SearcharxivSearch

arXiv subjects

Xin-Heng Guo

Publications and source records attributed to Xin-Heng Guo.

At least 19 recordsLinked to original sources

Possible Bound States in the $D^\ast\bar D^\ast$/$B^\ast\bar B^\ast$ and $D^\ast D^\ast$/$\bar B^\ast\bar B^\ast$ Systems within the Bethe-Salpeter Formalism

We investigate possible $S$-wave bound states in the $D^\ast\bar D^\ast$, $B^\ast\bar B^\ast$, $D^\ast D^\ast$, and $\bar B^\ast\bar B^\ast$ systems within the Bethe-Salpeter formalism using one-boson-exchange interactions. Bound state solutions are obtained in the isoscalar hidden-heavy systems with $J^{PC}=0^{++}$, $1^{+-}$, and $2^{++}$, whereas no isovector solutions are found within the parameter range considered. For the doubly heavy systems, solutions are obtained in the allowed $I(J^P)=0(1^+)$, $1(0^+)$, and $1(2^+)$ systems, although the $1(0^+)$ solution requires a comparatively large cutoff parameter. The bottom systems are bounded more favorably than their charmed counterparts because of their larger reduced masses.

hep-ph

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

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

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

Direct $CP$ violation in $D^\pm \to π^\pm π^+ π^-$ with $a_0^0(980)-f_0(980)$ mixing

We investigate the direct $CP$ violation in the decay $D^\pm \to π^\pm π^+ π^-$ incorporating the $a_0^0(980)$-$f_0(980)$ mixing mechanism. The integrated mixing intensities $\overline ξ_{fa}$ and $\overline ξ_{af}$ are calculated using meson masses and coupling constants extracted from various theoretical models and experimental data, yielding values of appreciable magnitude. We find that when the invariant mass of the $π^+π^-$pair lies near the $f_0(980)$ resonance, this isospin breaking mechanism can enhance the $CP$ asymmetry. The enhancement is particularly pronounced when $f_0(980)$ carries a significant $n\bar{n}$ quark component and the $f_0(980)$ and $σ(600)$ mixing angle is approximately $26^\circ$. It is emphasized that the $a_0^0(980)$-$f_0(980)$ mixing mechanism can be taken into account in both theoretical and experimental studies of $CP$ violation in $B$ or $D$ meson decays.

hep-ph

The properties of the $S$-wave $D_s\bar{D}_s$ bound state

In this work, we investigate possible bound states of the $D_s\bar{D}_s$ system in the Bethe-Salpeter formalism in the ladder and instantaneous approximations. By numerically solving the Bethe-Salpeter equation with a kernel that includes the contributions from $ϕ$ and $J/ψ$ exchanges, we confirm the existence of a bound state in the $D_s\bar{D}_s$ system. We further investigate the partial decay widths of the $D_s\bar{D}_s$ bound state into $D\bar{D}$, $η_cη$, and $J/ψω$, finding that these partial widths are sensitive to the parameter $α$ in our model. Notably, we observe that the dominant decay channel for the $D_s\bar{D}_s$ bound state is that into $D\bar{D}$.

hep-ph

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

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

Study of $Kπ$ final states from four-body deacy of $\bar{B}_{s}$ meason under perturbation QCD

In the perturbative QCD framework, we use the quasi-two-body method to study the CP violations and branching ratios in the $\bar B_{s} \rightarrow [ϕ(ρ^{0},ω)\rightarrow K^{+}K^{-}][K^{*0}\rightarrow K^{+}π^{-}]$ and $\bar B_{s} \rightarrow [ρ^{0}(ω,ϕ)\rightarrow (π^{+}π^{-})][K^{*0}\rightarrow K^{+}π^{-}]$ decay processes. Owing to the interference effects of $ρ^{0}$, $ω$, and $ϕ$, new strong phases associated with vector mesons will be generated, resulting in relatively large CP violation within the interference region. Moreover, we provide numerical comparisons of CP violation from resonance effects and non-resonance contributions. In order to provide better theoretical predictions for future experiments, we integrate CP violation over invariant mass to obtain the regional CP violation value. Furthermore, we have calculated the polarization fractions and branching ratios for different intermediate states in the four-body decay process, which may be influenced by vector interference effects. Additionally, we discuss the possibility of observing the predicted CP violation at the LHC.

hep-ph

Nature of X(3872) from recent BESIII data: Considering the universal feature of an S-wave threshold resonance

We analyze the recent data from the BESIII collaboration on the $X(3872)$ state in the $J/ψπ^+π^-$ and $D^0\bar{D}^0π^0$ decay channels. The quantum number and mass of the $X(3872)$ state allow us to exploit the universal feature of the very near-threshold $D\bar D^*$ scattering in the $S$ wave. The analysis of $J/ψπ^+π^-$ data and $D^0\bar{D}^0π^0$ data separately as well as the combined analysis of these data together, all support the conclusion that $X(3872)$ is an extremely weakly bound charm meson molecule.

hep-ph

The $CP$ violations and branching ratios for $B_c^+\to D_{(s)}^+π^+π^-(K^{+}K^{-})$ from interference of the vector mesons in Perturbative QCD

Within the framework of the perturbative QCD approach utilizing $K_T$ factorization, we have investigated the CP violations and branching ratios in the decay processes of $B_{c}^{+}\to D_{(s)} ^{+}V(V\rightarrowπ^{+}π^{-})$ and $B_{c}^{+}\to D_{(s)}^{+}V(V\rightarrow K^{+}K^{-})$, where V denotes three vector mesons $ρ^0$, $ω$, and $ϕ$. During the $V\to π^+π^-$ and $V\to K^+K^-$ decay processes, we incorporated the $ρ^{0}-ω-ϕ$ mixing mechanism to describe the amplitudes of these quasi-two-body decay processes. Within the interference regime of the three vector particles, we observed distinct changes in both CP violations and branching ratios. Furthermore, our study presents evidence for local CP violations and branching ratios that warrants further investigation through experiments.

hep-ph

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

CP asymmetry from the effect of the isospin symmetry breaking during B-meson decay

The direct CP asymmetry in quasi-two-body decays of $B \rightarrow (V\rightarrow π^{+}π^{-})P $ is investigated in the perturbative QCD method, where P represents a pseudoscalar meson and V refers to $ρ$, $ω$ and $ϕ$ mesons, respectively. We present the amplitude of the quasi-two-body decay process and investigate the effects of mixed resonances involving $ρ^{0}-ω$, $ρ^{0}-ϕ$ and $ω-ϕ$, while considering the impact of isospin symmetry breaking. We observe a significant CP asymmetry when the invariant mass of the $π^{+}π^{-}$ pair is within the resonance ranges of $ρ$, $ω$ and $ϕ$ mesons. Consequently, we proceed to quantify the regional CP asymmetry in these resonance regions. A significant difference is observed when comparing results obtained with and without interferences of the three vector mesons and isospin conservation. The CP asymmetry results obtained from the three-body decay process, without interference due to isospin conservation by the perturbative QCD method, are in agreement with the newly updated data acquired by the LHCb experiment.

hep-ph

Possible bound states of Heavy Baryonium and Heavy Dibaryon systems

In this work, we systematically study the heavy baryonium and heavy dibaryon systems using the Bethe-Salpeter equation in the ladder and instantaneous approximations for the kernel. Our results indicate that all the heavy baryonium systems, specifically $Λ_Q\barΛ_Q$, $Ξ_Q\barΞ_Q$, $Σ_Q\barΣ_Q$, $Ξ'_Q\barΞ'_Q$, and $Ω_Q\barΩ_Q$ ($Q=c, b$), can form bound states. Among the heavy dibaryon systems, only the $Ξ_QΞ_Q$ system with $I=0$ and the $Σ_QΣ_Q$ systems with $I=0$ and $I=1$ can exist as bound states. Additionally, the $Σ_Q\barΣ_Q$ system with $I=2$ and the $Σ_QΣ_Q$ system with $I=1$ are not deeply bound.

hep-ph

The masses and decay widths of the $S$-wave $Λ_c\barΛ_c$ bound states

In this work, we investigate possible bound states of the $Λ_c\barΛ_c$ system in the Bethe-Salpeter formalism in the ladder and instantaneous approximations. By numerically solving the Bethe-Salpeter equation, we confirm the existence of $Λ_c\barΛ_c$ bound states with quantum numbers $J^{PC}=0^{-+}$ and $J^{PC}=1^{--}$. We further investigate the partial decay widths of the $Λ_c\barΛ_c$ bound states into $N\bar{N}$, $D\bar{D}$, $D\bar{D}^\ast$, $D^\ast\bar{D}^\ast$, $π\barπ$, and $K\bar{K}$. Our results indicate that the decay width of the $Λ_c\barΛ_c$ bound state with $J^{PC}=1^{--}$ is much larger than that with $J^{PC}=0^{-+}$, and among their decay channels, the $D\bar{D}^\ast$ final state is the main decay mode. We suggest experiments to search for the $Λ_c\barΛ_c$ bound states in the $D\bar{D}^\ast$ final state.

hep-ph

Decay-angular-distribution correlated $CP$ violation in heavy hadron cascade decays

$C\!P$ violation in baryon decay processes is still undiscovered to date. We present a general analysis of the decay-angular-distributions and the corresponding $C\!P$ asymmetries in cascade decays of the type $\mathbb{H}\to R(\to ab) c$, where $\mathbb{H}$ is a heavy hadron that decays through weak interactions $\mathbb{H}\to R c$, and the resonance $R$ decays strongly via $R\to ab$. Based on the analysis, we propose to search for $C\!P$ violation in the decay-angular-distributions in the cascade decay processes ${\mathbb{B}}\to \mathcal{B} M$, with $\mathcal{B}$ or $M$ subsequently decaying through strong interactions, where ${\mathbb{B}}$ is the mother baryon, $\mathcal{B}$ or $M$ are the daughter baryon and meson, respectively, and $M$ has to be spin-nonzero. We also present some typical decay channels in which the search for such kinds of $C\!P$ asymmetries can be performed.

hep-ph

CP asymmetry from resonance effect of B meson decay process with $π$ and K final states

We introduce the new resonance of $V\rightarrow K^{+}K^{-}$ $(V=ϕ, ρ, ω)$, which produces some new strong phase associated with vector meson resonance and thus can cause relatively large CP asymmetry at the range of interferences. There are the resonances of $ϕ\rightarrow K^{+}K^{-}$, $ρ\rightarrow K^{+}K^{-}$ and $ω\rightarrow K^{+}K^{-}$ due to the mixing of vector mesons $ϕ$, $ρ$, $ω$. We calculate the CP asymmetry from the decay modes of $B \rightarrow KKπ(K)$. Meanwhile, the localised CP asymmetries are presented and some detailed analysis can be found. The CP asymmetry from the decay mode of ${B}^{-}\rightarrow ϕπ^{-}\rightarrow K^{+}K^{-}π^{-}$ is also presented in our framework which is well consisted with LHC experiment. The introduced CP asymmetry can provide a favorable theoretical support for the experimental exploration in the future.

hep-ph

Analysis of localized CP asymmetry in $\bar{B}_{s}^{0} \rightarrow π^+π^-π^{0}(K^{0})$

An investigation about localized CP asymmetries for the processes of $\bar{B}_{s}^{0} \rightarrow π^{+}π^{-}π^{0} (K^{0})$ is presented in this paper. The innovation of this paper is that there is a consideration of three-particle $ρ^0(770)$, $ω(782)$ and $ϕ(1020)$ interferences effect. Generally, $ω(782)$ and $ϕ(1020)$ both can decay into $π^+π^-$ pair where can cause extremely small contribution from isospin symmetry breaking. Nevertheless, our analysis shows that $\bar{B}_{s}^{0} \rightarrow π^+π^-π^{0}(K^{0})$ decay process can bring differential CP asymmetry about $65\%$ ($36\%$) because of isospin symmetry breaking. To better compared with the data from experimental in the future, we integrate CP asymmetry over the invariant mass and obtain localized CP asymmetry value for the decay $\bar{B}_{s}^{0} \rightarrow π^+π^-π^{0} (K^{0})$. We find that there is an evident signal about CP asymmetry at invariant mass value $m(π^{+}π^{-})$ below the mass of $ρ(770)^{0}$ with the decay $\bar{B}_{s}^{0} \rightarrow π^+π^{-}π^{0}$.

hep-ph