Born-Oppenheimer chiral effective field theory and its application to Xb
Abstract
Following the discovery of the exotic state X(3872) in the charmonium spectrum, the possible existence of an analogous state, Xb, in the bottomonium sector has attracted considerable attention of the hadronic physics community. In this work, we lay the ground for the development of Born-Oppenheimer chiral effective field theory (BOχEFT), that allows us to include both quark and hadron degrees of freedom as well as the full complexity of the meson-exchange potential in a systematic way. For illustration, the formalism to leading order (LO) is applied to the system of χb1 states and in particular the Xb. The two parameters that are present at this order are constrained using experimental information on the bottomonium spectrum together with lattice input on static quark-antiquark potentials, including string breaking effects. The framework identifies the observed 1++ state at 10.513 GeV with a predominantly molecular Xb, the bottom counterpart of the X(3872), and predicts an additional predominantly compact bottomonium state at 10.544 GeV, about 60 MeV below the BB̅* threshold.
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BibTeX
@misc{zhang2026bornoppenheimer,
title = {{Born-Oppenheimer chiral effective field theory and its application to $X_b$}},
author = {Yu Zhang and Feng-Kun Guo and Christoph Hanhart and Alexey Nefediev and Paul Pütz},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.19066},
eprint = {2610.19066},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.19066},
}
RIS
TY - UNPB
TI - Born-Oppenheimer chiral effective field theory and its application to X_b
AU - Yu Zhang
AU - Feng-Kun Guo
AU - Christoph Hanhart
AU - Alexey Nefediev
AU - Paul Pütz
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.19066
UR - https://arxiv.org/abs/2610.19066
AB - Following the discovery of the exotic state X(3872) in the charmonium spectrum, the possible existence of an analogous state, X_b, in the bottomonium sector has attracted considerable attention of the hadronic physics community. In this work, we lay the ground for the development of Born-Oppenheimer chiral effective field theory (BOχEFT), that allows us to include both quark and hadron degrees of freedom as well as the full complexity of the meson-exchange potential in a systematic way. For illustration, the formalism to leading order (LO) is applied to the system of χ_b1 states and in particular the X_b. The two parameters that are present at this order are constrained using experimental information on the bottomonium spectrum together with lattice input on static quark-antiquark potentials, including string breaking effects. The framework identifies the observed 1^++ state at 10.513 GeV with a predominantly molecular X_b, the bottom counterpart of the X(3872), and predicts an additional predominantly compact bottomonium state at 10.544 GeV, about 60 MeV below the BB̅^* threshold.
ER -