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Zhi-Yong Zhou

Publications and source records attributed to Zhi-Yong Zhou.

At least 19 recordsLinked to original sources

On Compositeness of $D_{s0}^*(2317)$ and its decay to $D_sπ^0$

We demonstrate that the $D_{s0}^{*}(2317)$ can be described as a bound-state pole arising from the coupling between a discrete $c\bar{s}(1^3P_0)$ state and the $DK$ continuum state in the Lee-Friedrichs model. The elementariness and compositeness of the $D_{s0}^{*}(2317)$ are determined to be about $Z:X\approx 51.1 \%:48.9\%$, indicating a nearly equal admixture of compact quark-model state and hadronic molecular components. The decay width of $D_{s0}^{*}(2317)\rightarrow D_s^{+}π^0$ is evaluated within the quark rearrangement framework. The transition $c\bar{s}(1^3P_0)\rightarrow D_sπ^0$ proceeds via the OZI-allowed $c\bar{s}(1^3P_0)-D_sη$ coupling followed by $η-π^0$ mixing, which serves as the primary source of isospin violation in this channel. The coupling between $DK$ and $D_sπ^0$ is computed in a quark rearrangement model, where the isospin violation effect originates from the mass difference between the $D^0K^+$ and $D^+K^0$ thresholds. The parameters of the scheme shares the same ones with those of the underlying potential model and only the vacuum production strength is adjusted to reproduce the physical $D_{s0}^{*}(2317)$ mass. This calculation may shed more insight to the nature of exotic $D_{s0}^{*}(2317)$ state and its isospin-breaking decay properties.

hep-ph↗

Comparing relativistic and non-relativistic quark pair creation models

We investigate the strong decay properties of light unflavored and strange mesons within a relativistic quark-pair-creation (QPC) framework, and compare the results with those obtained in the conventional non-relativistic QPC model. Our analysis shows that, within the present theoretical and experimental uncertainties, the relativistic QPC model yields predictions for strong decay widths of comparable overall quality to those of the non-relativistic QPC model. This indicates that the non-relativistic QPC approach remains adequate for estimating decay widths in most practical applications. Nevertheless, owing to the inclusion of Lorentz boosts and Wigner rotations, the relativistic QPC model exhibits a stronger suppression of decay amplitudes in the high-energy region. This feature may be useful in studies based on unquenched quark models, where the relativistic QPC coupling could lead to more controlled meson-loop effects and mass shifts.

hep-ph↗

Understanding the 1P- and 2S-wave nucleon resonances within the extended Lee-Friedrichs Model

We present a unified desciption of the low-lying $1P$- and $2S$-wave nucleon resonance within the framework of an extended Lee-Friedrichs scheme. By incorporating the coupled-channel dynamics between bare quark-model states and the $πN$, $πΔ$ and $ηN$ meson-baryon continua, we examine the mass shifts and structural properties of these excited states. We demonstrate that when the model parameters are calibrated to match the $1P$-wave spectrum and their widths, the pole associated with the bare $2S$ state is naturally shifted downward to the mass region of physical Roper resonance--$N(1440)$, thereby offering a dynamical explanation for the long-standing level-inversion problem. An approximate analysis of compositeness and elementariness reveals that the Roper resonance contains a significant meson-baryon continuum states, consistent with the picture of a bare core heavily dressed by meson-baryon cloud. Simultaneously, the pole positions and properties of five $1P$-wave resonances--$N(1535)$, $N(1650)$, $N(1520)$, $N(1700)$ and $N(1675)$ are successfully reproduced. Our results highlight the essential role of coupled-channel effects in shaping the nucleon spectrum and provide a consistent microscopic insight into the interplay between internal quark degrees of freedom and external hadronic fields.

hep-ph↗

Radiative decays of $P$-wave charmed baryons in the $SU(3)$ flavor $\bf6_F$ representation

We perform a comprehensive investigation of the radiative decays of $P$-wave charmed baryons in the $SU(3)$ flavor $\mathbf{6}_F$ representation, employing the light-cone QCD sum rule approach within the framework of heavy quark effective theory. We analyze their electromagnetic transitions into ground-state charmed baryons via photon emission. When combined with the mass spectra and strong decay properties previously studied in Ref.~\cite{Yang:2021lce}, our results constitute a systematic and complete QCD sum rule analysis of the $P$-wave singly charmed baryons within the framework of heavy quark effective theory. As summarized in Table~\ref{tab:result}, several excited charmed baryons are found to possess suppressed strong decay widths, thereby rendering their radiative decay channels particularly significant for experimental identification and theoretical understanding.

hep-ph↗

Updated analysis of charmonium states in a relativized quark potential model

Motivated by recent experimental observations of charmonium(-like) states, we investigate their interpretation as conventional charmonium states within the framework of relativized quark potential model. We find a consistent description of the updated masses of charmonia, bottomonia and some selected charmed mesons, then systematically compute open-charm strong decay widths and electromagnetic transition widths for radially excited charmonium states up to $n=5$. The numerical results show significantly improved agreement with experimental masses and widths. Notably, the newly-observed $χ_{c1}(4010)$ and $χ_{c1}(4274)$ are tentatively associated with the $χ_{c1}(2P)$ and $χ_{c1}(3P)$ respectively, while the $χ_{c0}(4500)$ and $χ_{c0}(4700)$ are interpreted as the $χ_{c0}(4P)$ and $χ_{c0}(5P)$ states. For the controversial $χ_{c1}(3872)$ state, we suggest its potential connection to $χ_{c1}(4010)$, as a two-pole structure due to the $χ_{c1}(2P)$ coupling to $D\bar{D}$ channels. Intriguingly, the predicted mass of $χ_{c0}(2P)$ is about 3851 MeV, diverging from the original estimate of 3916 MeV in the Godfrey and Isgur's work but consistent with non-relativistic potential model predictions. This calculation might provide more insight to the future experimental investigation of charmonium(-like) states.

hep-ph↗

On the generalized Friedrichs-Lee model with multiple discrete and continuous states

In this study, we present several improvements of the non-relativistic Friedrichs-Lee model with multiple discrete and continuous states and still retain its solvability. Our findings establish a solid theoretical basis for the exploration of resonance phenomena in scenarios involving multiple interfering states across various channels. The scattering amplitudes associated with the continuum states naturally adhere to coupled-channel unitarity, rendering this framework particularly valuable for investigating hadronic resonant states appearing in multiple coupled channels. Moreover, this generalized framework exhibits a wide-range applicability, enabling investigations into resonance phenomena across diverse physical domains, including hadron physics, nuclear physics, optics, and cold atom physics, among others.

hep-ph↗

Strong decay properties of P-wave single bottom baryons of the SU(3) flavor antitriplet $\bf\bar 3_F$

We study the $P$-wave bottom baryons of the $SU(3)$ flavor antitriplet and systematically calculate their strong decay properties, including their $D$-wave decays into ground-state bottom baryons with light pseudoscalar mesons and $S$-wave decays into ground-state bottom baryons with light vector mesons. Together with Refs.~\cite{Tan:2023opd,Yang:2019cvw,Yang:2020zrh,Luo:2024jov}, a rather complete investigation has been performed to study their mass spectra and strong/radiative decay properties, through the methods of QCD sum rules and light-cone sum rules within the framework of heavy quark effective theory. Among various possibilities, we identify four $Λ_b$ and four $Ξ_b$ baryons, with limited decay widths and so capable of being observed in experiments. Their masses, mass splittings within the same multiplets, and strong/radiative decay widths are summarized in Table~\ref{tab:decayb3f} for future experimental searching.

hep-ph↗

Practical parametrization of two-pole structure

We suggest that the extended Lee-Friedrichs model could be directly used as a practical parametrization method for the experimental analysis of resonance structures. This parametrization incorporates the constraints of relativistic phase space and the threshold behavior, and respects both unitarity and analyticity constraints of the scattering amplitude. As such, the poles on unphysical Riemann sheets could be easily extracted. This parametrization method offers a comparable fit quality to the improved Breit-Wigner parametrization with an energy-dependent width function when the coupling strength is moderate. It is found that the parametrization could be used to correctly extract the poles near the physical region correctly. In particular, it can naturally incorporate the two-pole structure in which one pole is shifted from the discrete state and the other is dynamically generated. Moreover, the coupled-channel formulation of the extended Lee-Friedrichs parameterization is straightforward and its relationship with the Flatté parametrization form is discussed. Using $ρ(770)$, $Δ(1232)$, $K^*_0$ and $f_0$ states as illustrative examples, we demonstrate the effectiveness of this parametrization in capturing fit qualities and identifying relevant poles. It is illustrated that the $K_0^*(700)$ and $K_0^*(1430)$ could be perfectly parameterized in the Lee-Friedrichs form as a two-pole structure. A tentative investigation of $f_0$s in coupled-channel parametrization form are discussed, and a possible lineshape contributed by $χ_{c1}(3872)$ and $χ_{c1}(4012)$ is presented. The proposed parametrization scheme holds promise for future studies involving exotic hadron states near thresholds, offering a valuable tool for analyzing resonance structures in upcoming experimental investigations.

hep-ph↗

Reconciling experimental and lattice data of $Z_c(3900)$ in a $J/ψπ$-$D\bar{D}^*$ coupled-channel analysis

We study the $J/ψπ$ and $D\bar{D}^*$ coupled-channel system within a covariant framework. The $J/ψπ$ and $D\bar{D}^*$ invariant-mass distributions measured at 4.23~GeV and 4.26~GeV by BESIII and the finite-volume energy levels from recent lattice QCD simulations are simultaneously fitted. Phase shifts and inelasticities of the $J/ψπ$ and $D\bar{D}^*$ scattering are predicted using the resulting amplitudes. Poles corresponding to the $Z_c(3900)$ state are found in the complex energy plane and their couplings with $J/ψπ$ and $D\bar{D}^*$ are determined. Our results indicate that the current lattice data do not preclude the existence of a physical $Z_c(3900)$ state.

hep-ph↗

A new look at $ψ(4160)$ and $ψ(4230)$

By simultaneously analyzing the cross section data of $e^+e^-\rightarrow D\bar D, D\bar D^*, D^*\bar D^*, D\bar Dπ$ in a coupled-channel scheme with unitarity, we found that, in contrast to the conventional wisdom, the pole of $ψ(2^3D_1)$ might be located at about $\sqrt{s}=4222-32i\mathrm{MeV}$. This observation implies a possibility that the two resonances, dubbed the $ψ(4160)$ and $ψ(4230)$ in the PDG table now, might be the same $ψ(2^3D_1)$ state. Such a suggestion could provide more insight to our understanding the enigmatic decay properties of $ψ(4160)$ and $ψ(4230)$. Furthermore, this coupled-channel scheme could be applied to study other phenomena with several interfering resonances.

hep-ph↗

Scrutinizing $ππ$ scattering in light of recent lattice phase shifts

In this paper, the $IJ=00, 11, 20$ partial wave $ππ$ scattering phase shifts determined by the lattice QCD approach are analyzed by using a novel dispersive solution of the S-matrix, i.e. the PKU representation, in which the unitarity and analyticity of scattering amplitudes are automatically satisfied and the phase shifts are conveniently decomposed into the contributions of the cuts and various poles, including bound states, virtual states and resonances. The contribution of the left-hand cut is estimated by the $SU(2)$ chiral perturbation theory to $\mathcal{O}(p^4)$. The Balanchandran-Nuyts-Roskies relations are considered as constraints to meet the requirements of the crossing symmetry. It is found that the $IJ=00$ $ππ$ scattering phase shifts obtained at $m_π=391$ MeV by Hadron Spectrum Collaboration (HSC) reveal the presence of both a bound state pole and a virtual state pole below the $ππ$ threshold rather than only one bound state pole for the $σ$. To reproduce the lattice phase shifts at $m_π=391$ MeV, a virtual-state pole in the $IJ=20$ channel is found to be necessary in order to balance the left-hand cut effects from the chiral amplitudes. Similar discussions are also carried out for the lattice results with $m_π=236$ MeV from HSC. The observed behaviors of the pole positions with respect to the variation of the pion masses can provide deep insights into our understanding of the dynamical origin of $σ$ resonance.

hep-ph↗

Two-pole structures in a relativistic Friedrichs-Lee-QPC scheme

A general appearance of two-pole structures is exhibited in a relativistic Friedrichs-Lee model combined with a relativistic quark pair creation model in a consistent manner. This kind of two-pole structure could be found when a $q\bar q$ state couples to the open-flavor continuum state in the $S$ partial wave. We found that many enigmatic states, such as $f_0(500)/σ$, $K_0^*(700)/κ$, $a_0(980)$, $f_0(980)$, $D_0^*(2300)$, $D_{s0}^*(2317)$, and $X(3872)$, together with another higher state for each, all result from this kind of two-pole structures. Furthermore, an interesting observation is that this kind of two-pole structure will contribute roughly a total of 180$^\circ$ phase shift for the scattering process in a single channel approximation. This relativistic scheme may provide more insights into the understanding of the properties of non-$q\bar q$ state. It is also suggested that such two-pole structure could be a common phenomenon which deserves studying both from theoretical and experimental perspectives.

hep-ph↗

A Review on Partial-wave Dynamics with Chiral Effective Field Theory and Dispersion Relation

The description of strong interaction physics of low-lying resonances is out of the valid range of perturbative QCD. Chiral effective field theories have been developed to tackle the issue. Partial wave dynamics is the systematic tool to decode the underlying physics and reveal the properties of those resonances. It is extremely powerful and helpful for our understanding of the non-perturbative regime, especially when dispersion techniques are utilized simultaneously. Recently, plenty of exotic/ordinary hadrons have been reported by experiment collaborations, e.g. LHCb, Belle, and BESIII, etc.. In this review, we summarize the recent progress on the applications of partial wave dynamics combined with chiral effective field theories and dispersion relations, on related topics, with emphasis on $ππ$, $πK$, $πN$ and $\bar{K}N$ scatterings.

hep-ph↗

Relativistic Friedrichs-Lee model and quark-pair creation model

In this paper, we present how the Friedrichs-Lee model could be extended to the relativistic scenario and be combined with the relativistic quark pair creation model in a consistent way. This scheme could be applied to study the "unquenched" effect of the meson spectra. As an example, if the lowest $J^{PC}=0^{++}$ $(u\bar u+d\bar d)/\sqrt{2}$ bound state in the potential model is coupled to the $ππ$ continuum, two resonance poles could be found from the scattering amplitude for the continuum states. One of them could correspond to the $f_0(500)/σ$ and the other probably $f_0(1370)$. This scheme might shed more light on why extra states could appear in the hadron spectrum other than the prediction of the quark potential model.

hep-ph↗

Relationships among quasivarieties induced by the min networks on inverse semigroups

A congruence on an inverse semigroup $S$ is determined uniquely by its kernel and trace. Denoting by $ρ_k$ and $ρ_t$ the least congruence on $S$ having the same kernel and the same trace as $ρ$, respectively, and denoting by $ω$ the universal congruence on $S$, we consider the sequence $ω$, $ω_k$, $ω_t$, $(ω_k)_t$, $(ω_t)_k$, $((ω_k)_t)_k$, $((ω_t)_k)_t$, $\cdots$. The quotients $\{S/ω_k\}$, $\{S/ω_t\}$, $\{S/(ω_k)_t\}$, $\{S/(ω_t)_k\}$, $\{S/((ω_k)_t)_k\}$, $\{S/((ω_t)_k)_t\}$, $\cdots$, as $S$ runs over all inverse semigroups, form quasivarieties. This article explores the relationships among these quasivarieties.

math.GR↗

QCD sum rule studies on the $s s \bar s \bar s$ tetraquark states of $J^{PC} = 0^{-+}$

We apply the method of QCD sum rules to study the $s s \bar s \bar s$ tetraquark states of $J^{PC} = 0^{-+}$. We construct all the relevant $s s \bar s \bar s$ tetraquark currents, and find that there are only two independent ones. We use them to further construct two weakly-correlated mixed currents. One of them leads to reliable QCD sum rule results and the mass is extracted to be $2.51^{+0.15}_{-0.12}$ GeV, suggesting that the $X(2370)$ or the $X(2500)$ can be explained as the $ss\bar s\bar s$ tetraquark state of $J^{PC} = 0^{-+}$. To verify this interpretation, we propose to further study the $ππ/K \bar K$ invariant mass spectra of the $J/ψ\to γππη^\prime/γK \bar K η^\prime$ decays in BESIII to examine whether there exists the $f_0(980)$ resonance.

hep-ph↗

Decays of $X(3872)$ to $χ_{cJ}π^0$ and $J/ψπ^+π^-$

By describing the $X(3872)$ using the extended Friedrichs scheme, in which $D\bar D^*$ is the dominant component, we calculate the decay rates of the $X(3872)$ to $π^0$ and a $P$-wave charmonium $χ_{cJ}$ state with $J=0,1$, or $2$, and its decays to $J/ψπ^+π^-$ where $π^+π^-$ are assumed to be produced via an intermediate $ρ$ state. The decay widths of $X(3872)\toχ_{cJ}π^0$ for $J=0,1,2$ are of the same order. However, this model calculation exhibits that the decay rate of $X(3872)$ to $χ_{c1}π^0$ is one order of magnitude smaller than its decay rate to $J/ψπ^+π^-$.

hep-ph↗