arXiv subjects

Zhi-Gang Wang

Publications and source records attributed to Zhi-Gang Wang.

At least 73 records · Page 4Linked to original sources

arXiv2024

Doubly-Charm and Doubly-Bottom Pentaquark molecular States via the QCD sum rules

In the present work, the doubly-charm and doubly-bottom pentaquark molecular states $D^{(*)}Σ_c^{(*)}$ and $B^{(*)}Σ_b^{(*)}$ are studied via the QCD sum rules. Sixteen color singlet-singlet type currents with the definite isospin-spin-parity $IJ^P$ are constructed to interpolate the corresponding hadronic states with the same quantum numbers. The masses and pole residues of those doubly-heavy pentaquark molecular states are calculated, the results show that their masses are all below the corresponding meson-baryon thresholds, which means that they are possible bound states, not resonant states, moreover, the possible decay channels for the doubly-charm molecular states are given.

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arXiv2024

Decipher the width of the $X(3872)$ via the QCD sum rules

In this work, we take the $X(3872)$ as the hidden-charm tetraquark state with both isospin $I=0$ and $1$ components, then investigate the strong decays $X(3872)\to J/ψπ^+π^-$, $J/ψω$, $χ_{c1}π^0$, $D^{*0}\bar{D}^0$ and $D^{0}\bar{D}^0π^0$ with the QCD sum rules. We take account of all the Feynman diagrams, and acquire four QCD sum rules based on rigorous quark-hadron duality. We obtain the total decay width about $1\,\rm{MeV}$, which is in excellent agreement with the experiment data $ Γ_{X}=1.19\pm 0.21\,\rm{MeV}$ from the Particle Data Group, it is the first time to reproduce the tiny width of the $X(3872)$ via the QCD sum rules, which supports assigning the $X(3872)$ as the hidden-charm tetraquark state with the $J^{PC}=1^{++}$.

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arXiv2024

Analysis of the electromagnetic form factors and the radiative decays of the vector heavy-light mesons

In this article, we analyze the electromagnetic form factors of the vector heavy-light mesons to the pseudoscalar heavy-light mesons in the framework of three-point QCD sum rules, where the contributions of vacuum condensate terms $\langle\overline{q}q\rangle$, $\langle\overline{q}g_{s}σGq\rangle$, $\langle g_{s}^{2}G^{2}\rangle$, $\langle f^{3}G^{3}\rangle$ and $\langle\overline{q}q\rangle\langle g_{s}^{2}G^{2}\rangle$ are considered. With these results, we also obtain the radiative decay widths of the vector heavy-light mesons and then compare our results with those of other collaboration's. The final results about the radiative decay widths are $Γ(D^{*0}\to D^{0}γ)=1.74^{+0.40}_{-0.37}$ keV, $Γ(D^{*+}\to D^{+}γ)=0.17^{+0.08}_{-0.07}$ keV, $Γ(D_{s}^{*}\to D_{s}γ)=0.029^{+0.009}_{-0.008}$ keV, $Γ(B^{*0}\to B^{0}γ)=0.018^{+0.006}_{-0.005}$ keV, $Γ(B^{*+}\to B^{+}γ)=0.015^{+0.007}_{-0.007}$ keV and $Γ(B^{*}_{s}\to B_{s}γ)=0.016^{+0.003}_{-0.005}$ keV.

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arXiv2024

Analysis of the vector hidden-charm-hidden-strange tetraquark states with implicit P-waves

We take the scalar, pseudoscalar, axialvector, vector and tensor diquarks as the basic building blocks to construct the four-quark currents with implicit P-waves, and investigate the hidden-charm-hidden-strange tetraquark states with the $J^{PC}=1^{--}$ and $1^{-+}$ via the QCD sum rules in a comprehensive and consistent way, and revisit the assignments of the $X/Y$ states, especially the $Y(4500)$, $X(4630)$, $Y(4660)$, $Y(4710)$ and $Y(4790)$, in the tetraquark picture.

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arXiv2024

Heavy quark dominance in orbital excitation of singly and doubly heavy baryons

A mechanism of the heavy quark dominance in the orbital excitation is proposed in this paper which is testified to be reasonable for singly and doubly heavy baryons. In the relativistic quark model, an analysis of the Hamiltonian figures out the mechanism that the excitation mode with lower energy levels is always associated with the heavy quark(s), and the splitting of the energy levels is suppressed by the heavy quark(s). So, the heavy quarks dominate the orbital excitation of singly and doubly heavy baryons. Furthermore, a physical understanding of this mechanism is given in a semi-classical way. Accordingly, the predicted mass spectra of singly and doubly heavy baryons confirm the rationality of this mechanism. In addition, an interesting consequence of this mechanism is that a heavy-light meson is more likely to be produced in the strong decay of the high-orbital excited states, which is supported by experiments. This mechanism is rooted in the breakdown of the mass symmetry. Therefore, it may be also valid for other multi-quark systems, such as the tetraquarks Qqqq and QQqq, or the pentaquarks Qqqqq and QQqqq.

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arXiv2024

Strong decays of the $P_c(4312)$ and its isospin cousin via the QCD sum rules

In the present work, considering the conservation of isospin in the strong decays, we investigate the strong decays of the pentaquark molecule candidate $P_c(4312)$ and its possible higher isospin cousin $P_c(4330)$ in the framework of the QCD sum rules. What's more, the pole residue of the $Δ$ baryon with isospin eigenstate $|II_3\rangle=|\frac{3}{2}\frac{1}{2}\rangle$ is obtained. If the possible pentaquark molecule candidate $P_c(4330)$ could be testified in the future experiment, it would shed light on interpretations of the $P_c$ states.

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arXiv2023

The fully-light vector tetraquark states with explicit P-wave via the QCD sum rules

In this paper, we apply the QCD sum rules to study the vector fully-light tetraquark states with an explicit P-wave between the diquark and antidiquark pair. We observed that the $Cγ_α\otimes\stackrel{\leftrightarrow}{\partial}_μ\otimesγ^αC$ (or $Cγ_α\otimes\stackrel{\leftrightarrow}D_μ\otimesγ^αC$) type current with fully-strange quarks couples potentially to a tetraquark state with the mass $2.16 \pm 0.14 \,\rm{GeV}$, which supports assigning the $Y/ϕ(2175)$ as the diquark-antidiquark type tetraquark state with the $J^{PC}=1^{--}$. The $qs\bar{q}\bar{s}$ and $ss\bar{s}\bar{s}$ vector tetraquark states with the structure $Cγ_μ\otimes \stackrel{\leftrightarrow}{\partial}_α\otimesγ^αC + Cγ^α\otimes\stackrel{\leftrightarrow}{\partial}_α\otimesγ_μ$ (or $Cγ_μ\otimes \stackrel{\leftrightarrow}D_α\otimesγ^αC + Cγ^α\otimes\stackrel{\leftrightarrow}D_α\otimesγ_μ$) are consistent with the $X(2200)$ and $X(2400)$ respectively, which lie in the region $2.20$ to $2.40\,\rm{GeV}$. The central values of the masses of the fully-strange vector tetraquark states with an explicit P-wave are about $2.16-3.13\,\rm{GeV}$ (or $2.16-3.16\,\rm{GeV}$), and the predictions for other fully-light vector tetraquark states with and without hidden-strange are also presented.

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arXiv2023

The two-body strong decays of the fully-charm tetraquark states

We study the hadronic coupling constants in the two-body strong decays of the fully-charm tetraquark states with the $J^{PC}=0^{++}$, $1^{+-}$ and $2^{++}$ via the QCD sum rules based on rigorous quark-hadron duality. Then we obtain the hadronic coupling constants and partial decay widths therefore total decay widths, which support assigning the $X(6552)$ as the first radial excitation of the scalar tetraquark state. And other predictions can be used to diagnose exotic states in the future.

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arXiv2023

Three-body strong decays of the $Y(4230)$ via the light-cone QCD sum rules

We tentatively assign the $Y(4230)$ as the vector tetraquark state with a relative P-wave between the scalar diquark pair, and explore the three-body strong decays $Y(4230) \to \bar{D}^{*-}D^{*0}π^+$, $\bar{D}^{*-}D^0π^+$, $J/ψπ^+π^- $ and $ J/ψK^+K^-$ with the light-cone QCD sum rules by assuming contact four-meson coupling constants. The resulting partial decay widths are too small to account for the experimental data, and we expect those decays take place through an intermediate meson. We can search for the intermediate states and precisely measure the branching fractions to diagnose the nature of the $Y$ states.

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arXiv2023

Analysis of the strong vertices of $Σ_{c}ΔD^{}$ and $Σ_{b}ΔB^{}$ in QCD sum rules

In this work, we analyze the strong vertices $Σ_{c}ΔD^{*}$ and $Σ_{b}ΔB^{*}$ using the three-point QCD sum rules under the tensor structures $iε^{ρταβ}p_αp'_β$, $p^ρp'^τ$ and $p^ρp^τ$. We firstly calculate the momentum dependent strong coupling constants $g(Q^{2})$ by considering contributions of the perturbative part and the condensate terms $\langle\overline{q}q\rangle$, $\langle g_{s}^{2}GG \rangle$, $\langle\overline{q}g_{s}σGq\rangle$ and $\langle\overline{q}q\rangle^{2}$. By fitting these coupling constants into analytical functions and extrapolating them into time-like regions, we then obtain the on-shell values of strong coupling constants for these vertices. The results are $g_{1Σ_{c}ΔD^{*}}=5.13^{+0.39}_{-0.49}$ GeV$^{-1}$, $g_{2Σ_{c}ΔD^{*}}=-3.03^{+0.27}_{-0.35}$ GeV$^{-2}$, $g_{3Σ_{c}ΔD^{*}}=17.64^{+1.51}_{-1.95}$ GeV$^{-2}$, $g_{1Σ_{b}ΔB^{*}}=20.97^{+2.15}_{-2.39}$ GeV$^{-1}$, $g_{2Σ_{b}ΔB^{*}}=-11.42^{+1.17}_{-1.28}$ GeV$^{-2}$ and $g_{3Σ_{b}ΔB^{*}}=24.87^{+2.57}_{-2.82}$ GeV$^{-2}$. These strong coupling constants are important parameters which can help us to understand the strong decay behaviors of hadrons.

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arXiv2023

The strong vertices of bottom mesons $B$, $B^{*}$ and bottomonia $Υ$, $η_{b}$

In this article, the strong coupling constants of vertices $BBΥ$, $BB^{*}Υ$, $B^{*}B^{*}Υ$, $BB^{*}η_{b}$ and $B^{*}B^{*}η_{b}$ are analyzed in the framework of QCD sum rules. In this work, all possible off-shell cases and the contributions of vacuum condensate terms including $\langle\overline{q}q\rangle$, $\langle\overline{q}g_{s}σGq\rangle$, $\langle g_{s}^{2}G^{2}\rangle$, $\langle f^{3}G^{3}\rangle$ and $\langle\overline{q}q\rangle\langle g_{s}^{2}G^{2}\rangle$ are considered. The momentum dependent strong coupling constants are first calculated and then are fitted into analytical functions $g(Q^{2})$ which are used to extrapolate into time-like regions to obtain the final values of strong coupling constants. The final results are $g_{BBΥ}=40.67^{+7.55}_{-4.20}$, $g_{BB^{*}Υ}=11.58^{+2.19}_{-1.09}$ GeV$^{-1}$, $g_{B^{*}B^{*}Υ}=57.02^{+5.32}_{-5.31}$, $g_{BB^{*}η_{b}}=23.39^{+4.74}_{-2.30}$ and $g_{B^{*}B^{*}η_{b}}=12.49^{+2.12}_{-1.35}$ GeV$^{-1}$. These strong coupling constants are important input parameters which reflect the dynamic properties of the interactions among the mesons and quarkonia.

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arXiv2023

The strong vertices of charmed mesons $D$, $D^{*}$ and charmonia $J/ψ$, $η_{c}$

In this work, the strong coupling constants of the vertices $DDJ/ψ$, $DD^{*}J/ψ$, $D^{*}D^{*}J/ψ$, $DD^{*}η_{c}$ and $D^{*}D^{*}η_{c}$ are calculated within the framework of the QCD sum rules. For each vertex, we analyze the momentum dependence of the coupling constants by considering all possible off-shell cases. In these analyses, we consider the contributions of the vacuum condensate terms $\langle\overline{q}q\rangle$, $\langle\overline{q}g_{s}σGq\rangle$, $\langle g_{s}^{2}G^{2}\rangle$, $\langle f^{3}G^{3}\rangle$ and $\langle\overline{q}q\rangle\langle g_{s}^{2}G^{2}\rangle$. Then, the momentum dependent coupling constants are fitted into analytical functions $g(Q^2)$ and are extrapolated into time-like regions. The values of strong coupling constants are obtained by using on-shell conditions of the intermediate mesons($Q^2=-m^2$). The final results are as follows, $g_{DDJ/ψ}=5.01^{+0.58}_{-0.16}$, $g_{DD^{*}J/ψ}=3.55^{+0.20}_{-0.21}$GeV$^{-1}$, $g_{D^{*}D^{*}J/ψ}=5.10^{+0.59}_{-0.43}$, $g_{DD^{*}η_{c}}=3.68^{+0.39}_{-0.11}$ and $g_{D^{*}D^{*}η_{c}}=4.87^{+0.42}_{-0.40}$GeV$^{-1}$.

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arXiv2023

The singly-charmed pentaquark molecular states via the QCD sum rules

In this work, we systematically investigate the singly-charmed pentaquark molecular states $D^{(*)}N$, $D^{(*)}Ξ^{(*)}$ and $D_s^{(*)}Ξ^{(*)}$ with the QCD sum rules by carrying out the operator product expansion up to the vacuum condensates of dimension 13 and taking fully account of the light-flavor $SU(3)$ breaking effects. The numerical results favor assigning the $Ω_c(3185)$ as the $DΞ$ molecular state with the $J^P=\frac{1}{2}^-$ and $| I,I_3 \rangle=| 0,0 \rangle$, assigning the $Ω_c(3327)$ as the $D^*Ξ$ molecular state with the $J^P=\frac{3}{2}^-$ and $|I,I_3 \rangle=| 0,0 \rangle$, assigning the $Σ_c(2800)$ as the $DN$ molecular state with the $J^P=\frac{1}{2}^-$ and $| I,I_3 \rangle=| 1,0 \rangle$, and assigning the $Λ_c(2940)/Λ_c(2910)$ as the $D^*N$ molecular state with the $J^P=\frac{3}{2}^-$ and $| I,I_3 \rangle=| 0,0 \rangle$. Other potential molecule candidates are also predicted, which may be observed in future experiments. For example, we can search for the $DΞ$ and $D^*Ξ$ molecular states with the isospin $| I,I_3 \rangle=| 1,\pm1 \,\rangle$ in the $Ξ_c^+\bar{K}^0$ and $Ξ_c^0\bar{K}^-$ mass spectrum respectively in the future, which could shed light on the nature of the $Ω_c(3185/3327)$.

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arXiv2023

The $Λ$-type P-wave bottom baryon states via the QCD sum rules

Our study focuses on the $Λ$-type P-wave bottom baryon states with the spin-parity $J^P=\frac{1}{2}^-$, $\frac{3}{2}^-$. We introduce an explicit P-wave between the two light quarks in the interpolating currents (and the two light quarks are antisymmetric in flavor space, therefore leads to the name $Λ$-type baryon) to investigate the $Λ_b$ and $Ξ_b$ states within the framework of the full QCD sum rules. The predicted masses show that the $Ξ_b(6087)$ and $Ξ_b(6095/6100)$ could to be the P-wave bottom-strange baryon states with the spin-parity $J^P=\frac{1}{2}^-$ and $\frac{3}{2}^-$, respectively, meanwhile, the $Λ_b(5912)$ and $Λ_b(5920)$ could be the P-wave bottom baryon states with the spin-parity $J^P=\frac{1}{2}^-$ and $\frac{3}{2}^-$, respectively. The $Λ_b(5920)$ and $Ξ_b(6095/6100)$ maybe have two remarkable under-structures or Fock components at least.

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arXiv2023

Systematic analysis of doubly charmed baryons $Ξ_{cc}$ and $Ω_{cc}$

In this work, we perform a systematic study of the mass spectra, the root mean square(r.m.s.) radii and the radial density distributions of the doubly charmed baryons $Ξ_{cc}$ and $Ω_{cc}$. The calculations are carried out in the frame work of Godfrey-Isgur (GI) relativized quark model, where the baryon is regarded as a real three-body system of quarks. Our results show that the excited energy of doubly charmed baryon with $ρ$-mode is lower than those of the $λ$-mode and $λ$-$ρ$ mixing mode, which indicates that the lowest state is dominated by the $ρ$-mode. According to this conclusion, we systematically investigate the mass spectra, the r.m.s. radii of the ground and excited states($1S\sim4S$, $1P\sim4P$, $1D\sim4D$, $1F\sim4F$ and $1G\sim4G$) with $ρ$-mode. Using the wave functions obtained from quark model, we also study the radial density distributions. Finally, with the predicated mass spectra, the Regge trajectories of $Ξ_{cc}$ and $Ω_{cc}$ in the ($J$,$M^{2}$) plane are constructed, and the slopes, intercepts are determined by linear fitting. It is found that model predicted masses fit nicely to the constructed Regge trajectories.

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arXiv2023

Analysis of the D-wave $Σ$-type charmed baryon states with the QCD sum rules

We construct the $Σ$-type currents to investigate the D-wave charmed baryon states with the QCD sum rules systematically. The predicted masses $M=3.35^{+0.13}_{-0.18}\,\rm{GeV}$ ($3.33^{+0.13}_{-0.16}\,\rm{GeV}$), $3.34^{+0.14}_{-0.18}\,\rm{GeV}$ ($3.35^{+0.13}_{-0.16}\,\rm{GeV}$) and $3.35^{+0.12}_{-0.13}\,\rm{GeV}$ ($3.35^{+0.12}_{-0.14}\,\rm{GeV}$) for the $Ω_c(0,2,{\frac{1}{2}}^+)$, $Ω_c(0,2,{\frac{3}{2}}^+)$ and $Ω_c(0,2,{\frac{5}{2}}^+)$ states are in excellent agreement with the experimental data $ 3327.1\pm1.2 \mbox{ MeV}$ from the LHCb collaboration, and support assigning the $Ω_c(3327)$ to be the $Σ$-type D-wave $Ω_c$ state with the spin-parity $J^P={\frac{1}{2}}^+$, ${\frac{3}{2}}^+$ or ${\frac{5}{2}}^+$.

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arXiv2023

Analysis of the decay $Y(4500)\to D^\bar{D}^π$ with the light-cone QCD sum rules

In this work, we tentatively assign the $Y(4500)$ as the $[uc]_{\tilde{A}}[\overline{uc}]_{V}+[uc]_{V}[\overline{uc}]_{\tilde{A}}+[dc]_{\tilde{A}}[\overline{dc}]_{V} +[dc]_{V}[\overline{dc}]_{\tilde{A}}$ tetraquark state with the quantum numbers $J^{PC}=1^{--}$, and study the three-body strong decay $Y(4500)\to D^{*-}D^{*0}π^+$ with the light-cone QCD sum rules. It is the first time to use the light-cone QCD sum rules to calculate the four-hadron coupling constants, the approach can be extended to study other three-body strong decays directly and diagnose the $X$, $Y$ and $Z$ states.

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arXiv2023

Strong decay properties of single heavy baryons $Λ_{Q}$, $Σ_{Q}$ and $Ω_{Q}$

Motivated by recent progresses in experiments in searching for the $Ω_{c}$ baryons, we systematically analyze the strong decay behaviors of single heavy baryons $Λ_{Q}$, $Σ_{Q}$ and $Ω_{Q}$. The two-body strong decay properties of $S$-wave, $P$-wave and some $D$-wave states are studied with the $^{3}P_{0}$ model. The results support assigning the recently observed $Ω_{c}(3185)$ and $Ω_{c}(3327)$ as the 2S($\frac{3}{2}^{+}$) and 1D($\frac{3}{2}^{+}$) states, respectively. In addition, the quantum numbers of many other experimentally observed baryons are also suggested according to their strong decays. Finally, some baryons which have good potentials to be observed in experiments are predicted and the possible decay channels for searching for these predicted states are also suggested.

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