arXiv subjects

Zi-Yue Bai

Publications and source records attributed to Zi-Yue Bai.

14 recordsLinked to original sources

arXiv2026

Unquenched Charmonium and Beyond

The year 2024 marked the 50th anniversary of the discovery of the $J/ψ$ particle, which unveiled the charm quark and the charmonium spectrum, instigating the "November Revolution" in particle physics. This discovery catalyzed the development of quenched potential models, most notably the Cornell model, which provided a foundational quantitative description of the hadronic spectrum. However, the landscape of hadron spectroscopy has been profoundly transformed since the turn of the 21st century with the observation of numerous charmonium-like states, such as $X(3872)$, which exhibit properties starkly at odds with quenched model predictions. These discrepancies, exemplified by the "$X(3872)$ low-mass puzzle" and the "$Y$ problem" associated with vector states like $Y(4260)$, underscore the critical limitations of the quenched approximation and signal the necessity for a new theoretical paradigm. This review synthesizes recent advances in hadronic spectroscopy, arguing that the unquenched picture, which incorporates coupled-channel effects such as hadronic loops, is essential for a unified description of these new states and associated anomalies. We demonstrate how unquenched effects provide compelling solutions to long-standing puzzles in charmonium decays (e.g., the "$ρπ$ puzzle" and anomalous dipion transitions), predict and explain the existence of exotic charged states like $Z_c(3900)$ and $Z_b(10610)$ via mechanisms such as Initial Single Pion Emission, and offer a framework for understanding interactions between charmonia and with nucleons. Furthermore, we emphasize the universality of unquenched effects, extending their application to bottomonium and light-flavor sectors. As experimental precision continues to improve, we advocate for the systematic development of unquenched hadronic spectroscopy.

hep-ph↗

arXiv2026

Production of high-orbital kaon excited states in the $K^{-}p$ reaction

In this work, a systematic investigation of the production of high-orbital-excitation kaons in $K^{-}p$ reactions is carried out within an effective Lagrangian approach. The relevant $t$-channel processes are constructed, and the model is calibrated using a single adjustable parameter determined from existing experimental data. With this parameter, the measured production cross sections for the $K_3^*(1780)$, $K_2(1820)$, $K_2(1770)$ and $K_4^*(2045)$ states are successfully reproduced. Employing the same framework, the production cross sections for other high-orbital kaons are predicted. The results indicate that these states possess sizable cross sections and exhibit characteristically forward-peaked angular distributions, which is a typical feature of $t$-channel exchange, highlighting their great potential for observation in future experiments.

hep-ph↗

arXiv2026

Production of high-spin $ω_J/ρ_J$ ($J=2,3,4,5$) mesons in $π^{-}p$ reactions

In this work, we perform a comprehensive investigation of the production of high-spin $ω_J$ and $ρ_J$ mesons ($J=2,3,4,5$) in $π^- p$ reactions using an effective Lagrangian approach. By constructing the relevant $t$-channel processes and calibrating the model with a single adjustable parameter fitted to existing data, we successfully reproduce the measured total and differential cross sections for the $J=3$ states $ω_3(1670)$ and $ρ_3(1690)$. Within the same framework, we predict the production cross sections for their lower- and higher-spin partners: $ω_2(1975)$, $ρ_2(1940)$, $ω_4(2250)$, $ρ_4(2230)$, $ω_5(2350)$, and $ρ_5(2350)$. Our results show that these states exhibit measurable cross sections with characteristically forward-peaked angular distributions, underscoring their strong potential for observation in future $πp$ meson-beam experiments.

hep-ph↗

arXiv2025

Exploring the role of higher $ω$ meson states in the $e^+ e^-\rightarrow b_1(1235) π$ process

The properties of light vector mesons near 2.2 GeV remain poorly understood, impeding progress in mapping the higher-lying hadronic spectrum. Utilizing the newly released BESIII data on the Born cross sections for the process of $e^+ e^- \rightarrow b_1(1235) π$, we conduct a combined analysis incorporating theoretical predictions for the mass spectrum and decay properties of $ω$-meson family. Our fit demonstrates that the enhancement structure near 2.2 GeV originates not from a single resonance, but from the significant interference between the $ω(4S)$ and $ω(3D)$ states, which have comparable contributions. This interpretation resolves the apparent discrepancy in the resonance parameters and yields values consistent with theoretical expectations. Our work provides a key interpretation of the vector enhancement structure and establishes a vital framework for identifying higher radial and orbital excitations in the $ω$ meson family, thereby advancing the mapping of the light-hadron spectrum.

hep-ph↗

arXiv2025

Decoding the role of $ρ$ mesonic states for elucidating the $e^+e^-\to a_2(1320)π$ data and other reactions

Recently, the BESIII Collaboration observed a $ρ$-like structure $Y(2044)$ in $e^+e^-\to a_2(1320)π$, suggesting that $Y(2044)$ may be a candidate of vector meson $ρ(2D)$ by comparing resonance parameters. However, the theoretical prediction for the combined branching ratio $Γ_{e^+e^-}\mathcal{B}_{a_2(1320)π}$ for the pure $ρ(2D)$ state is about two orders of magnitude smaller than the experimental value. To resolve this discrepancy and decipher the nature of $Y(2044)$, this work propose an $S$-$D$ mixing scheme to reanalyze the cross section of $e^+e^-\to a_2(1320)π$, and find that the aforementioned branching ratio discrepancy can be resolved. Our results show that the $Y(2044)$ structure can be reproduced by introducing four theoretically predicted $S$-$D$ mixing $ρ$ meson states $ρ_{3S-2D}^{\prime}$, $ρ_{3S-2D}^{\prime\prime}$, $ρ_{4S-3D}^{\prime}$, and $ρ_{4S-3D}^{\prime\prime}$ as intermediate resonances, in which dominant contribution arises from $ρ_{3S-2D}^{\prime\prime}$ and their inference effect is also significant. Furthermore, we reanalyzed five additional isospin vector processes $e^+e^-\to ωπ^0$, $e^+e^-\to f_1(1285)π^+π^-$, $e^+e^-\to π^+π^-$, $e^+e^-\to ρη$, and $e^+e^-\to η^{\prime} π^+π^-$ based on the same $S$-$D$ mixing framework, and simultaneously reproduced their experimental cross section data. This work provides a unified framework to elucidate all observed $ρ$-like structures near 2 GeV in the $e^+e^-$ annihilation processes, and suggests that the $S$-$D$ mixing effect may be crucial for understanding the mass spectrum and decay behaviors of the higher $ρ$ meson states.

hep-ph↗

arXiv2025

Coupled-channel study of $4S$-$3D$ mixing dynamics in $ψ(4220)$ and $ψ(4380)$

Among charmoniumlike $XYZ$ states, the $ψ(4220)$ and $ψ(4380)$ states have emerged as key candidates for exploring the charmonium spectrum. In this work, we propose a $4S$-$3D$ charmonium mixing scheme for the $ψ(4220)$ and $ψ(4380)$, induced by coupled-channel effects. By constructing a coupled-channel model, we identify the dynamical mechanism responsible for the large mixing angle observed in previous studies, which cannot be explained by conventional potential models alone. Our analysis reveals that the $DD_1$ channel significantly influences the lower state ($ψ(4220)$), while the $D^*D_1$ channel primarily affects the higher state ($ψ(4380)$). Furthermore, we investigate the two-body Okubo-Zweig-Iizuka (OZI)-allowed strong decay behaviors of these states, providing insights into their total widths. This study not only supports the $4S$-$3D$ mixing scheme but also offers a deeper understanding of the role of coupled channels in shaping the charmonium spectrum above 4 GeV. Our results align with experimental observations and provide a framework for interpreting future data on charmonium states.

hep-ph↗

arXiv2025

Non-$D\bar{D}$ Decays into Light Meson Pairs of the $D$-Wave Charmonium $ψ_3(3842)$

As a $D$-wave partner of $ψ(3770)$ identified by the LHCb Collaboration, $ψ_3(3842)$ lies between the $D\bar{D}$ and $D\bar{D^*}$ thresholds. Its non-$D\bar{D}$ decay channels have attracted considerable interest. In this study, we investigate these allowed non-$D\bar{D}$ decays of $ψ_3(3842)$ into $PP$, $PV$, and $VV$ final states using the hadronic loop mechanism, where $P$ and $V$ represent light pseudoscalar and vector mesons, respectively. Our results suggest that these non-$D\bar{D}$ decays of $ψ_3(3842)$ can be significant, with contributions primarily driven by hadronic loops. Notably, the $ρπ$ channel stands out as the main non-$D\bar{D}$ decay mode, while non-$D\bar{D}$ decay channels involving strange mesons are also sizable. These predictions could be tested in future experiments such as those at LHCb and BESIII.

hep-ph↗

arXiv2025

Role of $4S$-$3D$ mixing in explaining the $ω$-like $Y(2119)$ observed in $e^+e^-\toρπ$ and $ρ(1450)π$

The BESIII Collaboration has recently reported a new resonance structure in the cross-section analyses of the $e^+e^- \to ρπ$ and $e^+e^- \to ρ(1450)π$ processes, displaying characteristics akin to an $ω$-meson. However, its measured mass, $M = 2119 \pm 11 \pm 15 \, \text{MeV}$, significantly deviates from the predictions of the unquenched relativized potential model for conventional $ω$ vector meson spectroscopy. To address this discrepancy, we propose a $4S$-$3D$ mixing scheme and investigate the corresponding decay properties within this framework. Our analysis demonstrates that the mixed state $ω_{4S\text{-}3D}^\prime$ exhibits excellent agreement with the observed resonance, not only in mass and width but also in the products of its dielectron width and branching ratios, $Γ_{e^+e^-}^{\mathcal{R}}\times\mathcal{B}_{\mathcal{R}\toρπ}$ and $Γ_{e^+e^-}^{\mathcal{R}}\times\mathcal{B}_{\mathcal{R}\toρ(1450)π\toπ^+π^-π^0}$. The determined mixing angle, $θ= -\left(31.1^{+2.1}_{-3.1}\right)\degree$, strongly supports the interpretation of this structure as the $ω_{4S\text{-}3D}^\prime$ state. Furthermore, we predict dominant decay channels for $ω_{4S\text{-}3D}^\prime$ and its partner state $ω_{4S\text{-}3D}^{\prime\prime}$. These predictions, together with the proposed mixing mechanism, provide crucial guidance for future experimental studies aimed at probing this structure and rigorously testing the $4S$-$3D$ mixing hypothesis.

hep-ph↗

arXiv2025

Reevaluating the $ψ(4160)$ Resonance Parameter Using $B^+\to K^+μ^+μ^-$ Data in the Context of Unquenched Charmonium Spectroscopy

A puzzling phenomenon, where the measured mass of the $ψ(4160)$ is pushed higher, presents a challenge to current theoretical models of hadron spectroscopy. This study suggests that the issue arises from analyses based on the outdated quenched charmonium spectrum. In the past two decades, the discovery of new hadronic states has emphasized the importance of the unquenched effect. Under the unquenched picture, six vector charmonium states-$ψ(4040)$, $ψ(4160)$, $ψ(4220)$, $ψ(4380)$, $ψ(4415)$, and $ψ(4500)$-are identified in the $4 \sim 4.5$ GeV range, contrasting with the three states predicted in the quenched model. We reevaluate the resonance parameters of the $ψ(4160)$ using the di-muon invariant mass spectrum of $B^+ \to K^+ μ^+ μ^-$ and unquenched charmonium spectroscopy. Our analysis finds the $ψ(4160)$ mass at $4145.76 \pm 4.48$ MeV, indicating previous overestimations. This conclusion is supported by analyzing $e^+e^- \to D_s \bar{D}_s^*$. Our findings have significant implications for both hadron spectroscopy and search for new physics signals by $R_K$.

hep-ph↗

arXiv2024

How higher charmonia shape the puzzling data of the $e^+e^-\to ηJ/ψ$ cross section

Recently, the BESIII collaboration performed a precise measurement of the $e^+e^-\to ηJ/ψ$ cross section. It is puzzling that the resonance parameters of the reported $Y(4230)$ show a substantial divergence from the previously measured results in both the open-charmed and hidden-charmed decay channels, and the line shape asymmetry of the data approaching 4.2 GeV also suggests that it might be difficult to characterize the details of the structure around 4.2 GeV by a single resonance. This has motivated our great curiosity about how the charmonium states are distributed in the measured energy range and how they shape the puzzling data of the $e^+e^-\to ηJ/ψ$ cross section. In this work, we use five theoretically constructed charmonia in the range of $4.0\rm{-}4.5$ $\text{GeV}$, i.e., $ψ(4040)$, $ψ(4160)$, $ψ(4220)$, $ψ(4380)$, and $ψ(4415)$, to apply a combined fit to the data, in which their calculated decay ratios into $ηJ/ψ$ via hadronic loop mechanism are taken as input. The fit results can reproduce the measured cross section data well, especially for the subtle line shape around 4.2 GeV, showing that the structure around 4.2 GeV is possible from the contribution of both $ψ(4160)$ and $ψ(4220)$.

hep-ph↗

arXiv2023

Higher strangeonium decays into light flavor baryon pairs like $Λ\barΛ$, $Σ\barΣ$, and $Ξ\barΞ$

In this work, we investigate the decay behaviors of several higher strangeonia into $Λ\barΛ$ through a hadronic loop mechanism, enabling us to predict some physical observables, including the branching ratios. Furthermore, we assess the reliability of our research by successfully reproducing experimental data related to the cross section of $e^+e^-\toΛ\barΛ$ interactions. In this context, we account for the contributions arising from higher strangeonia, specifically $ϕ(4S)$ and $ϕ(3D)$. Additionally, we extend this study to encompass higher strangeonia decays into other light flavor baryon pairs, such as $Σ\barΣ$ and $Ξ\barΞ$. By employing the same mechanism, we aim to gain valuable insights into the decay processes involving these particles. By conducting this investigation, we hope to shed light on the intricate decay mechanisms of higher strangeonia and their interactions with various baryons pairs.

hep-ph↗

arXiv2022

Investigating the $\mathbf{Υ(10753)\to Υ(1^3D_J)η}$ transitions

In this work, we investigate the $Υ(10753)\toΥ(1^3D_J)η$ ($J=1,2,3$) processes, where the $Υ(10753)$ is assigned as a conventional bottomonium under the $4S$-$3D$ mixing scheme. Our result shows that the concerned processes have considerable branching ratios, {\it i.e.}, branching ratios $\mathcal{B}[Υ(10753)\toΥ(1^3D_{1})η]$ and $\mathcal{B}[Υ(10753)\toΥ(1^3D_{2})η]$ can reach up to the order of magnitude of $10^{-4}-10^{-3}$, while $\mathcal{B}[Υ(10753)\toΥ(1^3D_{3})η]$ is around $10^{-6}-10^{-5}$. With the running of Belle II, it is a good opportunity for finding out the concerned hidden-bottom hadronic decays.

hep-ph↗

arXiv2022

$\mathbf{Υ(10753)\toΥ(nS)π^+π^-}$ decays induced by hadronic loop mechanism

In this work, we investigate the $Υ(10753)\toΥ(nS)π^+π^-$ ($n=1,2,3$) processes by considering the hadronic loop mechanism, where $Υ(10753)$ is assigned to a conventional bottomonium in the $4S$-$3D$ mixing scheme. Our results of the concerned processes own considerable branching ratios, which can reach up to the order of magnitude of $10^{-4}-10^{-3}$. We should indicate that the measured $Γ_{e^+e^-}\times\mathcal{B}[Υ(10753)\toΥ(nS)π^+π^-]$ values given by Belle can be reproduced well. This fact supports the former bottomonium assignment to the $Υ(10753)$ in the $4S$-$3D$ mixing scheme. Obviously, it is a good opportunity for the ongoing Belle II experiment if the predicted result in this work can be tested further.

hep-ph↗

arXiv2021

Hidden-bottom hadronic decays of $Υ(10753)$ with a $η^{(\prime)}$ or $ω$ emission

In this work, we propose the $4S$-$3D$ mixing scheme to assign the $Υ(10753)$ into the conventional bottomonium family. Under this interpretation, we further study its hidden-bottom hadronic decays with a $η^{(\prime)}$ or $ω$ emission, which include $Υ(10753)\toΥ(1S)η^{(\prime)}$, $Υ(10753)\to h_{b}(1P)η$ and $Υ(10753)\toχ_{bJ}ω$ ($J$=0,1,2) processes. Since the $Υ(10753)$ is above the $B\bar{B}$ threshold, the coupled-channel effect cannot be ignored, thus, when calculating partial decay widths of these $Υ(10753)$ hidden-bottom decays, we apply the hadronic loop mechanism. Our result shows that these discussed decay processes own considerable branching fractions with the order of magnitude of $10^{-4}\sim 10^{-3}$, which can be accessible at Belle II and other future experiments.

hep-ph↗