Scientists are currently investigating the molecular nature of the Υ(11020) particle, seeking to confirm predictions made by heavy-quark symmetry regarding a corresponding molecular partner. Qing Lu from Yibin University, Cai Cheng from Sichuan Normal University, and Yin Huang from Southwest Jiaotong University, along with their colleagues, propose that the observed Υ(11020) represents a candidate for this elusive state, potentially comprising a specific SS-wave configuration. Their research interprets the Υ(11020) as a B₁BB₁B or B₁BB₁B molecular state, utilising the compositeness condition and effective Lagrangians to analyse its strong decay widths. This work is significant because identifying the decay patterns, particularly a dominant decay into Υ(1S), would provide compelling evidence for the molecular structure of the Υ(11020) and rigorously test the principles of heavy-quark symmetry.
Υ(11020) as a potential bottom meson molecule challenges conventional bottomonium structure and necessitates further investigation
Scientists have identified a potential molecular state within particle physics, offering new insights into the strong force that governs the interactions of quarks. Research published recently proposes that the Υ(11020) particle, previously categorised as a conventional bottomonium state, may instead be a molecule composed of a bottom meson and its excited partner.
This interpretation challenges the standard understanding of Υ(11020)’s structure and opens avenues for testing fundamental symmetries within the Standard Model. The work centres on the idea that certain hadrons exhibit more complex internal structures than previously thought, moving beyond the simple quark-antiquark pairing.
Researchers calculated the strong decay widths of the Υ(11020) particle, assuming it behaves as a B1 B, B1 B∗ molecule, utilising the compositeness condition and effective Lagrangians. By fitting experimental data from Υ(11020) decays into electron-positron pairs and chi-b mesons with pions, the team extracted the coupling strength between the Υ(11020) and its constituent B1 and B∗ mesons.
These couplings were then used to predict the rates at which the Υ(11020) would decay into various combinations of B mesons and pions, including both two-body and three-body decay channels. The results indicate that the Υ(11020) is predominantly a molecule with a strong B1 B component, with its primary decay mode being B∗ s B∗.
Partial decay widths into Υ(nS) and hb(nP) mesons were found to be exceptionally narrow, measuring only a few electron volts. Conversely, decays involving three pions exhibited significantly larger widths, reaching 0.167 MeV for the χb1 channel and a predicted 0.754 keV for the currently unobserved χb0 channel.
These distinctive decay patterns are proposed as clear experimental signatures of the molecular nature of the Υ(11020). Confirmation of these predictions would not only validate the molecular interpretation of the Υ(11020) but also provide a crucial test of heavy-quark symmetry, a fundamental principle in particle physics.
Heavy-quark symmetry predicts relationships between particles containing heavy quarks, such as bottom quarks, and this work offers a means to verify its applicability to exotic hadronic states. The study builds upon previous observations of molecular states like the X(3872) and Λ(1405), extending the concept to the heavier bottom-quark sector and potentially revealing a new class of molecular hadrons.
Υ(11020) decay width analysis via constituent meson couplings and resonant states reveals important insights into strong interaction dynamics
Researchers began by interpreting the Υ(11020) particle as a bound state comprised of a B1B, B1B∗ molecule, employing the compositeness condition and effective Lagrangians to calculate its strong decay widths. Existing experimental data, specifically Υ(11020) decays into e+e− and χbJπππ, were fitted to extract the couplings between the Υ(11020) and its constituent B1 and B(∗) mesons.
These extracted couplings then facilitated the calculation of partial decay widths for various channels, including B(∗) (s) B(∗) (s), ππΥ(nS), ππhb(nP), and πππχb1, utilising hadronic loops and tree-level diagrams for three-body B∗πB(∗) decays. The study determined that the Υ(11020) is predominantly a B1B molecule, constituting approximately 75.4% of its total composition.
Decays of the Υ(11020) into ππΥ(nS) and ππhb(nP) were found to proceed via intermediate resonances Zb and Z′b, resulting in partial widths of only a few eV. In contrast, the πππχbJ channels exhibited significant enhancement, with the πππχb1 final state reaching 0.167 MeV, while the unobserved πππχb0 channel was calculated to be 0.754 keV.
Calculations of the B∗sB∗s decay channel yielded a partial width of 0.418 MeV at Λ = 0.615 GeV, differing substantially from K-matrix analyses of e+e− annihilation data which indicate a BsBs decay channel accounting for 70%, 90% of the total width. Furthermore, the work contrasts with non-relativistic quark model predictions, which typically predict a dominant B∗B∗ decay channel exceeding 50%, whereas this study found it contributed only a small fraction to the total width. These distinctive decay patterns are proposed as crucial experimental signatures to validate the molecular nature of the Υ(11020) and test heavy-quark symmetry at facilities like LHCb.
Υ(11020) decay characteristics support predominantly molecular B1B composition, consistent with theoretical predictions
Partial widths for the Υ(11020) decaying into B(∗) (s) B(∗) (s), ππΥ(nS ), ππhb(nP), and πππχbJ were calculated using extracted couplings and hadronic loops. Results demonstrate that the Υ(11020) exhibits characteristics consistent with a predominantly molecular structure, specifically a B1 B, B1 B∗ molecule with a dominant B1 B component.
The primary decay channel for this molecule is identified as B∗ s B∗. Partial widths for decays into ππΥ(nS ) and ππhb(nP) were found to be only a few eV, indicating a suppressed decay rate. In contrast, the widths for Υ(11020) decaying into πππχbJ are considerably larger, reaching 0.167 MeV for the πππχb1 channel.
The unobserved πππχb0 channel is predicted to have a width as large as 0.754 keV, offering a potential avenue for experimental verification. These distinctive decay patterns provide clear experimental signatures indicative of the molecular nature of the Υ(11020). Confirmation of these patterns would serve as a robust test of the applicability of heavy-quark symmetry within this system.
This work interprets the Υ(11020) as a B1 B, B1 B∗ molecule, determining the coupling between the Υ(11020) and its constituent B1 and B(∗) mesons by fitting experimental data from Υ(11020) →e+e− and Υ(11020) →χbJπππ decays. The study then computes partial decay widths for various channels, including those involving hadronic loops and three-body decays via tree-level diagrams. The calculated widths provide a detailed picture of the Υ(11020)’s decay dynamics and support its interpretation as a molecular state.
Υ(11020) decay characteristics support a B1B(∗) molecular structure consisting of two bottom quarks
Researchers have investigated the potential molecular nature of the Υ(11020) resonance, proposing it may be a bound state composed of B1 and B(∗) mesons. This analysis centres on examining the decay patterns of the Υ(11020) to ascertain if they align with expectations for a molecular configuration. By treating the Υ(11020) as a B1B(∗) molecule, calculations of its strong decay widths were performed using established theoretical frameworks, including effective Lagrangians and the compositeness condition.
The results demonstrate that the Υ(11020) exhibits characteristics consistent with being predominantly a molecule, with a primary decay mode into two B mesons. Calculated decay widths into various final states reveal distinctive patterns; decays into certain combinations of mesons are predicted to be significantly smaller than others, specifically a width of 0.167 MeV for one channel and a much smaller value of 0.754 keV for another.
These unique decay signatures offer a potential means of experimentally verifying the molecular structure of the Υ(11020) and provide a test of heavy-quark symmetry predictions. The authors acknowledge a dependence on a size parameter, Λ, which was determined by fitting to existing experimental data. This parameter governs the spatial distribution of the constituent mesons within the molecule and influences the calculated decay rates.
Future research could focus on refining the effective Lagrangian and correlation function used in the calculations, as well as exploring the impact of different values for the size parameter on the predicted decay patterns. Further experimental measurements of the Υ(11020)’s decay modes are crucial to validate the theoretical predictions and solidify the understanding of its internal structure.
👉 More information
🗞 Interpretation of Υ(11020)Υ(11020) as an SS-Wave B_1\bar{B}B_1\bar{B}–B_1\bar{B}^*B_1\bar{B}^* Molecular State
🧠 ArXiv: https://arxiv.org/abs/2602.00502