A state built from meson dynamics
A theoretical preprint proposes that X(2370) can emerge from the interaction of the phi meson with h1(1380), itself treated as a K* Kbar molecular state. The calculation gives the generated state a mass of 2316 ± 10 MeV and a width of 163 ± 31 MeV, values the authors describe as in line with X(2370). The width describes how broadly the calculated resonance is spread across mass. The state is also reported to have the same quantum numbers as X(2370), meaning the same classification labels used to describe its basic properties.
To test the idea, the authors calculate the phi-cluster interaction with a fixed-center approximation that implements elastic unitarity. They then compare the calculated line shape, meaning how the predicted signal changes across mass, with experimental data identified as coming from Ref. [27].
For that comparison, the resonant contribution is added incoherently to a third-order nonresonant polynomial. The polynomial coefficients and the relative weight of the resonant contribution are fitted to the data. This leaves the calculation describing both a proposed resonance pattern and a fitted background shape.
A two-peak pattern and a distinctive decay story
The calculated line shape contains two notable features. One peak appears around 2050 MeV and is associated with K(1630). A second, around 2300 MeV, is interpreted as a genuine generated state. The authors use the pair of features to connect the mass distribution with both K(1630) dynamics and the proposed phi-h1(1380) state.
The model also makes a qualitative prediction about decays. It presents the gamma-omega, gamma-phi and K* Kbar channels as naturally suppressed, while the non-K* Kbar K Kbar pi contribution is strongly enhanced. The proposed explanation invokes a triangle singularity in the modeled decay process and a K(1630) resonance that couples strongly to phi-rho and decays to K Kbar.
That pattern is part of the authors' case for the molecular interpretation. It remains a model explanation of the observed behavior, built around the assumed phi-h1(1380) dynamics, rather than a direct determination of the particle's internal structure.
Predictions that could test the proposal
The authors identify further mass distributions as a way to test the proposal. Their calculation predicts large contributions near 1830 MeV in the K Kbar mass and about 1912 MeV in the pi K mass. The supplied analysis says those distributions were not reported in the experimental paper, so they remain predictions rather than confirmed features.
To estimate how much the result depends on its inputs, the study generates uncertainty bands by randomly varying the masses of h1(1380), K1(1400) and K(1630), the widths of K1(1400) and K(1630), and the K1(1400)-to-phi K coupling. The paper also says its input amplitudes were borrowed from earlier works and describes the calculation as parameter-free within its uncertainty treatment. The quoted mass and width are therefore model outputs, not direct experimental determinations.
The central assumption is structural: h1(1380) is treated as a K* Kbar molecule, and X(2370) is treated as a state generated from its interaction with phi. The evidence supplied for the claim is consequently a theoretical model and its comparison with a cited mass distribution. Whether the predicted K Kbar and pi K structures appear in future measurements remains an open test of the proposal.
The document is an arXiv v1 preprint dated 29 September 2026.
Paper data and sources
Original title: A glueball puzzle explained in terms of $φh_1(1380)$ dynamics: Aka $X(2370)$
Authors: K. P. Khemchandani, A. Martinez Torres, E. Oset
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-09-29
DOI: Not available
Original paper · Full text