave open-flavor component. Together with the hybrid levels, the spectrum provides multiplet assignments for most candidates. States not naturally accommodated point to the need for hidden-strange and S+P tetraquark/open-flavor BO sectors and for hybrid--tetraquark and hybrid--quarkonium mixings.
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BibTeX
@misc{brambilla2026quarkoniumlike,
title = {{Quarkoniumlike states above open-flavor thresholds in Born-Oppenheimer EFT}},
author = {Nora Brambilla and Roberto Bruschini and Abhishek Mohapatra and Fang-Zheng Peng and Tommaso Scirpa},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2608.04105},
eprint = {2608.04105},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.04105},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Quarkoniumlike states above open-flavor thresholds in Born-Oppenheimer EFT
AU - Nora Brambilla
AU - Roberto Bruschini
AU - Abhishek Mohapatra
AU - Fang-Zheng Peng
AU - Tommaso Scirpa
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2608.04105
UR - https://arxiv.org/abs/2608.04105
AB - Many quarkoniumlike states have been observed above open-flavor thresholds, but their organization and internal structure remain unsettled. We study the isoscalar hidden-charm and hidden-bottom sectors in Born--Oppenheimer effective field theory (BOEFT), between the spin--isospin averaged S+S and S+P thresholds. At leading order, heavy-quark spin decouples, and the quarkonium static potential mixes through string breaking with the lowest tetraquark/open-flavor BO potentials of the same quantum numbers. These potentials are constrained by QCD symmetries, their short- and long-distance behavior, and lattice-QCD data. The only calibrated parameter is the lowest 1^−− adjoint meson mass, fixed from the shallow multiplet associated with the χ_c1(3872). Using T-matrix, K-matrix, and complex-scaling methods, we determine bound states and resonance poles, their masses, pole widths from the included nonstrange S+S channels, normalized pole couplings, and prescription-dependent quarkonium--open-flavor composition measures. The spectrum exhibits a common heavy-quark-spin-symmetry multiplet organization. Most poles are short-distance, predominantly quarkonium resonances. The same equations generate shallow, spatially extended, open-flavor-dominated states with molecular long-distance characteristics. Their binding energies, radii, and small quarkonium components are highly sensitive to the adjoint meson mass, whereas the higher spectrum is more stable. The equations also predict a more compact open-flavor-dominated resonance in the l = 0 bottomoniumlike sector, with a dominant P-wave open-flavor component. Together with the hybrid levels, the spectrum provides multiplet assignments for most candidates. States not naturally accommodated point to the need for hidden-strange and S+P tetraquark/open-flavor BO sectors and for hybrid--tetraquark and hybrid--quarkonium mixings.
ER -