arXiv subjects

Zhi-Qing Zhang

Publications and source records attributed to Zhi-Qing Zhang.

At least 19 recordsLinked to original sources

arXiv2026

The $Υ(nS) \to B_{(c)}$ transition form factors and their applications to semileptonic and nonleptonic weak decays

The semileptonic and nonleptonic decays of the $Υ(nS)$ with $n=1,2,3,4$ are investigated within the covariant light-front quark model (CLFQM). Using the form factors of the transitions $Υ(nS) \to B_{(c)}$ obtained from the CLFQM, we calculate the branching ratios of the decays $Υ(nS)\to B_{(c)}\ellν_\ell$ and $Υ(nS)\to B_{(c)}M$ with $\ell=e,μ,τ$ and $M$ referring to $π(ρ),K^{(*)},D^{(*)},D^{(*)}_s$. One can find that the branching ratios of the decays $Υ(3S)\to B_c\ellν_\ell$ are the largest among those of considered semileptonic decays and can amount to $10^{-9}$; As to the nonleptonic decays, $Υ(3S)\to B_cρ$ and $Υ(3S)\to B_cD^{(*)}_s$ have the largest branching ratios, which reach up to $10^{-10}$. Given the identification and detection efficiency of final states, searching for these weak decay modes should be fairly challenging in future experiments. The forward-backward asymmetry $A_{FB}$ and the longitudinal polarization fraction $f_L$ are also calculated for those semileptonic decays.

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arXiv2026

Semi-leptonic decays $B \to D^{(*)}(1S,2S)\ell ν_{\ell}$ within the covariant light-front approach

We present a systematic analysis of the semi-leptonic decays $B_{(s)}\to D_{(s)}(1S,2S)\ellν_\ell$ and $B_{(s)}\to D^*_{(s)}(1S,2S)\ellν_\ell$ with $\ell=e,μ,τ$ within the covariant light-front quark model (CLFQM). Using the form factors of the transitions $B_{(s)}\to D_{(s)}(1S,2S)$ and $B_{(s)}\to D^*_{(s)}(1S,2S)$, we calculate the branching ratios of the relevant semi-leptonic decays and find that $Br(B_{(s)}\to D_{(s)}\ell^\primeν_{\ell^\prime})$ and $Br(B_{(s)}\to D^*_{(s)}\ell^\primeν_{\ell^\prime})$ with $\ell^\prime=e,μ$ are agree well with the data, while $Br(B_{(s)}\to D_{(s)}τν_τ)$ and $Br(B_{(s)}\to D^*_{(s)}τν_τ)$ are systematically smaller than the experimental measurements. This naturally gives rise to the so-called $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$ anomalies. Our predictions $\mathcal{R}(D)=0.261\pm0.013$ and $\mathcal{R}(D^*)=0.228\pm0.026$ show $3.1σ$ and $2.1σ$ deviations from the current experimental world averages compiled by the Heavy Flavor Averaging Group (HFLAV), respectively, yet only deviate by $0.16σ$ and $1.5σ$ from the latest LHCb measurements. For the decays $B_{(s)}\to D_{(s)}(2S)\ellν_\ell$ and $B_{(s)}\to D^*_{(s)}(2S)\ellν_\ell$, their branching ratios lie in the range $10^{-4}\sim10^{-3}$, which are much larger than the results from the Bethe Salpeter (BS) equation , but agree with the relativistic quark model (RQM) calculations. Furthermore, we also calculate the forward-backward asymmetries $\mathcal{A}_{FB}$ and longitudinal polarization fractions $f_L$ for the corresponding decays. Our predictions are consistent with most other theoretical results and experimental data

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arXiv2026

Semi-leptonic $B$ decays to tensor mesons

Using the form factors of the transtions $B\to T$ with $T$ refering to a tensor meson, such as $a_2(1320), f_2(1270),K^*_2(1430), D_2^*(2460)$ and $D^*_{2s}(2573)$, within the covariant light-front quark model (CLFQM), we provide a detailed investigation of the corresponding semi-leptonic decays $B\to T\ellν_\ell$ with $\ell=e,ν,τ$. All the branching ratios of these decays are larger than $10^{-5}$, in which the maximum value can reach up to $10^{-3}$, indicating promising prospects for experimental observation. Furthermore, we also calculate the longitudinal polarization fractions $f_L$ and forward-backward asymmetries $A_{FB}$ for these considered decays. All the decays $B\to T \ellν_{\ell}$ are dominated by the longitudinal polarization, where the polarization fractions can reach up to $\sim70\%$ for the decays $B\to T \ell^{\prime}ν_{\ell^\prime}$ with $\ell^\prime=e, μ$, those of the decays $B\to T τν_τ$ are a little smaller. The $A_{FB}$ values of the decays $B\to T \ell^{\prime}ν_{\ell^\prime}$ and $B\to T τν_τ$ have opposite signs.

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arXiv2026

$D_{(s)}(2S)$ and $D^{*}_{(s)}(2S)$ production in nonleptonic $B_{(s)}$ weak decays

Recently, many new excited states of heavy mesons have been discovered in recent experiments, including radially excited states. The production processes of these states from the $B_{(s)}$ meson have drawn significant interest. In this paper, we use the covariant light-front approach to study the nonleptonic $B_{(s)}$ meson decays to the first radially excited states $D_{(s)}(2S)$ and $D^{*}_{(s)}(2S)$. Our results reveal that many channels exhibit large branching ratios in the range $10^{-5}\sim 10^{-4}$, even up to $10^{-3}$ for individual channels, which are detectable by current experiments. Our predictions for the decays $B_{(s)}\to D^{(*)}_{(s)}(2S)(π,ρ,K^{(*)})$ are larger than those given by the Bethe-Salpeter (BS) equation method, but agree well with the relativistic quark mode (RQM) and the relativistic independent quark model (RIQM) calculations. For comparison, we also present the branching ratios of the decays $B_{(s)}\to D^{(*)}_{(s)}(1S)(π,ρ,K^{(*)})$, which are comparable with other theoretical results and the data. Although the branching ratios of the decays $B_{(s)} \to D^{*}_{(s)}(1S)(ρ,K^*)$ are much larger than those of the decays $B_{(s)} \to D^{*}_{(s)}(2S)(ρ,K^*)$, the polarization properties between them are similar, that is, the longitudinal polarization fractions are dominant and can amount roughly to $90\%$.

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arXiv2026

Systematic analysis of $D_{(s)}$ meson semi-leptonic decays in the covariant light-front quark model

The weak decays of the $D_{(s)}$ meson provide a pivotal platform to advance our understanding of the Standard Model (SM) and to explore New Physics (NP). In recent years, experiments have collected a significant amount of data on the $D_{(s)}$ meson decays, particularly from BESIII, which provides substantial support for theoretical research. In this work, we systematically investigate the semi-leptonic decays of $D_{(s)}$ meson to pseudoscalar (P), scalar (S), vector (V), and axial-vector (A) mesons within the framework of the covariant light-front quark model (CLFQM). We calculate the form factors of the transitions $D_{(s)}\to P,S,V,A$ and the branching ratios of the corresponding semi-leptonic decays, then compare them with experimental data and results from other theoretical models. The form factor values of the transitions $D_{(s)}\to P, V$ obtained from the CLFQM are consistent with those of other theoretical models and available data in most cases. However, significant discrepancies are found in some specific $D_{(s)}\to S,A$ transitions, such as $D\to a_0(980), a_0(1450)$ and $D_{(s)} \to K_{1B}$, compared to other theoretical calculations. The predicted branching ratios for the semi-leptonic decays $D\to P(V)\ellν_\ell$ with $\ell=e,μ$ agree well with experimental data and other theoretical results in most decay channels, validating the reliability of the model. However, for some $D\to S(V)\ellν_\ell$ decays, tension exists among different theoretical predictions and experimental results. Further clarification of such differences is necessary. Our study provides important insights into the internal structures for some scalar and axial-vector mesons and serves as a theoretical reference for future experiments.

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arXiv2026

$D^*_{(s)}\to P$ form factors and their applications to semi-leptonic and non-leptonic weak decays

Similar to other heavy flavor mesons, the weak decays of $D^*_{(s)}$ mesons can provide a platform to verify the standard model, explore new physics, and understand the mechanisms of weak interactions. At present, the theoretical and experimental studies on $D^*_{(s)}$ mesons are relatively limited. In addition to the dominant electromagnetic decays, the $D^*_{(s)}$ weak decays should be feasible to explore the $D^*_{(s)}$ mesons. In this study, we used the covariant light-front quark model to study the form factors of the transitions $D^*_{(s)}\to π, K, η_{q,s}$, then calculated the branching ratios of the semi-leptonic decays $D^*_{(s)}\to P\ell^{+}ν_{\ell}$ and the non-leptonic decays $D^*_{(s)}\to PP, PV$ with $P=π, K, η^{(\prime)}, V=ρ, K^*, ϕ$ and $\ell=e, μ$. The channels $D_{s}^{*+}\toη\ell^{+}ν_{\ell}$ and $D^{*+}_{s}\to ηρ^{+}$ possess the largest branching ratios, which can reach an order of $10^{-6}$ among these decays, and are most likely to be accessible in experiments at future high-luminosity colliders. Furthermore, we predict and discuss the longitudinal polarization fraction $f_{L}$ and the forward-backward asymmetry $A_{FB}$ for the considered semi-leptonic $D^*_{(s)}$ decays.

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arXiv2025

Semileptonic $B_{(s)}$ meson decays to $D_{0}^{\ast}(2300) ,D_{s0}^{\ast}(2317) , D_{s1}(2460), D_{s1}(2536), D_{1}(2420)$ and $D_{1}(2430)$ within the covariant light-front approach

In this work, we investigate the semileptonic decays of $B_{(s)}$ meson to $D_{0}^{\ast}(2300)$, $D_{s0}^{\ast}(2317)$, $D_{s1}(2460)$, $D_{s1}(2536)$, $D_{1}(2420)$ and $D_{1}(2430)$ in the covariant light-front quark model (CLFQM). We combine the helicity amplitudes via the corresponding form factors to obtain the branching ratios of the semileptonic decays $B_{(s)} \to D^{**}_{(s)}\ell ν_\ell$ with $D^{**}_{(s)}$ referring to a P-wave exicted charmed meson $D_{0}^{\ast}(2300)$, $D_{s0}^{\ast}(2317)$, $D_{s1}(2460)$, $D_{s1}(2536)$, $D_{1}(2420)$ or $D_{1}(2430)$ and $\ell=e, μ, τ$. Furthermore, we also take into account another two physical observables, namely the longitudinal polarization fraction $f_L$ and the forward-backward asymmetry $A_{FB}$. Most of our predictions are comparable to the results given by other theoretical approaches and the present available data. The branching ratios of the semileptonic decay channels $B_{s} \to D_{s1}(2460) \ell ν_\ell$ and $B \to D_{1}(2420) \ell ν_\ell$ are larger than those of the semileptonic decays $B_{s} \to D_{s1}(2536) \ell ν_\ell$ and $B \to D_{1}(2430) \ell ν_\ell$, respectively. We find that the long-standing '$1/2$ vs $3/2$ puzzle' in the decays $B^{+}\to \bar{D}_1^{(\prime)0} \ell^{\prime+}ν_{\ell^\prime}$ $(\ell^\prime=e,μ)$ can be solved by taking some negative mixing angle $θ_s$ values within a range from $-30.3^\circ$ to $-24.9^\circ$, corresponding to $θ$ of about $5^\circ\sim10.4^\circ$. While Belle collaboration updated their measurements for the decays $B^{0}\to D^{*-}_0 \ell^{\prime+}ν_{\ell^\prime}$ with only a small upper limit $Br(B^{0}\to D^{*-}_0 \ell^{\prime+}ν_{\ell^\prime})<0.44\times10^{-3}$ obtained, which is much larger than most theoretical predictions and causes a new puzzle.

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arXiv2024

$B\to K\bar K(πη)h$ decays in the presence of isovector scalar resonances $a_0(980,1450)$

Different from the previous treatment in a two-body framework, we introduce the dimeson distribution amplitudes (DAs) to describe the strong dynamics between the S-wave resonances $a_0(980, 1450)$ and the $K\bar K (πη)$ pair, where the Gegenbauer coefficient required is determined from the experimental data on the time-like form factors involved. The branching ratios and direct CP asymmetries of the decays $B \to a^{(\prime)}_0 h \to K\bar K(πη) h$, with $a_0=a_0(980)$, $a^{\prime}_0=a_0(1450)$ and $h$ referring to a pion or a kaon, are then calculated in the perturbative QCD (PQCD) approach. We find that the branching ratios of the corresponding quasi-two-body decays $B\to a^{(\prime)}_0 K$ obtained with the narrow width approximation are closer to those predicted in the QCD factorization (QCDF) approach compared to the previous PQCD calculations, no matter a three-body or a two-body framework is assumed. Furthermore, all our predictions for these $B\to a^{(\prime)}_0 K$ decays are below the current experimental upper limits except for those of decays $B^0\to a^{(\prime)-}_0K^+$, which are (slightly) larger than the upper limits. Under the narrow width approximation, the branching ratios of the decays $B^+\to a^{(\prime)+}_0π^0$, $B^0\to a^{(\prime)+}_0π^-$ and $B^0\to a^{(\prime)0}_0π^0$ are comparable to or agree well with the previous PQCD and the QCDF calculations. While for the decays $B^+\to a^{(\prime)0}_0π^+$ and $B^0\to a^{(\prime)-}_0π^+$, their branching ratios are predicted to be unexpectedly large, for example, the obtained branching ratio of decay $B^+\to a^0_0π^+$ is even higher than the current experimental upper limit.

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arXiv2024

Semileptonic $B_{c}$ meson decays to S-wave charmonia and $X(3872)$ within the covariant light-front approach

In this work, we investigate the semileptonic decays of $B_{c}$ meson to $η_{c}(1S,2S,3S)$, $ψ(1S,2S,3S)$ and $X(3872)$ within the framework of covariant light-front quark model (CLFQM). We combine the helicity amplitudes via the corresponding form factors to obtain the branching ratios of the semileptonic decays $B_{c}\to η_{c}(1S, 2S, 3S)\ellν_{\ell}$, $B_{c}\to ψ(1S, 2S, 3S))\ellν_{\ell}$ and $B_{c}\to X(3872)\ellν_{\ell}$ with $\ell=e,μ,τ$. In view of the $R_{J/Ψ}$ anomaly released by the LHCb collaboration, it is necessary to calculate the ratios $R_X$ with $X=ψ(1S,2S,3S),η_c(1S,2S,3S),X(3872)$ systematically, which are helpful to check the lepton flavor universality (LFU). Furthermore, we also take into account another two physical observables, one is the longitudinal polarization fraction $f_{L}$ and the other is the forward-backward asymmetry $A_{FB}$, which can provide new clues to understand the $R_{J /Ψ}$ anomaly. Such theoretical predictions are necessary and interesting, which can be tested in the future LHCb experiments.

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arXiv2024

Semileptonic and nonleptonic weak decays of $ψ(1S,2S)$ and $η_{c}(1S,2S)$ to $D_{(s)}$ in the covariant light-front approach

In addition to the strong and electromagnetic decay modes, the $ψ(1S,2S)$ and $η_{c}(1S,2S)$ can also decay via the weak interaction. Such weak decays can be detected by the high-luminosity heavy-flavor experiments. At present, some of the semileptonic and nonleptonic $J/Ψ$ weak decays have been measured at BESIII. Researching for these charmonium weak decays to $D_{(s)}$ meson can provide a platform to check of the standard model (SM) and probe new physics (NP). So we investigate the semileptonic and nonleptonic weak decays of $ψ(1S,2S)$ and $η_{c}(1S,2S)$ to $D_{(s)}$ within the covariant light-front quark model (CLFQM). With form factors of the transitions $ψ(1S,2S)\to D_{(s)}$ and $η_{c}(1S,2S)\to D_{(s)}$ calculated under the CLFQM, we predict and discuss some physical observables, such as the branching ratios, the longitudinal polarizations $f_{L}$ and the forward-backward asymmetries $A_{FB}$. One can find that the Cabibbo-favored semi-leptonic decay channels $ψ(1S,2S)\to D_{s}^{-}\ell^{+}ν_{\ell}$ with $\ell=e,μ$ and the nonleptonic decay modes $ψ(1S,2S)\to D_{s}^{-}ρ^{+}$ have relatively large branching ratios of the order $\mathcal{O}(10^{-9})$, which are most likely to be accessible at the future high-luminosity experiments.

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arXiv2024

Semileptonic and nonleptonic decays of $B_{u,d,s,c}^{*}$ in the covariant light-front approach

The semileptonic and nonleptonic decays of the b-flavor vector mesons $B^{*}_{u,d,s}$ and $B_{c}^{*}$ are investigated within the covariant light-front quark model (CLFQM). By calculating the form factors of the transitions $B_{u, d, s, c}^{*}\to P$ under the CLFQM, with $P$ denoting a pseudoscalar meson, i.e., $π, K, η_c(1S,2S), D_{(s)}, B_{(s)}$, we predict and discuss several physical observables, including the branching ratios, polarization fractions $f_{L}, f_{\|}$, and forward-backward asymmetries $A_{FB}$. The total widths of the single-photon radiative decay channels for these b-flavor vector mesons are estimated using their partial widths. In these considered decays, one can find that the semileptonic decays $B_{s}^{*0}\to D_{s}^{-}\ell^{\prime+}ν_{\ell^\prime}$ and $B_{c}^{*+}\to B_{s}^{0}\ell^{\prime+}ν_{\ell^\prime}, η_{c}\ell^{\prime+}ν_{\ell^\prime}$, with $\ell^\prime$ being $e$ or $τ$, and the nonleptonic channels $B_{c}^{*+}\to B^0_{s} π^{+}, B^0_{s} ρ^{+}$ have the largest branching ratios, which can reach up to the $10^{-7}$ order, and are most likely to be accessible at the future high-luminosity LHCb and Belle-II experiments.

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arXiv2024

Branching ratios and CP asymmetries of the quasi-two-body decays $B_c \rightarrow \ K^{*}_0(1430,1950) D_{(s)} \rightarrow K πD_{(s)} $ in the PQCD approach

In this paper, we investigate the quasi-two-body decays $B_c \to K_0^{*}(1430,1950) D_{(s)} \to K πD_{(s)}$ within the perterbative QCD (PQCD) framework. The S-wave two-meson distribution amplitudes (DAs) are introduced to describe the final state interactions of the $Kπ$ pair, which involve the time-like form factors and the Gegenbauer polynomials. In the calculations, we adopt two kinds of parameterization schemes to describe the time-like form factors: One is the relativistic Breit-Wigner (RBW) formula, which is usually more siutable for the narrow resonances, and the other is the LASS line shape proposed by the LASS Collaboration, which includes both the resonant and nonresonant components. We find that the branching ratios and the direct CP violations for the decays $B_c \to K_0^{*}(1430) D_{(s)}$ obtained from those of the quasi-two-body decays $B_c \to K_0^{*}(1430) D_{(s)} \to K πD_{(s)}$ under the narrow width approximation (NWA) can be consistent well with the previous PQCD results calculated in the two-body framework by assuming that $K^*_0(1430)$ being the lowest lying $\bar q s$ state, which is so-called scenario II (SII). We conclude that the LASS parameterization is more siutable to describe the $K_0^{*}(1430)$ than the RBW formula, and the nonresonant components play an important role in the branching ratios of the decays $B_c \to K_0^{*}(1430) D_{(s)} \to K πD_{(s)}$. In view of the large difference between the decay width measurements for the $K_0^{*}(1950)$ given by BaBar and LASS collaborations, we calculate the branching ratios and the CP violations for the quasi-two-body decays $B_c \to K_0^{*}(1950) D_{(s)} \to K πD_{(s)}$ by using two values, $Γ_{K^*_0(1950)}=0.100\pm0.04$ GeV and $Γ_{K^*_0(1950)}=0.201\pm0.034$ GeV, besides the two kinds of parameterizations for the resonance $K^*_0(1950)$.

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arXiv2024

Study of $B_{(s)}$ meson decays to $D_{0}^{\ast}(2300) ,D_{s0}^{\ast}(2317) , D_{s1}(2460)$ and $D_{s1}(2536)$ within the covariant light-front approach

In this work, we investigate the form factors of the transitions $B_{(s)} \to D_{0}^{\ast}(2300),D_{s0}^{\ast}(2317),$ $ D_{s1}(2460) $ and $ D_{s1}(2536)$ in the covariant light-front quark model (CLFQM), where these final states are considered as P-wave excited charmed mesons. In order to obtain the form factors for the physical transition processes, we need to extend these form factors from the space-like region to the time-like region. The $q^{2}$-dependence for each transition form factor is also plotted. Then, combined with those form factors, the branching ratios of the two-body nonleptonic decays $B_{(s)}\to D^*_{(s)0}(2300,2317)M, D_{s1}(2460,2536)M$ with $M$ being a light pseudoscalar (vector) meson or a charmed meson are calculated by considering the QCD radiative corrections to the hadronic matrix elements with the QCD factorization approach. Most of our predictions are comparable to the results given by other theoretical approaches and the present available data.

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arXiv2023

Covariant Light-Front Approach for $B_c$ Decays into Charmonium: Implications on Form Factors and Branching Ratios

In this work, we investigate the form factors of $B_c$ decays into $J/Ψ, ψ(2S,3S)$, $η_c, η_c(2S,3S), χ_{c0}, χ_{c1}, h_c$ and $X(3872)$ mesons in the covariant light-front quark model (CLFQM). For the purpose of the branching ratio calculation, the form factors of $B_c\to D^{(*)}, D^{(*)}_s$ transitions are also included. In order to obtain the form factors for the physical transition processes, we need extend these form factors from the space-like region to the time-like region. The $q^2$-dependence for each transition form factor is also plotted. Then, under the factorization method, we calculate the branching ratios of 80 $B_c$ decay channels with a charmonium involved in each mode. Most of our predictions are comparable with the results given by most of other approaches. As to the decays with the radially excited state S-wave charmonia, such as $ψ(2S,3S)$ and $η_c(2S,3S)$, involved, there are two sets of parameters for their light-front wave functions, corresponding to scenario I (SI) and scenario II (SII), are adopted to calculate the branching ratios. Comparing with the future experimental data, one can discriminate which parameters are more favored.

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arXiv2023

Quasi-two-body decays $B_c \to K^{*} h \to K πh $ in the perturbative QCD

In this work we study the quasi-two-body decays $B_c \to \ K^{*} h \to K πh (h = D, D_s, K, π, η, η')$ in the perturbative QCD (PQCD) approach. The two-meson distribution amplitudes (DAs) $Φ^{\text{P-wave}}_{Kπ}$ are introduced to describe the final state interactions of the K πpair, which involve the time-like form factors F_{Kπ}(s) parameterized by the relativistic Breit-Wigner function and the Gegenbauer polynomials. We calculate the branching ratios for these quasi-two-body decays, from which one can obtain the branching raios for the corresponding two-body decays under the narrow width approximation relation. We find that $B^+_c\to K^{*+}D^0$ and $B^+_c\to K^{*0}D^+$ have the largest branching ratios, which can reach up to $10^{-6}$, while the branching ratios for other two-body decays are very small and only about $10^{-8}\sim10^{-7}$. As we expected that the branching ratios of the pure annihilation decays are usually small, while in our considered such type of decays, the channel $B_c^+ \to \bar K^{*0}K^{+}$ has the largest branching ratio, which is near $10^{-6}$. These results are consistent with the previously PQCD calculations obtained in the two-body framework, which can be tested by the future LHCb experiments. For the decays $B_c^+ \to K^{*+} D^{0}\to K^{0}π^+D^{0} , B_c^+ \to K^{*0}D^{+}\to K^{+}π^-D^{+}$ and $B_c^+ \to \bar K^{*0}D_s^{+}\to K^{-}π^+D_s^{+}$, we calculate their direct CP violations and find that $A_{CP}(B_c^+ \to K^{*+}D^{0}\to K^{0}π^+D^{0})=(-14.6_{-1.12}^{+9.19})\%$ is the largest one, which is possible measured by the present LHCb experiments. For the pure annihilation type decays, there is no CP violations because only the tree operators are involved. Furthermore, we also give the differential distributions of the branching ratios and the direct CP violations for the decays $B_c\to K^* D_{(s)}\to K πD_{(s)}$.

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arXiv2023

Quasi-two-body decays $B_c\to D^*h\to Dπh$ in the perturbative QCD

In this work, we investigate the quasi-two-body decays $B_c\to D^*h\to Dπh$ with $h = (K^0,π^0,η,η^{\prime})$ using the perturbative QCD(PQCD) approach. The description of final state interactions between the $Dπ$ pair is achieved through the two-meson distribution amplitudes(DAs), which are normalized to the time-like form factor. The PQCD predictions on the branching ratios of the quasi-two-body decays $B_c\to D^*h\to Dπh$ show an obvious hierarchy: $Br(B_{c}^+ \to D^{*+} K^{0}\to D^0π^+K^{0})=({5.22}_{-0.74}^{+0.86})\times{10}^{-6}, Br(B_{c}^+ \to D^{*+} π^{0}\to D^0π^+π^{0})=(0.93\pm0.26)\times{10}^{-7}, Br(B_{c}^+ \to D^{*+} η\to D^0π^+η) =({2.83}_{-0.52}^{+0.59})\times{10}^{-8}$ and $Br(B_{c}^+ \to D^{*+} η^\prime\to D^0π^+η^\prime)=({1.89}_{-0.36}^{+0.40})\times{10}^{-8}$. From the invariant mass $m_{Dπ}$-dependence of the decay spectrum for each channel, one can find that the branching fraction is concentrated in a narrow region around the $D^{*}$ pole mass. So one can obtain the branching ratios for the corresponding two-body decays $B_c\to D^{*+}h$ under the narrow width approximation. We find that the branching ratios of the decays $B_c\to D^{*+}h$ are consistent well with the previous PQCD calculations within errors. These predictions will be tested by the future experiments.

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arXiv2022

Insights into the nature of the $X(3872)$ through B meson decays

We study the decays $B_{c,u,d}\to X(3872)P$ in the perturbative QCD (PQCD) approach, where the puzzling resonance $X(3872)$ is involved and $P$ represents a light pseudoscalar meson $K$ and $π$. Assuming the $X(3872)$ as a $1^{++}$ charmonium state, we find the following results: (a) The branching ratios for the decays $B^+_c\to X(3872)π^+$ and $B^+_c\to X(3872) K^+$ agree with the results predicted by the covariant light-front approach within errors, but are larger than those given by the generalized factorization approach; (b) The branching ratio for the decay $B^+\to X(3872)K^+$ is predicted as $(3.8^{+1.1}_{-1.0})\times10^{-4}$, which is smaller than the previous PQCD calculation result, but still slightly larger than the upper limits set by Belle and BaBar. So we suggest that the decays $B^{0,+}\to X(3872)K^{0,+}$ should be precisely measured by the running LHCb and Belle II experiments, which is very helpful to probe the inner structure of the $X(3872)$; (c) Compared with the decays $B_{u,d}\to X(3872)K$, the decays $B_{u,d}\to X(3872)π$ have much smaller branching ratios, which drop to as low as $10^{-6}$; (d) The direct CP violations for these considered decays are very small, only $10^{-3}\sim 10^{-2}$, because the penguin contributions are loop suppressed compared with the tree contributions. Testing the results for the branching ratios and the CP violations including the implicit $SU(3)$ and isospin symmetries in these decays by experiments is helpful to probe the nature of the $X(3872)$.

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arXiv2022

Quasi-two-body decays $B_{(s)}\to K^*γ\to Kπγ$ in perturbative QCD approach

In this work we study the quasi-two-body decays $B\to K^*γ\to Kπγ$ in the perturbative QCD (PQCD) approach. The two-meson distribution amplitudes (DAs) are introduced to describe the final state interactions of the $Kπ$ pair, which involve the time-like form factors and the Gegenbauer polynomials. We calculate the CP averaged branching ratios for the decays $B_{(s)}\to K^*γ\to Kπγ$. Our results are in agreement with the new update data measured by Belle II, which suggests these quasi-two-body decays are more appropriate to be analyzed in three-body framework than in the two-body one. We also predict the direct CP-violation asymmetries for the considered decay modes and find that $A_{CP}(B_{u,d}\to K^*γ\to Kπγ)$ is small and less than $1\%$ in magnitude, while $A_{CP}(B_{s}\to K^*γ\to Kπγ)$ is larger and can arrive at a few percent. Our predictions can be tested by the future B meson experiments.

hep-ph↗