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Zhen-Hua Zhang

Publications and source records attributed to Zhen-Hua Zhang.

At least 19 recordsLinked to original sources
arXiv2026

Comparison of several model averaging methods in nuclear charge radius predictions

The performance of five model averaging methods, including the arithmetic mean (AM), weighted mean (WM), naive Bayesian model averaging (NBMA), principal component analysis (PCA), and power-moderated mean (PMM) methods, in nuclear charge radius predictions is investigated. Five commonly used nuclear charge radius models are adopted as inputs for the averaging procedures. The charge radius differences between the experimental data and the original nuclear models are analyzed and the results after considering the model averaging methods are also discussed. The calculations show that the NBMA method can provide the best root-mean-square (rms) deviation among these five model averaging methods. The PCA method can extract useful physical information and not only helps to interpret the model differences but also offers a feasible way to construct improved empirical models by recombining the principal components. In contrast to the other methods, whose results worsen upon including a new model with a larger rms deviation, the rms deviation of the PCA method remains almost unaffected. The PMM method is capable of integrating the strengths of various nuclear models and delivering reasonable uncertainty estimates not only in known regions but also in unknown ones. This method can automatically adjust data uncertainties to achieve consistency, and it can provide a tool for a smooth transition of the nuclear charge radius prediction from the WM to the AM. The extrapolation ability of these model averaging methods is checked by 66 newly observed data after year 2021. The calculations show that model averaging offers a reliable strategy for nuclear charge radius predictions, combining high accuracy on known data with robust extrapolation to new measurements. The charge radii and the odd-even staggering in calcium isotopes are also discussed.

nucl-th↗
arXiv2026

Full analysis of CP violation induced by the decay angular correlations in four-body cascade decays of heavy hadrons

The violation of the charge-parity (CP) transformation symmetry, which although has been observed in plenty of pure meson decay processes, was only confirmed just very recently by the LHCb collaboration in the four-body decay of the heavy baryon $Λ_b^0$, $Λ_b^0\to p K^- π^+ π^-$, through a comparison of the decay branching ratio with that of the CP-conjugate process. However, the detailed dynamics behind this CP asymmetry is obviously far from clear. In this paper, we propose a formalism for the full analysis of the decay angular correlations in four-body cascade decays of heavy hadrons which can provide more information about the CP violation in these decays. To illustrate this, we apply the decay angular correlation analysis of CP violation to another four-body decay channel that involve baryons, $B^0\to p\bar{p}K^+π^-$, which has also been investigated by the LHCb collaboration with no evidence of CP violation being found. Surprisingly, based on a simple assumption on the statistical errors, and with the event yield extracted inversely from the published data of LHCb, we obtain non-zero CP asymmetries of about $10\%$ corresponding to the decay angular correlations, which are considerably larger than the CPA asymmetries observed in the $Λ_b^0\to p K^- π^+ π^-$ channel. We suggest our experimental colleagues to perform full decay angular correlation analyses of CP violation in four-body decays of heavy hadrons, including the above two decay channels.

hep-ph↗
arXiv2026

CP violation induced by the real part of the interference term in $ρ^0 - ω$ mixing

To circumvent the severe numerical cancellations in the standard integrated CP asymmetry ($A_{CP}$) near the $ω$ mass $m_ω$, we propose a modified CP-violating observable, $A_{CP}^{\Re}$, which explicitly highlights the contribution of the real part of the interference term. Subsequently, we employ the three-body hadronic decay $B^{-} \rightarrow π^{+} π^{-} π^{-}$ within the Perturbative QCD (PQCD) approach as a primary case study to validate this theoretical framework. Furthermore, this method naturally eliminates the smooth, sign-preserving continuum background originating from broad scalar resonances like the $f_0(500)$. This generalized framework provides clean and robust theoretical guidance for recovering localized CP-violation signals that might otherwise be masked by coarse experimental binning at future high-luminosity colliders.

hep-ph↗
arXiv2026

Contributions of interference and non-interference components to CP asymmetries in heavy meson decays

In multi-body decays of heavy mesons, conventional CP asymmetry observables obtained by integrating over the full phase space are insensitive to the higher-order wave expansion contributions in the decay amplitude squared, and consequently fail to retain information on interference effects among different resonances. To overcome this limitation, one can introduce a phase-space partitioning scheme based on the zeros of Legendre polynomials, supplemented by a sign-function weighting procedure. On such a basis, two observables are defined, namely an asymmetry observable $\mathcal{A}_{\pm}^{\mathrm{asy},l}$, and the corresponding CP asymmetry $\mathcal{A}_{\mathrm{CP}}^{\mathrm{asy},l}$. We further separate the observables into interference and non-interference parts and analyze their respective roles. As an application, the decay channel $B^\pm\rightarrowπ^\pmπ^+π^-$ are analyzed in the region near the $ρ^0(1450)$ resonance. Using the LHCb data, the results show that odd-$l$ schemes are particularly effective in isolating interference contributions, while even-$l$ schemes are more sensitive to non-interference terms. This new assignment scheme has the potential to be extended to other decay processes, thus enriching the available physical observables.

hep-ph↗
arXiv2026

Ground-state properties of superheavy $Z=122$ isotopes within the deformed relativistic Hartree-Bogoliubov theory in continuum

The ground-state properties of superheavy $Z = 122$ isotopes are investigated using the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc). Bulk properties, including binding energies, Fermi energies, nucleon separation energies, quadrupole deformations, and root-mean-square radii, are calculated. The results are compared with those obtained from the relativistic continuum Hartree-Bogoliubov (RCHB) theory. By examining the dependence on the angular-momentum cutoff and the effects of triaxial and octupole deformations, a strategy for determining the ground states is suggested. Furthermore, based on an analysis of the Fermi and nucleon separation energies, the proton and neutron drip lines for $Z = 122$ isotopes are determined within both the DRHBc and RCHB frameworks. The possible magic numbers $N=184$, 258, and 350 are also suggested. Finally, the evolution of single-particle levels, deformation, charge and neutron radii as well as average pairing gaps with increasing neutron number, is discussed.

nucl-th↗
arXiv2026

Production of $D_s\bar{D}_s$ and $D\bar{D}$ bound states in the $B$ decays within the Bethe-Salpeter framework

Within the Bethe--Salpeter framework, we investigate the production of possible $D_s\bar{D}_s$ $(X_{s\bar{s}})$ and $D\bar{D}$ $(X_{q\bar{q}})$ bound states in $B$ decays. The bound state properties of the two heavy meson systems are studied in the one-boson-exchange model, and the resulting normalized Bethe--Salpeter wave functions are used to calculate the branching fractions of $B^+\to X_{s\bar s}K^+$ and $B^+\to X_{q\bar q}K^+$. We find that bound state solutions for the $D\bar{D}$ system exist for all the three coupling sets considered, whereas the $D_s\bar{D}_s$ system supports a bound-state solution only in a restricted parameter region. The predicted branching fractions are in the ranges of $1.09\times10^{-5}$--$20.06\times10^{-4}$ for the $D_s\bar{D}_s$ bound state and $1.56\times10^{-6}$--$4.14\times10^{-4}$ for the $D\bar{D}$ bound state. In particular, if $X(3915)$ is interpreted as a predominantly $D_s\bar{D}_s$ bound state, its production

hep-ph↗
arXiv2026

Neutrinoless double-beta decay of the $Δ^-$ resonance

The subprocess $nn\to ppe^-e^-$ is a key ingredient in the interpretation of nuclear neutrinoless double-beta decay. Intermediate $Δ$ resonances may provide additional enhancements to this transition. We take a first step toward a $Δ$-full description of $nn\to ppe^-e^-$ by investigating the neutrinoless double-beta decay $Δ^- \to p e^-e^-$ in the framework of chiral effective field theory. We systematically derive the long-range contribution from light-Majorana-neutrino exchange through loop diagrams and incorporate the short-range part through counterterms required by renormalization. We predict the pion-mass dependence of the decay amplitude in the kinematic configuration with collinear electrons. Furthermore, to facilitate lattice-QCD matching, we calculate the decay amplitude in the degenerate $Δ$-nucleon mass limit and provide the corresponding long-range prediction.

hep-ph↗
arXiv2026

Role of electromagnetic corrections in the $ππ$ distributions of $ψ^\prime \to J/ψππ$

The cusp structure at the $π^+π^-$ threshold in the $π^0π^0$ invariant mass spectrum serves as a sensitive probe for extracting the $S$-wave $ππ$ scattering lengths in processes where an $S$-wave $π^0π^0$ pair is produced in the final states. Within the framework of nonrelativistic effective field theory with coupled channels $π^0π^0$ and $π^+π^-$, we revisit the near-threshold structures in the $π^0π^0$ spectrum of $ψ^\prime \to J/ψππ$. Our analysis incorporates the $ππ$ final-state rescattering, including both strong and Coulomb interactions. It turns out that the cusp near the $π^+π^-$ threshold becomes more prominent when Coulomb interactions are included. The electromagnetic correctionsare found to alter the magnitude of the threshold cusp by about 2%-3%, underscoring the necessity of including these effects in precision determinations of the $ππ$ scattering lengths. The coupled-channel amplitude constructed in this work provides a ready-to-use theoretical framework for experimental analyses of fine structures near $ππ$ thresholds.

hep-ph↗
arXiv2026

The forward-backward asymmetry induced $CP$ asymmetry in ${\overline{B}}^{0}\rightarrow K^{-}π^{+}π^{0}$ in phase space around the resonances ${\overline{K}}^{*}(892)^{0}$ and ${\overline{K}}^{*}_{0}(700)$

The interference between amplitudes corresponding to different intermediate resonances plays an important role in generating large CP asymmetries in phase space in multi-body decays of bottom and charmed mesons. In this paper, we study the CP violation in the decay channel ${\overline{B}}^{0}\rightarrow K^{-}π^{+}π^{0}$ in phase space region where the intermediate resonances $\overline{K}^{*}(892)^{0}$ and ${\overline{K}^{*}_{0}(700)}$ dominate. The Forward-Backward Asymmetry (FBA) and the CP asymmetry induced by FBA (FB-CPA), which are closely related to the interference effects between the two aforementioned resonances, are especially investigated. The non-trivial correlation between FBA and FB-CPA is analyzed. The analysis indicates that the FB-CPAs around the resonance $\overline{K}^{*}(892)^{0}$ can be as large as about 35\%, which can be potentially accessible by Belle and Belle-II collaborations in the near future.

hep-ph↗
arXiv2025

The spectra of $bc\bar{b}\bar{c}$ tetraquark states from a diquark-antidiquark perspective

Within the diquark-antidiquark framework, this study investigates the masses of ground-state tetraquarks composed of heavy charm ($c$) and bottom ($b$) quarks and antiquarks, using the Bethe-Salpeter formalism. We establish the Bethe-Salpeter equations for the fully heavy $bc\bar{b}\bar{c}$ tetraquarks to the leading order in $1/m_Q$ expansion. These equations are subsequently solved numerically under the covariant instantaneous approximation with kernels containing scalar confinement and one-gluon exchange terms. Our results show that the spectra of all possible $S$-wave tetraquark states are above the corresponding two lowest meson decay thresholds via the quark rearrangement. This implies that the ground $bc\bar{b}\bar{c}$ tetraquark states should be broad.

hep-ph↗
arXiv2025

Normalization of partial wave CP asymmetries in three-body decays of heavy hadrons

CP violation in hadronic multi-body decays has been extensively studied, and the experimental breakthrough in the heayy baryon sector was made recently. Partial-Wave CP Asymmetries (PWCPAs) in multi-body decays of heavy hadrons, which although provide us with more interference information, suffer from the normalization problem, as is pointed out in this paper. We propose a novel solution to this problem. We introduce a set of extra factors to rescale the PWCPAs to the proper sizes. Instead of determining the set of factors according to the normalization requirement, we demand that all the PWCPAs have the same statistical errors. In this way, we obtain a set of quasi-normalized PWCPAs, in the sense that they are close to the ideal normalized ones. As an application, we perform an analysis of PWCPAs in the decay channel $B^\pm\toπ^+π^-π^\pm$. We focus on the phase space region where the invariant mass of the $π^+π^-$ pair varies around the vector resonance $ρ^0(1450)$. Based on the data of the LHCb collaboration, the interference patterns among the resonances $ρ^0(1450)$, $f_2(1270)$, and $f_0(1500)$ and their contributions to the quasi-normalized PWCPAs are analyzed. The analysis indicates that the quasi-normalized PWCPAs can avoid potential misleading or distorted results comparing with some other alternatively defined ones.

hep-ph↗
arXiv2025

Constrain the $χ_{cJ}\to D^{(*)}\bar{D}^{(*)}$ effective couplings via the $X(3872)\to π^0χ_{cJ}$ decays

The hidden-charm decays serve as irreplaceable platforms for probing the structures of charmonium-like states, such as $X(3872)$, $Y(4260)$, $Z_c(3900)$, and their heavy-quark-symmetry partners. In the hadronic molecular scenario, these hidden-charm decays are denominated by intermediate meson loops (IMLs), and the couplings of $χ_{cJ}\to D^{(\ast)}\bar{D}^{(\ast)}$ are building blocks of the amplitudes for the pionic and radiative transitions of the charmonium-like states to the $χ_{cJ}$ and $h_c$ states, e.g., $X(3872)\to π^0χ_{cJ},\,ππχ_{cJ},\,γχ_{cJ}$ and $Y(4260)\to π^0 h_c,\,ηh_c$. These couplings can not be extracted from the partial decay widths of the $χ_{cJ}$ directly and only have estimated values from the vector meson dominance (VMD) model. Utilizing the recent precise determination of the pole position and the isospin breaking properties of the $X(3872)$, we give an estimation on the upper bounds of the absolute values of the $χ_{cJ}\to D^{(\ast)}\bar{D}^{(\ast)}$ couplings. Our results show that the VMD model may over estimate the $χ_{cJ}\to D^{(\ast)}\bar{D}^{(\ast)}$ couplings considering the $X(3872)$ as a $D\bar{D}^{*}$ hadronic molecule with a binding energy about tens of keV. These upper limits can be used and tested in other hidden-charm transitions of the charmonium-like states to the $χ_{cJ}$ and $h_c$.

hep-ph↗
arXiv2025

Dihadron Angular Correlations in the $e^+e^-$ Collision

The precision of fixed-order calculations on the dihadron production in electron-positron annihilation is paramount for probing QCD factorization and constraining non-perturbative inputs. This paper investigates the QCD corrections to the angular separation distribution $θ_{12}$ between two observed hadrons, $H_1$ and $H_2$, in the process $e^+e^- \to H_1 H_2 + X$ up to $\mathcal{O}(α_s^2)$, with particular emphasis on the intermediate region $θ_{12} \in (0,π)$. The partonic processes at this accuracy consist of two sorts of contributions, the real-virtual and double-real corrections. Of them, the evaluation of four-body phase space integrals in the latter case is at the core of this study. To address them, we first employ the integration-by-parts (IBP) identities to reduce the number of independent integrals and then apply the differential equations (DE) method to recursively solve the resulting master integrals. In kinematic regions where the invariant mass of the unresolved partons vanishes, IBP coefficients can develop divergences. To this end, we resum higher-order terms in the dimensional regulator for each master integral based on the asymptotic behavior of the canonical DEs. After combining the real and virtual corrections with the counter terms from fragmentation function renormalization, we demonstrate that the pole terms in the final analytic expressions exactly cancel out in all partonic channels, thereby providing a non-trivial validation of collinear factorization at the next-to-leading order (NLO). Eventually, when presenting our analytic expressions of the finite partonic coefficients, we transform the transcendental functions resulting from the DE solutions into classical (poly)logarithmic functions, in order to facilitate the implementation in event generators.

hep-ph↗
arXiv2025

Classification of Coupled-Channel Near-Threshold Structures

Since 2003, plenty of resonant structures have been observed in the heavy quarkonium regime. Many of them are close to the thresholds of a few pairs of heavy hadrons. They are candidates of exotic hadrons and have attracted immense attentions. Based on a coupled-channel nonrelativistic effective field theory, we classify the near-threshold structures of a symmetry-related two-channel system by studying the evolution of the scattering amplitude line shapes and pole positions with the variation of the single-channel scattering length and channel coupling strength. We show that the evolution of the scattering amplitude line shapes can be understood from the pole trajectories in the complex energy plane, and the pole evolution can be traced back to the renormalization group fixed points. We provide a dictionary of correspondence between the evolution of line shapes and pole trajectories along with varying interaction and channel coupling strengths, which can be used to understand the experimental observations of the near-threshold structures.

hep-ph↗
arXiv2025

Coupled-channel analysis of the near-threshold $e^+e^-\to N\bar{N}$ cross sections

The possible existence of nucleon-antinucleon bound states has been studied for decades. We investigate the $e^+e^-\to p\bar{p}$ and $e^+e^-\to n\bar{n}$ cross sections in the nonrelativistic effective field theory framework. The proton-antiproton and neutron-antineutron coupled-channel final state interactions are considered and found responsible for near-threshold enhancements. Both the proton-neutron mass difference and the Coulomb interaction between $p$ and $\bar{p}$ are considered, and the $N\bar{N}$ strong interactions are taken into account through a short-distance optical potential. By fitting the low energy constants in the amplitudes to the data for the near-threshold $e^+e^-\to N\bar{N}$ cross sections from the BESIII and SND Collaborations, a $N\bar{N}$ quasi-bound state is found just above the $p\bar{p}$ threshold, and another $N\bar{N}$ pole is found on the unphysical Riemann sheet, farther away from the threshold. The constructed coupled-channel amplitude with Coulomb effects also offers a framework that can be used directly in experimental analyses on fine structures near the $N\bar{N}$ thresholds.

hep-ph↗
arXiv2024

Dispersive analysis of the isospin breaking in the $X(3872)~\to~J/ψπ^+π^-$ and $X(3872)~\to~J/ψπ^+π^0π^-$ decays

We analyze the latest LHCb data on the $π^+π^-$ spectrum in the isospin-violating $X(3872)\to J/ψπ^+π^-$ decay, based on dispersion theory to deal with the $ππ$ final state interactions. Additionally, the isospin breaking effects are properly introduced, allowing for a reliable and accurate extraction of the ratio, $R_X$, between the $X(3872)$ couplings to the $J/ψρ$ and $J/ψω$ channels from the data. We find very good agreement with the LHCb data for the whole range of the $π^+π^-$ invariant mass, and $R_X$ is determined to be {$0.26\pm 0.03$}. Using this value, we make predictions for the $π^+π^0π^-$ mass distribution in the $X(3872)\to J/ψπ^+π^0π^-$ process, which is currently accessible by the BESIII Collaboration, and update a prediction for the pole positions of the isovector partner states of the $X(3872)$, $W_{c1}$, with $I(J^{PC})=1(1^{++})$.

hep-ph↗
arXiv2024

Probing the soft rescattering parameters in $B$ decays involving a scalar meson with QCD factorization

In this work, the soft rescattering parameters in the $B^\pm\rightarrow π^\pmπ^+π^-$ and $B^\pm\rightarrow K^\pmπ^+π^-$ decays with the light scalar meson $f_0(500)$ as the intermediate resonance are studied within the QCD factorization. Considering the interference effect between $ρ(770)^0$ and $f_0(500)$, we utilize the experimentally more direct event yields for fitting and get the soft rescattering parameters $|ρ_k^{SP}|=3.29\pm1.01$ and $|ρ_k^{PS}|=2.33\pm0.73$ in $B\rightarrow PS$ and $B\rightarrow SP$ decays ($P$ and $S$ denote pseudoscalar and scalar mesons, respectively), respectively. We also study the branching ratios and $CP$ asymmetries in the decay modes involving other scalar mesons, including $f_0(980)$, $a_0(980)$, $a_0(1450)$ and $K_0^*(1430)$, to test the rationality of the values of $|ρ_k^{SP}|$ and $|ρ_k^{PS}|$. Meanwhile, the wealth of experimental data facilitate the examination of the forward-backward asymmetry induced $CP$ asymmetries (FB-CPAs), and the localized $CP$ asymmetries (LACPs). We investigate these asymmetries resulting from the interference between $ρ(770)^0$ and $f_0(500)$ for $B^\pm\rightarrow π^\pmπ^+π^-$ and $B^\pm\rightarrow K^\pmπ^+π^-$ decays when the invariant mass of $π^+π^-$ locates in the low-energy region $0.445\mathrm{GeV}<m_{ππ}<0.795\mathrm{GeV}$. Our theoretical results of FB-CPAs and LACPs align with the experimental findings. We propose that the interference between $ρ(770)^0$ and $f_0(500)$ can be extended to other beauty and charmed mesons decays.

hep-ph↗