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Zhi-Hui Guo

Publications and source records attributed to Zhi-Hui Guo.

At least 55 records · Page 3Linked to original sources
arXiv2021

Insights into the inner structures of the fully charmed tetraquark state $X(6900)$

The recently discovered fully charmed tetraquark candidate $X(6900)$ is analyzed within the frameworks of effective-range expansion, compositeness relation and width saturation, and a coupled multichannel dynamical study. By taking into account constraints from heavy-quark spin symmetry, the coupled-channel amplitude including the $J/ψJ/ψ,~ χ_{c0}χ_{c0}$ and $χ_{c1}χ_{c1}$ is constructed to fit the experimental di-$J/ψ$ event distributions around the energy region near $6.9$ GeV. Another dynamical two-coupled-channel amplitude with the $J/ψJ/ψ$ and $ψ(3770) J/ψ$ is also considered to describe the same datasets. The three different theoretical approaches lead to similar conclusions that the two-meson components do not play dominant roles in the $X(6900)$. Our determinations of the resonance poles in the complex energy plane from the refined coupled-channel study are found to be consistent with the experimental analyses. The coupled-channel amplitudes also have another pole corresponding to a narrow resonance $X(6825)$ that we predict sitting below the $χ_{c0}χ_{c0}$ threshold and of molecular origin. We give predictions to the line shapes of the $χ_{c0}χ_{c0}$ and $χ_{c1}χ_{c1}$ channels, which could provide a useful guide for future experimental measurements.

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arXiv2021

A unified description of the hidden-charm tetraquark states $Z_{cs}(3985)$, $Z_c(3900)$ and $X(4020)$

The newly observed hidden-charm tetraquark state $Z_{cs}(3985)$, together with $Z_c(3900)$ and $X(4020)$, are studied in the combined theoretical framework of the effective range expansion, compositeness relation and the decay width saturation. The elastic effective-range-expansion approach leads to sensible results for the scattering lengths, effective ranges and the compositeness coefficients, $i.e.$, the probabilities to find the two-charm-meson molecule components in the tetraquark states. The coupled-channel formalism by including the $J/ψπ$ and $D\bar{D}^*/\bar{D}D^*$ to fulfill the constraints of the compositeness relation and the decay width, confirms the elastic effective-range-expansion results for the $Z_c(3900)$, by using the experimental inputs for the ratios of the decay widths between $D\bar{D}^*/\bar{D}D^*$ and $J/ψπ$. With the results from the elastic effective-range-expansion study as input for the compositeness, we generalize the discussions to the $Z_{cs}(3985)$ by including the $J/ψK^{-}$ and $D_s^{-}D^{*0}/D_s^{*-}D^{0}$, and predict the partial decay widths of the $J/ψK^{-}$. Similar calculations are also carried out for the $X(4020)$ by including the $h_cπ$ and $D^*\bar{D}^*$, and the partial decay widths of the $h_cπ$ is predicted. Our results can provide useful guidelines for future experimental measurements.

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arXiv2020

Light-flavor resonance dynamics in the $U(3)$ chiral theory

We review the recent developments on the light-flavor resonances in the $U(3)$ chiral effective filed theory. The spectral function sum rules and the semilocal duality in the scattering, which will be focus of this note, can provide us interesting and useful theoretical objects to bridge the hadron resonances in the intermediate energy region and the QCD behaviors in the asymptotic region. First the calculations of the meson-meson scattering amplitudes and factor factors are elaborated. The scalar spectral functions are then calculated in terms of the unitarized scalar form factors. The scalar and pseudoscalar spectral function sum rules in our study are found to be consistent with the asymptotic behavior of QCD in the chiral limit. The semilocal duality is found to be generally well satisfied, indicating the necessary cancellations of different contributions from different resonances indeed happen in the scattering amplitudes. The $N_C$ evolutions of the resonance poles, the ratios to quantify the semilocal duality and the spectral function integrals are also paid special attention to in this note.

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arXiv2020

Thermal behaviors of light scalar resonances at low temperatures

We study the thermal properties of the lowest multiplet of the QCD light-flavor scalar resonances, including the $f_0(500)/σ$, $K_{0}^{*}(700)/κ$, $f_0(980)$ and $a_0(980)$, in the framework of unitarized $U(3)$ chiral perturbation theory. After the successful fits to the meson-meson scattering inputs, such as the phase shifts and inelasticities, we obtain the unknown parameters and further calculate the resonance poles and their residues at zero temperature. By including the finite-temperature effects in the unitarized meson-meson scattering amplitudes, the thermal behaviors of the scalar resonance poles in the complex energy plane are studied. The masses of $σ$ and $κ$ are found to considerably decrease when increasing the temperatures, while their widths turn out to be still large when the temperatures reach around $200$ MeV. In contrast, both the masses and widths of the $f_0(980)$ and $a_0(980)$ are only slightly changed.

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arXiv2019

Effective-range-expansion study of near threshold heavy-flavor resonances

In this work we study the resonances near the thresholds of the open heavy-flavor hadrons using the effective-range-expansion method. The unitarity, analyticity and compositeness coefficient are also taken into account in our theoretical formalism. We consider the $Z_c(3900)$, $X(4020)$, $χ_{c1}(4140)$, $ψ(4260)$ and $ψ(4660)$. The scattering lengths and effective ranges from the relevant elastic $S$-wave scattering amplitudes are determined. Tentative discussions on the inner structures of the aforementioned resonances are given.

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arXiv2019

Anatomy of the newly observed hidden-charm pentaquark states: $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$

We study the newly reported hidden-charm pentaquark candidates $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ from the LHCb Collaboration, in the framework of the effective-range expansion and resonance compositeness relations. The scattering lengths and effective ranges from the $S$-wave $Σ_c\bar{D}$ and $Σ_c\bar{D}^*$ scattering are calculated by using the experimental results of the masses and widths of the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$. Then we calculate the couplings between the $J/ψp,\,Σ_c\bar{D}$ channels and the pentaquark candidate $P_c(4312)$, with which we further estimate the probabilities of finding the $J/ψp$ and $Σ_c\bar{D}$ components inside $P_c(4312)$. The partial decay widths and compositeness coefficients are calculated for the $P_c(4440)$ and $P_c(4457)$ states by including the $J/ψp$ and $Σ_c\bar{D}^*$ channels. Similar studies are also carried out for the three $P_c$ states by including the $Λ_c\bar{D}^{*}$ and $Σ_c\bar{D}^{(*)}$ channels.

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arXiv2018

Resonance properties from lattice energy levels using chiral effective field theory

We use the chiral effective field theory to study the lattice finite-volume energy levels from the meson-meson scattering. The hadron resonance properties and the scattering amplitudes at physical masses are determined from the lattice energy levels calculated at unphysically large pion masses. The results from the $πη, K\bar{K}$ and $πη'$ coupled-channel scattering and the $a_0(980)$ resonance are explicitly given as a concrete example.

hep-lat↗
arXiv2018

Updated study of the $η$-$η'$ mixing and the thermal properties of light pseudoscalar mesons at low temperatures

Within the framework of the $U(3)$ chiral perturbation theory, we revisit the masses, decay constants and the mixing parameters of the light pseudoscalar mesons $π, K, η$ and $η'$. The low energy constants up to next-to-next-to-leading order are determined by including the light-quark mass dependences of the various quantities from different lattice QCD simulations and relevant phenomenological inputs. Then we study the finite-temperature behaviors of the masses of the light pseudoscalar mesons. The thermal behaviors of the $η$-$η'$ mixing angles in singlet-octet and quark-flavor bases are also explored. While the masses of the $π, K$, and $η$ are increased when increasing the temperatures, the mass of the $η'$ turns out to be slightly decreased in the low-temperature region.

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arXiv2018

Towards a precise determination of the scattering amplitudes of the charmed and light-flavor pseudoscalar mesons

We study the scattering of the light-flavor pseudoscalar mesons ($π, K, η$) off the ground-state charmed mesons ($D,D_s$) within chiral effective field theory. The recent lattice simulation results on various scattering lengths and the finite-volume spectra both in the moving and center-of-mass frames, most of which are obtained at unphysical meson masses, are used to constrain the free parameters in our theory. Explicit formulas to include the $S$- and $P$-wave mixing to determine the finite-volume energy levels are provided. After a successful reproduction of the lattice data, we perform a chiral extrapolation to predict the quantities with physical meson masses, including phase shifts, inelasticities, resonance pole positions and the corresponding residues from the scattering of the light pseudoscalar and charmed mesons.

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arXiv2017

Prediction of exotic doubly charmed baryons within chiral effective field theory

In this work we study the possible QCD exotic states in the doubly charmed baryon sector. Within chiral effective theory, it is predicted that several excited baryons result from the $S$-wave scattering of ground-state doubly charmed baryons ($Ξ_{cc}^{++}, Ξ_{cc}^{+}, Ω_{cc}^{+}$) and light pseudoscalar mesons ($π, K, η$). The excited doubly charmed baryons can be classified by the strangeness ($S$) and isospin ($I$) quantum numbers. Two of the excited states are clearly exotic, in the sense that they cannot be explained by the conventional baryons with three quarks, since their quantum numbers are $(S,I)=(1,0)$ and $(-1,1)$. Similar to the charmed scalar meson $D_{s0}^{*}(2317)$ in $DK$ scattering and the hyperon $Λ(1405)$ in $\bar{K}N$ scattering, one bound state below the $Ξ_{cc} \bar{K}$ threshold is predicted in the $(S,I)=(-1,0)$ channel. In addition, two resonant structures are found in the $Ξ_{cc}π, Ξ_{cc}η$ and $Ω_{cc} K$ coupled-channel scattering with $(S,I)=(0,1/2)$. The corresponding pole positions and coupling strengths of the excited doubly charmed baryons are given. The scattering lengths of the ground-state doubly charmed baryons and light pseudoscalar mesons are also predicted. The current study may provide useful guides for future experimental measurements and lattice simulations.

hep-ph↗
arXiv2017

Chiral study of the $a_0(980)$ resonance and $πη$ scattering phase shifts in light of a recent lattice simulation

We investigate the $a_0(980)$ resonance within chiral effective field theory through a three-coupled-channel analysis, namely $πη$, $K\bar{K}$ and $πη'$. A global fit to recent lattice finite-volume energy levels from $πη$ scattering and relevant experimental data on a $πη$ event distribution and the $γγ\toπη$ cross section is performed. Both the leading and next-to-leading-order analyses lead to similar and successful descriptions of the finite-volume energy levels and the experimental data. However, these two different analyses yield different $πη$ scattering phase shifts for the physical masses for the $π, K, η$ and $η'$ mesons. The inelasticities, the pole positions in the complex energy plane and their residues are calculated both for unphysical and physical meson masses.

hep-ph↗
arXiv2016

$Z_c(3900)$ as a $D\bar{D}^*$ molecule from the pole counting rule

A comprehensive study on the nature of the $Z_c(3900)$ resonant structure is carried out in this work. By constructing the pertinent effective Lagrangians and considering the important final-state-interaction effects, we first give a unified description to all the relevant experimental data available, including the $J/ψπ$ and $ππ$ invariant mass distributions from the $e^+e^-\to J/ψππ$ process, the $h_cπ$ distribution from $e^+e^-\to h_cππ$ and also the $D\bar D^{*}$ spectrum in the $e^+e^-\to D\bar D^{*}π$ process. After fitting the unknown parameters to the previous data, we search the pole in the complex energy plane and find only one pole in the nearby energy region in different Riemann sheets. Therefore we conclude that $Z_c(3900)$ is of $D\bar D^*$ molecular nature, according to the pole counting rule method~[Nucl.~Phys.~A543, 632 (1992); Phys.~Rev.~D 35,~1633 (1987)]. We emphasize that the conclusion based upon the pole counting method is not trivial, since both the $D\bar D^{*}$ contact interactions and the explicit $Z_c$ exchanges are introduced in our analyses and they lead to the same conclusion.

hep-ph↗
arXiv2016

Probabilistic interpretation of compositeness relation for resonances

Bound, antibound and resonance states are associated to poles in the on-shell partial wave amplitudes. We show here that from the residues of the pole a rank 1 projection operator associated with any of these states can be extracted, in terms of which a sum rule related to the composition of the state can be derived. Although typically it involves complex coefficients for the compositeness and elementariness, except for the bound state case, we demonstrate that one can formulate a meaningful compositeness relation with only positive coefficients for resonances whose associated Laurent series in the variable s converges in a region of the physical axis around Re(s_P), with s_P the pole position of the resonance. It is also shown that this result can be considered as an analytical extrapolation in s_P of the clear narrow resonance case. We exemplify this formalism to study the two-body components of several resonances of interest.

hep-ph↗
arXiv2016

The $Λ_c(2595)$ resonance as a dynamically generated state: the compositeness condition and the large $N_c$ evolution

Recent studies have shown that the well established $Λ_c(2595)$ resonance contains a large meson-baryon component, which can vary depending on the specific formalism. In this work, we examine such a picture by utilizing the compositeness condition and the large number of colors ($N_c$) expansion. We examine three different models fulfilling two body unitarity in coupled-channels, and adopting renormalization schemes where the mass of the $Λ_c(2595)$ resonance is well described, but not necessarily its width, since we do not consider three body channels and work at the isospin symmetric limit. Both approximations might have an effect larger on the width than on the mass. In this context, our studies show that the compositeness of the $Λ_c(2595)$ depends on the number of considered coupled channels, and on the particular regularization scheme adopted in the unitary approaches and, therefore, is model dependent. In addition, we perform an exploratory study of the $Λ_c(2595)$ in the large $N_c$ expansion, within a scheme involving only the $πΣ_c$ and $KΞ'_c$ channels, whose dynamics is mostly fixed by chiral symmetry. In this context and formulating the leading-order interaction as a function of $N_c$, we show that for moderate $N_c> 3$ values, the mass and width of the $Λ_c(2595)$ deviate from those of a genuine $qqq$ baryon, implying the relevance of meson-baryon components in its wave function. Furthermore, we study the properties of the $Λ_c(2595)$, in the strict $N_c \to \infty $ limit, using an extension of the chiral Weinberg-Tomozawa interaction to an arbitrary number of flavors and colors. This latter study hints at the possible existence of a (perhaps) sub-dominant $qqq$ component in the $Λ_c(2595)$ resonance wave function, which would become dominant when the number of colors gets sufficiently large.

hep-ph↗
arXiv2016

General considerations on the nature of $Z_b(10610)$ and $Z_b(10650)$ from their pole positions

The nature of the bottomonium-like states $Z_b(10610)$ and $Z_b(10650)$ is studied by calculating the $B^{(*)}\overline B^{*}$ compositeness ($X$) in those resonances. We first consider uncoupled isovector $S$-wave scattering of $B^{(*)}\overline B^{*}$ within the framework of effective-range expansion (ERE). Expressions for the scattering length ($a$) and effective range ($r$) are derived exclusively in terms of the masses and widths of the two $Z_b$ states. We then develop compositeness within ERE for the resonance case and deduce the expression $X=1/\sqrt{2r/a-1}$, which is then applied to the systems of interest. Finally, the actual compositeness parameters are calculated in terms of resonance pole positions and their experimental branching ratios into $B^{(*)}\overline{B}^*$ by using the method of Ref.[1]. We find the values $X=0.66\pm 0.11$ and $0.51\pm 0.10$ for the $Z_b(10610)$ and $Z_b(10650)$, respectively. We also compare the ERE with Breit-Wigner and Flatté parameterizations to discuss the applicability of the last two ones for near-threshold resonances with explicit examples.

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arXiv2016

Resonance on top of thresholds: the $Λ_c(2595)^+$ as an extremely fine-tuned state

A dedicated study of the $πΣ_c$ scattering around its threshold is carried out in this work to probe the nature of $Λ_c(2595)^+$. We first demonstrate that the effective range expansion approach fails to work near the $Λ_c(2595)^+$ pole position, due to the presence of a nearby CDD pole around the $πΣ_c$ thresholds. We then develop a general framework to properly handle the situation with a CDD pole accompanied by nearby thresholds, which is first elaborated for the single-channel case and then generalized to the coupled-channel study. The isospin breaking effects of the three $πΣ_c$ channels with different thresholds are specially taken into account in our study. The finite-width effects from the $Σ_c$ baryons are considered and found to be relevant to give the $Λ_c(2595)^+$ width fully compatible to its experimental value. Through the compositeness analysis, our robust conclusion is that the $π^0Σ_c^+$ component is subdominant inside the $Λ_c(2595)^+$.

hep-ph↗
arXiv2015

New insights into the $D^{*}_{s0}(2317)$ and other charm scalar mesons

Through the scattering of light-pseudoscalar mesons ($π,K,η,η'$) off charmed mesons ($D, D_s$), we study the $D^{*}_{s0}(2317)$ state and other relevant charm scalar mesons in a unitarized chiral effective field theory approach. We investigate the charm scalar meson poles with different strangeness ($S$) and isospin ($I$) quantum numbers as well as their corresponding residues, which provide the coupling strengths of the charm scalar mesons. Both the light-quark mass and $N_C$ dependences of the pole positions of the $D^{*}_{s0}(2317)$ and the poles with $(S,I)=(0,1/2)$ are analyzed in detail in this work. Interestingly we observe quite similar pion mass trajectories for the resonance pole at around 2.1 GeV with $(S,I)=(0,1/2)$ to those of the $f_0(500)$ given in the literature. When increasing the values of $N_C$ we find that a bound state and a virtual state in the $(S,I)=(1,0)$ channel asymmetrically approach the $D K$ threshold for $N_C<6$, and they meet at this threshold at $N_C=6$. When $N_C>6$, the bound and virtual states move into the complex plane on the second Riemann sheet and become a symmetric pair of resonance poles. For large enough values of $N_C$, neither the $D^{*}_{s0}(2317)$ pole nor the poles with $(S,I)=(0,1/2)$ tend to fall down to the real axis, indicating that they do not behave like a standard quark-antiquark meson at large $N_C$.

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