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Zhi-Gang Wang

Publications and source records attributed to Zhi-Gang Wang.

At least 19 recordsLinked to original sources

The semileptonic decays of $Ω_{b}^{*}$, $Σ_{b}^{*}$ and $Ξ_{b}^{\prime*}$ baryons

In this article, we employ the QCD sum rules basing on three-point correlation function to systematically analyze the transition form factors for the semileptonic decays of the spin \(\frac{3}{2}^{+}\) bottom baryons (\(Ω_{b}^{*}\), \(Σ_{b}^{*}\), and \(Ξ_{b}^{\prime *}\)) to their corresponding spin \(\frac{1}{2}^{+}\) charmed partners. On the phenomenological side, we eliminate the contaminations of the baryons with negative parity and those with lower spin states. The operator product expansion is carried out up to dimension-six condensates, including the perturbative part, quark condensate \(\langle \bar{q} q\rangle\), gluon condensate \(\langle g_{s}^{2}GG\rangle\), mixed condensate \(\langle \bar{q} g_{s}σGq\rangle\), and four-quark condensates \(\langle \bar{q} q\rangle^{2}\) and \(g_{s}^{2}\langle \bar{q} q\rangle^{2}\). The form factors are evaluated in the space-like region and then are fitted into the time-like physical region via a $z$-series expansion approach. Finally, the semileptonic decay widths for $Ω_{b}^{*}$, $Σ_{b}^{*}$ and $Ξ_{b}^{\prime*}$ baryons are calculated with our predicted form factors, and various polarization observables are also predicted. The predicted results in this work are compared with those predicted by other collaborations, and are expected to be useful for studying the properties of these singly heavy baryons.

hep-ph↗

A counterexample to an open problem of Dorff

The classical Pólya-Schoenberg conjecture, proved by Ruscheweyh-Sheil-Small, asserts that the convolution of two normalized convex univalent functions is again convex. This property fails to carry over to planar harmonic mappings. In 2001, Dorff posed the open problem whether the self-convolution of a normalized convex harmonic mapping with bounded image must remain in the same class. We construct a normalized sense-preserving harmonic diffeomorphism that maps the unit disk onto an ellipse; its self-convolution has vanishing Jacobian at some interior point of the unit disk, which provides a negative answer to Dorff's open problem.

math.CV↗

Analysis of the $X(2370)$ as a glueball based on rigorous current-field duality

In this work, we take the $X(2370)$ with $J^{PC}=0^{-+}$ as a glueball consists of three valence gluons, and construct a six-quark current based on rigorous current-field duality to obtain the glueball-quark Lagrangian. Then we perform Fierz transformation to bosonize the quark current into a series of three pseudoscalar mesons. At last, we obtain ratios among the partial decay widths of the glueball to three pseudoscalar mesons in a model-independent way, which are compatible with the experimental data from the BESIII Collaboration and support assigning the $X(2370)$ as a glueball.

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Analysis of the two-body strong decays of the hidden-charm pentaquark states in QCD sum rules

In the present work, we study the two-body strong decays of the hidden-charm pentaquark states with the quark content $uudc\bar c$ and the quantum numbers $I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$ in the framework of the three-point QCD sum rules. The initial pentaquark states are described by four local diquark-diquark-antiquark type interpolating currents with definite isospin. We construct the three-point correlation functions for the decay channels $P_c\to η_c p$, $J/ψp$, $Λ_c\bar D$, $Λ_c\bar D^{*}$ and $Σ_c\bar D$, and derive the corresponding QCD sum rules for the strong coupling constants. At the hadron side, the correlation functions are expressed in terms of the hadron masses, pole residues, decay constants and strong coupling constants. At the QCD side, they are calculated by carrying out the operator product expansion with the full quark propagators, where the vacuum condensates up to dimension 10 are taken into account. After matching the two representations and performing the double Borel transformations, we extract the strong coupling constants from the selected Lorentz structures. With the obtained coupling constants, we evaluate the partial decay widths and discuss the possible assignments of the corresponding pentaquark states. The numerical results indicate that two of the compact hidden-charm pentaquark states can be related to the $P_c(4312)$ and $P_c(4457)$, respectively, while the other two lower-mass states may be regarded as possible hidden-charm pentaquark candidates to be searched for in future experiments. The present results may be useful for identifying the hidden-charm pentaquark states in future experiments.

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Analysis of the hidden-charm pentaquark candidates in the $J/ψΩ$ mass spectrum via the QCD sum rules

We explore the diquark-diquark-antiquark type $sssc\bar{c}$ pentaquark states with the isospin-spin-parity $IJ^{P}=0{\frac{1}{2}}^-$, $0{\frac{3}{2}}^-$ and $0{\frac{5}{2}}^-$ via the QCD sum rules in details and obtain the ground state mass spectrum. And we suggest to hunt for these exotic states in the exclusive decay $Ω_b^- \to P_{csss}^-ϕ\to J/ψΩ^- ϕ$. Observations of the $P_{csss}$ states would shed light on the nature of exotic states and provide an excellent opportunity to distinguish the diquark-diquark-antiquark type pentaquark states from meson-baryon type molecular states.

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Analysis of the hidden-charm pentaquark candidates in the $J/ψΞ^*$ mass spectrum via the QCD sum rules

In this work, we explore the diquark-diquark-antiquark type decuplet hidden-charm pentaquark states with the symbolic valence structure $qssc\bar{c}$ via the QCD sum rules extensively, and achieve the spectroscopy of the lowest decuplet $qssc\bar{c}$ pentaquark states with the quantum numbers $IJ^{P}=\frac{1}{2}{\frac{1}{2}}^-$, $\frac{1}{2}{\frac{3}{2}}^-$ and $\frac{1}{2}{\frac{5}{2}}^-$, and suggest to explore these exotic states in the exclusive processes $Ξ_b^{\prime0} \to P_{css}^0\,ϕ\to J/ψΞ^{*0} ϕ$ and $Ω_b^{-}\to P_{css}^-\, \bar{K}^0 \to J/ψΞ^{*-}\, \bar{K}^0$. As a byproduct, we can re-testify classifications of the light baryons by investigating the hidden-charm pentaquark decays.

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The $Λ_cΣ_c$ dibaryon and $\barΛ_cΣ_c\pm \barΣ_cΛ_c$ baryonium states via the QCD sum rules

In the present work, we study the $Λ_cΣ_c$ dibaryon and $\barΛ_cΣ_c\pm \barΣ_cΛ_c$ baryonium states via the QCD sum rules. We construct four (eight) currents with definite $J^P$ ($J^{PC}$) to interpolate the dibaryon (baryonium) states and obtain twelve QCD sum rules. For the dibaryon states, the state with the $J^P=1^+$ lies below the $Λ_cΣ_c$ threshold, and is a molecule candidate. For the baryonium states, the states with the $J^P=0^{-\pm}$ and $1^{-\pm}$ lie below the $\barΛ_cΣ_c$ threshold, and are four molecule candidates. The present predictions can be confronted to the experimental data in the future and make contributions to the exotic spectroscopy.

hep-ph↗

Low-lying singly heavy baryon states based on the rigorous calculation with the relativized quark model

In this work, the low-lying $\mathbf{6}_{F}$ singly heavy baryon states with positive-parity are studied in detail in the framework of the relativized quark model by using the improved calculation scheme which has successfully explained the fine structure of the low-lying negative-parity singly heavy baryons. The complete mass spectra of all the singly heavy baryon families obtained in the same framework and calculation scheme are systematically analyzed. The baryon states marked with (mass)$J^{P}$ are obtained by considering the mixing effect rigorously. It is found that the mixing effect in the singly heavy baryons depends on the flavor symmetry of the two light quarks and the baryon parity. The results show that the high-precision calculation can reproduce most of the data perfectly, and the statistical error between the calculated masses and the experimental data is only 6.96 MeV. This confirms the reliability of the improved calculation scheme. The rigorous calculation achieved by the two-step GEM enables us to analyze the detailed behavior of the various strong interaction components within the baryons with a high-precision and discover the truth of the ``soft QCD''. The large amount of data obtained in this work serves as the reliable references for related experimental and theoretical researches.

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Analysis of the hidden-charm pentaquark candidates in the $J/ψΣ^*$ mass spectrum via the QCD sum rules

In this work, we study the diquark-diquark-antiquark type $uusc\bar{c}$ pentaquark states in the light-flavor $\mathbf{10}$ representation via the QCD sum rules in details. We exhaust the lowest five-quark configurations and obtain the spectroscopy of the $uusc\bar{c}$ pentaquark states with the quantum numbers $IJ^{P}=1{\frac{1}{2}}^-$, $1{\frac{3}{2}}^-$, $1{\frac{5}{2}}^-$, and suggest to investigate them in the decay chain $Σ_b^+\to P_{cs}^+\,ϕ\to J/ψΣ^{*+}\, ϕ$ experimentally.

hep-ph↗

The semileptonic decays of $\mathcal{B}_{Q_{1}Q_{2}}(\frac{1}{2}^{+})\rightarrow\mathcal{B}_{Q_{1}}^{*}(\frac{3}{2}^{+})$ in QCD sum rules

In the framework of QCD sum rules, we systematically analyze the weak transition process $\mathcal{B}_{Q_{1}Q_{2}}(\frac{1}{2}^{+})\rightarrow\mathcal{B}_{Q_{1}}^{*}(\frac{3}{2}^{+})$. When doing the operator product expansion in the QCD side, we consider the contributions of perturbative part and vacuum condensate terms up to dimension 6. In the phenomenological side, we eliminate the interferences of the low spin states and negative parity states by employing 16 different dirac structures. As an application, these form factors are finally used to analyze the semileptonic decays of $\mathcal{B}_{Q_{1}Q_{2}}(\frac{1}{2}^{+})\rightarrow\mathcal{B}_{Q_{1}}^{*}(\frac{3}{2}^{+})lν$, where these decays are driven by the transition processes $c\rightarrow d/s+l^{+}+ν_{l}$ and $b\rightarrow u+l^{-}+\overlineν_{l}$. The predicted physical quantities include not only the partial widths, ratios of $Γ_{L}/Γ_{T}$ and the branching fractions, but also some observables such as the forward-backward asymmetry parameter $A_{FB}^{l}$ of lepton, the $P_z^{F}$ component of the polarization vector for daughter baryon and the longitudinal polarization of the lepton $P_z^{l}$. We hope all of these theoretical predictions about the weak decays will be helpful for studying the properties of doubly heavy baryons in experiments in the future.

hep-ph↗

Could $\barΛ_c$ and $Λ_c$ form bound hadronic molecule with explicit $P-wave$ ?

In this article, the explicit $P-wave$ of the $\barΛ_cΛ_c$ dibaryon states with the $J^{PC}=0^{-\pm}$ and $1^{-\pm}$ are studied via twelve interpolated currents. Results show that the positive and negative charge conjugations for the studied states do not have too much difference, the contribution of the gluon from covariant derivative of the current with $P-wave$ could be neglected. The numerical results of the masses of the $P-wave$ $\barΛ_cΛ_c$ are high above the threshold of the two $\barΛ_c$ and $Λ_c$ baryon constituents, $\barΛ_c$ and $Λ_c$ are unlikely to form the bound molecules with explicit $P-wave$ . Pole residues of the related states are also calculated.

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Systematic study of the strong decays of the $P_c$ states and their possible isospin cousins via the QCD sum rules

In the present work, the strong decays of the discovered $P_c(4380)$, $P_c(4440)$, $P_c(4457)$ and their possible isospin cousins are systematically studied via the assignment that they are the meson-baryon molecular states. In detail, the strong decay constants, partial decay widths of their decay channels are calculated under the framework of QCD sum rules. The decay withes of the discovered $P_c(4380)$, $P_c(4440)$ and $P_c(4457)$ are in good agreement with the experiments. The predictions of the decays of these three related possible isospin cousins are presented which would shed light for their findings in experiment, in return, this may testify the assignments of the discovered $P_c$ states.

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Analysis of the semileptonic decays $Σ_b\toΣ_cl\barν_l$, $Ξ'_b\toΞ'_cl\barν_l$ and $Ω_b\toΩ_cl\barν_l$ in QCD sum rules

In this article, the electroweak transition form factors of $Σ_b\toΣ_c$, $Ξ'_b\toΞ'_c$ and $Ω_b\toΩ_c$ are analyzed within the framework of three-point QCD sum rules. In phenomenological side, all possible couplings of interpolating current to hadronic states are considered, and the Dirac structure dependence on the form factors is systematically eliminated. In QCD side, our calculation incorporates both the perturbative part and the contributions from vacuum condensates up to dimension 8. This systematic inclusion of higher-dimensional terms accounts for a broader set of Feynman diagrams, thereby enhancing the comprehensiveness and reliability of the operator product expansion. Using the obtained form factors, we study the partial widths of semileptonic decays $Σ_b\toΣ_cl\barν_l$, $Ξ'_b\toΞ'_cl\barν_l$ and $Ω_b\toΩ_cl\barν_l$ ($l=e$, $μ$ and $τ$). The results indicate that these decay widths approximately satisfy SU(3) flavor symmetry. Next, we calculate the branching ratios for the decay process $Ω_b\toΩ_cl\barν_l$ and compare them with the results from other collaborations. Furthermore, the lepton universality ratios and some asymmetry parameters of these decay processes are also analyzed, which provide information for the study of new physics. We hope that these results will serve as a useful reference for future theoretical and experimental studies of weak decays involving heavy flavor baryons.

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Analysis of the hidden-charm pentaquark candidates in the $J/ψΣ$ mass spectrum via the QCD sum rules

In this work, we adopt the diquark model, construct the diquark-diquark-antiquark type currents with the light quarks $uus$ in two octets, and study the $uusc\bar{c}$ pentaquark states in the framework of the QCD sum rules systematically. We obtain the mass spectrum of the hidden-charm-singly-strange pentaquark states with the quantum numbers $IJ^{P}=1{\frac{1}{2}}^-$, $1{\frac{3}{2}}^-$ and $1{\frac{5}{2}}^-$. And we can search for those $P_{cs}$ states in the processes $Σ_b^+\to P_{cs}^+ϕ\to J/ψΣ^+ \,ϕ$ and $Ξ_b^0\to P_{cs}^+ K^- \to J/ψΣ^+\, K^-$.

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Spin-dependent interactions and fine structure in the negative-parity singly heavy baryons

In order to meet the high-precision measurement of the current baryon spectroscopy, for the first time, we rigorously analyze the spin-dependent interactions and the fine structure of the negative-parity singly heavy baryons in the relativized quark model, which was previously unfeasible in the three-quark system. This gains access to the exploration of the strong interactions dominated by the non-perturbative QCD, and reveals how the various forms of strong interactions in a baryon compete with each other, affect the evolution of the energy levels, cause the energy level splitting and contribute to the mixing effect responsible for the formation of the fine structures. It is shown that the rigorous calculation can perfectly reproduce the data, the averaged deviation between the calculated and experimental energy levels is less than 5 MeV for the negative-parity singly heavy baryons. Therefore, the theoretical precision has reached the experimental high precision. This confirms the reliability of the calculation and also helps make reasonable assignments for the observed negative-parity baryons. The large amount of data obtained by the rigorous calculations contains a wealth of interaction information and is helpful for both of the theoretical and experimental studies. The key to the rigorous calculation in this work is the proposal of a new method, namely the two-step Gaussian expansion method. This new method not only overcomes the long-standing unresolved problem in the relativized quark model, but also provides an effective approach for the high-precision calculation of other few-body systems such as the compact tetraquarks and pentaquarks, especially for the treatment of spin-orbit interactions and tensor interactions which actually appear ubiquitously in all of quantum many-body systems.

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Analysis of the strong decays of the $Y(4660)$ in tetraquark scenario via the QCD sum rules

Motivated by the enigmatic vector charmonium-like states, we investigate the strong decay behaviors of four kinds of vector tetraquark states, which are possible candidates for the $Y(4660)$, within the framework of three-point QCD sum rules based on rigorous quark-hadron duality. We take into account the vacuum condensates up to dimension 5 on the QCD side, and obtain the hadronic coupling constants therefore the partial decay widths of those states. The predicted total width $61.5\pm7.3\,\rm{MeV}$ is in excellent agreement with the experimental data for the $Y(4660)$, which supports its interpretation as a $[sc][\bar{s}\bar{c}]$ tetraquark state with the $J^{PC}=1^{--}$.

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Two-body strong decays of the pseudoscalar hidden-charm tetraquark states via the QCD sum rules

In this work, we study the properties of the pseudoscalar hidden-charm tetraquark states by analyzing their two-body strong decays via the QCD sum rules based on rigorous quark-hadron duality. We take into account the vacuum condensates up to dimension 5 on the QCD side, and obtain the hadronic coupling constants. At last, we obtain the total decay widths $Γ(Z_{c}^{-}) = 326.20^{+4.26}_{-3.11}$ MeV and $Γ(Z_{c}^{+}) = 91.84^{+0.96}_{-0.76}$ MeV, respectively, where the $Z_{c}^{+}$($J^{PC}=0^{-+}$) and $Z_{c}^{-}$($J^{PC}=0^{--}$) denote the pseudoscalar hidden-charm tetraquarks with the diquark-antidiquark structures $[uc]_{A}[\bar{d}\bar{c}]_{V}-[uc]_{V}[\bar{d}\bar{c}]_{A}$ and $[uc]_{A}[\bar{d}\bar{c}]_{V}+[uc]_{V}[\bar{d}\bar{c}]_{A}$, respectively.

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Harmonic K-quasiconformal Koebe functions: construction and application to Pavlovic's problem

We first construct the harmonic K-quasiconformal Koebe functions, filling a long-standing foundational gap in geometric function theory. This construction provides a unified parametric candidate extremal function framework for conformal mappings, quasiconformal mappings, and harmonic mappings, and we formulate related conjectures for the extremal theory of harmonic K-quasiconformal mappings. By combining this construction with Astala and Koskela's Hp-theory for quasiconformal mappings, we establish a sharp result concerning the optimal order of harmonic K-quasiconformal mappings with bounded Schwarzian norm in harmonic Hardy spaces. Motivated by the work of Chuaqui, Hernandez, and Martin [Math. Ann. 367, 1099-1122, 2017], this result gives a partial solution to Pavlovic's 2014 open problem on the embeddings of harmonic quasiconformal mappings into Hardy spaces, and outlines a path toward its complete solution.

math.CV↗