Regular Article - Theoretical Physics
The pentaquark from a combined effective field theory and phenomenological perspective
School of Physics, Beihang University, 100191, Beijing, China
2 Centre d’Études Nucléaires, CNRS/IN2P3, Université de Bordeaux, 33175, Gradignan, France
3 International Research Center for Nuclei and Particles in the Cosmos and Beijing Key Laboratory of Advanced Nuclear Materials and Physics, Beihang University, 100191, Beijing, China
Accepted: 5 July 2021
Published online: 29 July 2021
The observation of the by the LHCb collaboration adds a new member to the set of known hidden-charm pentaquarks, which includes the , and . The is expected to have the light-quark content of a baryon (, ), but its spin is unknown. Its closeness to the threshold – in the isospin-symmetric limit – suggests the molecular hypothesis as a plausible explanation for the . While in the absence of coupled-channel dynamics heavy-quark spin symmetry predicts the two spin-states of the to be degenerate, power counting arguments indicate that the coupling with the nearby and channels might be a leading order effect. This generates a hyperfine splitting in which the pentaquark will be lighter than the configuration, which we estimate to be of the order of . We also point out an accidental symmetry between the and potentials. Finally, we argue that the spectroscopy and the decays of the might suggest a marginal preference for over .
© The Author(s) 2021
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Funded by SCOAP3