arXiv subjects

Wen-Fei Wang

Publications and source records attributed to Wen-Fei Wang.

At least 37 records · Page 2Linked to original sources

arXiv2019

Quasi-two-body decays $B \to D K^*(892) \to D K π$ in the perturbative QCD approach

We study the quasi-two-body decays $B\to D K^*(892) \to D Kπ$ by employing the perturbative QCD approach. The two-meson distribution amplitudes $Φ_{Kπ}^{\text{$P$-wave}}$ are adopted to describe the final state interactions of the kaon-pion pair in the resonance region. The resonance line shape for the $P$-wave $Kπ$ component $K^*(892)$ in the time-like form factor $F_{Kπ}(s)$ is parameterized by the relativistic Breit-Wigner function. For most considered decay modes, the theoretical predictions for their branching ratios are consistent with currently available experimental measurements within errors. We also disscuss some ratios of the branching fractions of the concerned decay processes. More precise data from LHCb and Belle-II are expected to test our predictions.

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arXiv2019

Virtual contributions from $D^{\ast}(2007)^0$ and $D^{\ast}(2010)^{\pm}$ in the $B\to Dπh$ decays

We study the quasi-two-body decays $B\to D^*h \to Dπh$ with $h=(π, K)$ in the perturbative QCD approach and focus on the virtual contributions from the off-shell $D^{\ast}(2007)^0$ and $D^{\ast}(2010)^{\pm}$ in the four measured decays $\bar B^0 \to D^0π^+π^-$, $\bar B^0\to D^0π^+K^-$, $B^- \to D^+π^-π^-$ and $B^- \to D^+π^-K^-$. For the $\bar B^0 \to D^{*+}π^-\to D^0π^+π^-$ and $\bar B^0\to D^{*+}K^-\to D^0π^+K^-$ decays, their branching fractions concentrate in a very small region of $m_{D^0π^+}$ near $D^{*+}$ pole mass, and the virtual contributions from $D^{*+}$, in the region $m_{D^0π^+}>2.1$ GeV, are about $5\%$ of the corresponding quasi-two-body results. We define two ratios $R_{D^{*+}}$ and $R_{D^{*0}}$, from which we conclude that the flavor-$SU(3)$ symmetry will be maintained for the $B\to D^* h\to Dπh$ decays with very small breaking at any physical value of the $m_{Dπ}$. The $B^-\to D^{*0}π^-\to D^0π^0π^-$ and $B^-\to D^{*0}K^-\to D^0π^0K^-$ decays can be employed as a constraint for the $D^{*0}$ decay width, with preferred values consistent with previous theoretical predictions for this quantity.

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arXiv2019

Quasi-two-body decays $B_{(s)}\to K^*(892)h\to Kπh$ in perturbative QCD approach

We extend our recent works on the $P$-wave two-pion resonant contributions to the kaon-pion cases in the hadronic charmless $B$ meson decays by employing the perturbative QCD approach. The concerned decay modes are analysed in the quasi-two-body framework by parameterizing the kaon-pion distribution amplitude $Φ_{K π}^{\rm P}$, which contains the final state interactions between the kaon and pion in the resonant region. The relativistic Breit-Wigner formula for the $P$-wave resonant state $K^*(892)$ is adopted to parameterize the time-like form factor $F_{Kπ}$. We calculate the $CP$-averaged branching ratios and direct $CP$-violating asymmetries of the quasi-two-body decays $B_{(s)}\to K^*(892) h\to Kπh$, with $h=(π, K)$, in this work. It is shown that the agreement of theoretical results with the experimental data can be achieved, through which Gegenbauer moments of the $P$-wave kaon-pion distribution amplitudes are determined. The predictions in this work will be tested by the precise data from the LHCb and the future Belle II experiments.

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arXiv2018

Resonant state $D_0^\ast(2400)$ in the quasi-two-body $B$ meson decays

We study four quasi-two-body decay processes including $D^\ast_0(2400)$ as the intermediate state in perturbative QCD (PQCD) approach. The branching fraction predicted in this work for the decay mode $B^-\to D^{*}_0(2400)^0π^-\to D^+π^-π^-$ agree with the data from Belle, BaBar and LHCb Collaborations. The PQCD prediction of the branching ratio for the decay $\bar B^0\to D^{*+}_0K^-\to D^0π^+K^-$ is consistent with the value given by LHCb. For the decays $\bar B^0\to D^{*+}_0π^-\to D^0π^+π^-$ and $B^-\to D^{*0}_0K^-\to D^+π^-K^-$, the PQCD predicted branch ratios are $2.85^{+1.23}_{-0.80}(ω_B)^{+1.05}_{-0.81}(ω_{Dπ})^{+0.33}_{-0.31}(a_{Dπ})^{+0.06}_{-0.05}(Γ_{D^{*+}_0}) \times 10^{-4}$ and $4.65^{+1.89}_{-1.30}(ω_B)^{+1.51}_{-1.24}(ω_{Dπ})^{+0.40}_{-0.38}(a_{Dπ})^{+0.22}_{-0.18}(Γ_{D^{*0}_0}) \times 10^{-5}$, respectively. We analyze the experimental branching fractions using the ratios $R_{D^{*0}_0}$ and $R_{D^{*+}_0}$ which are related to the decays with the neutral and charged $D^\ast_0(2400)$, respectively. The available experimental results for the quasi-two-body decays including $D^\ast_0(2400)$ are not in agreement with the isospin relation and $SU(3)$ flavor symmetry.

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arXiv2018

Quasi-two-body decays $B_{(s)}\to P f_2(1270)\to Pππ$ in the perturbative QCD approach

In this work, we calculate the $CP$-averaged branching ratios and direct $CP$-violating asymmetries of the quasi-two-body decays $B_{(s)}\to P f_2(1270)\to Pππ$ with the two-pion distribution amplitude $Φ_{ππ}^{\rm D}$ by using the perturbative QCD factorization approach, where $P$ represents a light pseudoscalar meson $K, π, η$ and $η^{\prime}$. The relativistic Breit-Wigner formula for the $D$-wave resonance $f_2(1270)$ is adopted to parameterize the timelike form factor $F_π$, which contains the final state interactions between the pions in the resonant regions. The consistency of theoretical results with data can be achieved by determining the Gegenbauer moments of the $D$-wave two-pion distribution amplitudes. The decay rates for the considered decay modes are generally in the order of $10^{-9}$ to $ 10^{-6}$. The integrated direct $CP$ asymmetries for the charged modes agree with the {\it BABAR} and Belle measurements. As a by-product, we extract the branching ratios of $B_{(s)}\to Pf_2(1270)$ from the corresponding quasi-two-body decay modes, which still need experimental tests at the ongoing and forthcoming experiments.

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arXiv2018

$S$-wave $Kπ$ contributions to the hadronic charmonium $B$ decays in the perturbative QCD approach

We extend our recent works on the two-pion $S$-wave resonance contributions to the kaon-pion ones in the $B$ meson hadronic charmonium decay modes based on the perturbative QCD approach. The $S$-wave $Kπ$ time-like form factor in its distribution amplitudes is described by the LASS parametrization, which consists of the $K^*_0(1430)$ resonant state together with an effective range nonresonant component. The predictions for the decays $B\rightarrow J/ψKπ$ in this work agree well with the experimental results from $BABAR$ and Belle Collaborations. We also discuss theoretical uncertainties, indicating the results of this work, which can be tested by the LHCb and Belle-II experiments, are reasonably accurate.

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arXiv2017

Quasi-two-body decays $B_{(s)} \to D (ρ(1450),ρ(1700)) \to D ππ$ in the perturbative QCD factorization approach

By employing a framework for the quasi-two-body decays in the perturbative QCD (PQCD) factorization approach, we calculate the branching ratios of the decays $B_{(s)} \to D (ρ(1450),ρ(1700))\to D ππ$ with $D=(D_{(s)}, \bar{D}_{(s)})$. The pion vector form factor $F_π$, acquired from a {\it BABAR} Collaboration analysis of $e^+ e^- \to π^+ π^-(γ)$ data, is involved in the two-pion distribution amplitudes $Φ^{I=1}_{ππ}$. The PQCD predictions for the branching ratios of the considered quasi-two-body decays are in the range of $10^{-10} \sim 10^{-4}$. The PQCD predictions for ${\cal B}(B^0\to \bar{D}^0 (ρ^0(1450),ρ^0(1700)) \to \bar{D}^0 π^+π^-)$ agree well with the measured values as reported by LHCb if one takes still large theoretical errors into account. Unlike the traditional way of the PQCD approach, one can extract the decay rates for the two-body decays $B_{(s)} \to D (ρ(1450),ρ(1700))$ from the results of the corresponding quasi-two-body decays. The PQCD predictions for ${\cal B}(B_{(s)} \to D ρ(1450))$ and ${\cal B}(B_{(s)} \to D ρ(770))$ are similar in magnitude: an interesting relation to be tested by future experimental measurements.

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arXiv2017

The quasi-two-body decays $B_{(s)} \to (D_{(s)},\bar{D}_{(s)}) ρ\to (D_{(s)}, \bar{D}_{(s)})ππ$ in the perturbative QCD factorization approach

In this paper, we studied the $B_{(s)} \to (D_{(s)},\bar{D}_{(s)}) ρ\to (D_{(s)}, \bar{D}_{(s)})ππ$ decays by employing a framework for the quasi-two-body decays in the perturbative QCD (PQCD) factorization approach. We use the two-pion distribution amplitudes $Φ_{ππ}$, which contains both resonant and nonresonant contributions from the pion pair, to describe the final state interactions (FSIs) between the pions in the resonant region. We found that (a) for all considered decays, the PQCD predictions for their branching ratios based on the quasi-two-body and the two-body framework agree well with each other due to ${\cal B}(ρ\to ππ) \approx 100\%$; For $B^+\to \bar{D^0}ρ^+\to \bar{D^0}π^+ π^0$ and other four considered decay modes, the PQCD predictions do agree well with the measured values within errors; (b) the great difference between the PQCD predictions for ${\cal B}(B\to \bar{D} ρ\to \bar{D} ππ)$ and ${\cal B}(B\to D ρ\to D ππ)$ can be understood by the strong CKM suppression factor $ R_{\rm CKM} \approx 3 \times 10^{-4}$; (c) for the $B_s\to D ρ\to D ππ$ and $B_s\to \bar{D} ρ\to \bar{D} ππ$ decays, however, the PQCD predictions of $R_{\rm s1}\approx 0.13$ and $R_{\rm s2}\approx 0.14$ do agree very well with the moderate CKM suppression factor $R^s_{\rm CKM}\approx 0.14$; and (d) the PQCD predictions for the ratios $R_{Dρ}$ and the strong phase difference $\cosδ_{Dρ}$ of the three $B \to \bar{D} ρ$ decay modes agree well with the LHCb measurements within one standard deviation.

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arXiv2017

Quasi-two-body decays $B_{(s)}\to Pρ^\prime(1450), Pρ^{\prime\prime}(1700)\to Pππ$ in the perturbative QCD approach

In this work, we calculate the $CP$-averaged branching ratios and direct $CP$-violating asymmetries of the quasi-two-body decays $B_{(s)}\to P ρ^\prime(1450), Pρ^{\prime\prime}(1700)\to P ππ$ by employing the perturbative QCD (PQCD) factorization approach, where $P$ is a light pseudoscalar meson $K, π, η$ and $η^{\prime}$. The considered decay modes are studied in the quasi-two-body framework by parameterizing the two-pion distribution amplitude $Φ_{ππ}^{\rm P}$. The $P$-wave time-like form factor $F_π$ in the resonant regions associated with the $ρ^\prime(1450)$ and $ρ^{\prime\prime}(1700)$ is estimated based on available experimental data. The PQCD predictions for the $CP$-averaged branching ratios of the decays $B_{(s)}\to Pρ^\prime(1450), Pρ^{\prime\prime}(1700)\to Pππ$ are in the order of $10^{-7} \sim 10^{-9}$. The branching ratios of the two-body decays $B_{(s)}\to Pρ^\prime(1450), Pρ^{\prime\prime}(1700)$ are extracted from the corresponding quasi-two-body decay modes. The whole pattern of the pion form factor-squared $|F_π|^2$ measured by {\it BABAR} Collaboration could also be understood based on our studies. Our PQCD predictions will be tested by the precise data from the LHCb and the future Belle II experiments.

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arXiv2017

$S$-wave resonance contributions to the $B^0_{(s)}\to η_c{(2S)}π^+π^-$ in the perturbative QCD factorization approach

By employing the perturbative QCD (PQCD) factorization approach, we study the quasi-two-body $B^0_{(s)}\to η_c{(2S)}π^+π^-$ decays, where the pion pair comes from the $S$-wave resonance $f_0(X)$. The Breit$-$Wigner formula for the $f_0(500)$ and $f_0(1500)$ resonances, and the Flatté model for the $f_0(980)$ resonance are adopted to parameterize the time-like scalar form factors in the two-pion distribution amplitudes. As a comparison, Bugg's model is also used for the wide $f_0(500)$ in this work. For decay rates, we found the following PQCD predictions: (a) $ {\cal B}(B^0_s\to η_c(2S) f_0(X)[π^+π^-]_s )=\left ( 2.67^{+1.78}_{-1.08} \right )\times 10^{-5}$ when the contributions from $f_0(980)$ and $f_0(1500)$ are all taken into account; (b) ${\cal B}(B^0\to η_c(2S) f_0(500)[π^+π^-]_s)= \left ( 1.40 ^{+0.92}_{-0.56} \right ) \times 10^{-6}$ in the Breit-Wigner model and $ \left ( 1.53 ^{+0.97}_{-0.61} \right ) \times 10^{-6}$ in the Bugg's model.

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arXiv2017

The S-wave resonance contributions in the $B^0_s$ decays into $ ψ(2S,3S)$ plus pion pair

The three-body decays $B^0_s \rightarrow ψ(2S,3S) π^+ π^-$ are studied based on the perturbative QCD approach. With the help of the nonperturbative two-pion distribution amplitudes, the analysis is simplified into the quasi-two-body processes. Besides the traditional factorizable and nonfactorizable diagrams at the leading order, the next-to-leading order vertex corrections are also included to cancel the scale dependence. The $f_0(980)$, $f_0(1500)$ resonance contributions as well as the nonresonant contributions are taken into account using the presently known $ππ$ time-like scalar form factor for the $s\bar{s}$ component. It is found that the predicted $B^0_s \rightarrow ψ(2S) π^+ π^-$ decay spectra in the pion pair invariant mass shows a similar behavior as the experiment. The calculated S-wave contributions to the branching ratio of $B^0_s \rightarrow ψ(2S) π^+ π^-$ is $6.0\times 10^{-5}$, which is in agreement with the LHCb data $\mathcal {B}(B^0_s \rightarrow ψ(2S) π^+ π^-)=(7.2\pm 1.2)\times 10^{-5} $ within errors. The estimate of $\mathcal {B}(B^0_s \rightarrow ψ(3S) π^+ π^-)$ can reach the order of $10^{-5}$, pending for the corresponding measurements.

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arXiv2017

Quasi-two-body decays $B_{(s)}\to Pρ\to Pππ$ in perturbative QCD approach

In this work, we calculate the $CP$-averaged branching ratios and the direct $CP$-violating asymmetries of the quasi-two-body decays $B_{(s)} \to P (ρ\to) ππ$ by employing the perturbative QCD (PQCD) approach (here $P$ stands for a light pseudoscalar meson $π, K, η$ or $η^{\prime}$). The vector current time-like form factor $F_π$, which contains the final state interactions between the pion pair in the resonant region associated with the $P$-wave states $ρ(770)$ along with the two-pion distribution amplitudes, are employed to describe the interactions between the $ρ$ and the pion pair under the hypothesis of the conserved vector current. We found that (a) the PQCD predictions for the branching ratios and the direct $CP$-violating asymmetries for most considered $B_{(s)} \to P (ρ\to) ππ$ decays agree with currently available data within errors; (b) for ${\cal B}(B \to π^0 ρ^0 \to π^0(π^+ π^-)$, the PQCD prediction is much smaller than the measured one; and (c) for $B^+ \to π^+(ρ^0\to)π^+ π^-$ decay mode, we found a negative $CP$ asymmetry $(-27.5^{+3.0}_{-3.7})\%$, which agrees with other theoretical predictions but different in sign from those as reported by BaBar and LHCb Collaboration.

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arXiv2016

The $S$-wave resonance contributions to the three-body decays $B^0_{(s)}\to η_c f_0(X)\to η_cπ^+π^-$ in perturbative QCD approach

In this paper, we study the three-body decays $B^0/B^0_s \to η_c f_0(X)\to η_c π^+π^-$ by employing the perturbative QCD (PQCD) factorization approach. We evaluate the $S$-wave resonance contributions by using the two-pion distribution amplitude $Φ_{ππ}^{\rm S}$. The Breit-Wigner formula for the $f_0(500)$, $f_0(1500)$, and $f_0(1790)$ resonances and the Flatté model for the $f_0(980)$ resonance are adopted to parameterize the time-like scalar form factors $F_{s}(ω^2)$. We also use the D.~V.~Bugg model to parameterize the $f_0(500)$ and compare the relevant theoretical predictions from different models. We found the following results: (a) the PQCD predictions for the branching ratios are ${\cal B}(B^0\to η_c f_0(500)[π^+π^-])= \left ( 1.53 ^{+0.76}_{-0.35} \right ) \times 10^{-6}$ for Breit-Wigner model and ${\cal B}(B^0\to η_c f_0(500)[π^+π^-])= \left ( 2.31 ^{+0.96}_{-0.48} \right ) \times 10^{-6}$ for D.~V.~Bugg model; (b) $ {\cal B}(B_s\to η_c f_0(X)[π^+π^-] ) =\left ( 5.02^{+1.49}_{-1.08} \right )\times 10^{-5}$ when the contributions from $f_0(X)=(f_0(980),f_0(1500),f_0(1790))$ are all taken into account; and (c) The considered decays could be measured at the ongoing LHCb experiment, consequently, the formalism of two-hadron distribution amplitudes could also be tested by such experiments.

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arXiv2016

Quasi-two-body decays $B\to Kρ\to Kππ$ in perturbative QCD approach

We analyze the quasi-two-body decays $B\to Kρ\to Kππ$ in the perturbative QCD (PQCD) approach, in which final-state interactions between the pions in the resonant regions associated with the $P$-wave states $ρ(770)$ and $ρ^\prime(1450)$ are factorized into two-pion distribution amplitudes. Adopting experimental inputs for the time-like pion form factors involved in two-pion distribution amplitudes, we calculate branching ratios and direct $CP$ asymmetries of the $B\to Kρ(770),Kρ^\prime(1450)\to Kππ$ modes. It is shown that agreement of theoretical results with data can be achieved, through which Gegenbauer moments of the $P$-wave two-pion distribution amplitudes are determined. The consistency between the three-body and two-body analyses of the $B\to Kρ(770)\to Kππ$ decays supports the PQCD factorization framework for exclusive hadronic $B$ meson decays.

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arXiv2015

The $B_c\rightarrow ψ(2S)π$, $η_c(2S)π$ decays in the perturbative QCD approach

Nonleptonic two body $B_c$ decays including radially excited $ψ(2S)$ or $η_c(2S)$ mesons in the final state are studied using the perturbative QCD approach based on $k_T$ factorization. The charmonium distribution amplitudes are extracted from the $n = 2, l = 0$ Schr$\ddot{o}$dinger states for the harmonic oscillator potential. Utilizing these distribution amplitudes, we calculate the numerical results of the $B_c\rightarrow ψ(2S),η_c(2S)$ transition form factors and branching fractions of $B_c\rightarrow ψ(2S)π, η_c(2S)π$ decays. The ratio between two decay modes $B_c\rightarrow ψ(2S)π$ and $B_c\rightarrow J/ψπ$ is compatible with the experimental data within uncertainties, which indicate that the harmonic oscillator wave functions for $ψ(2S)$ and $η_c(2S)$ work well. It is found that the branching fraction of $B_c\rightarrow η_c(2S)π$, which is dominated by the twist-3 charmonium distribution amplitude, can reach the order of $10^{-3}$. We hope it can be measured soon in the LHCb experiment.

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arXiv2015

$S$-wave resonance contributions to the $B^0_{(s)}\to J/ψπ^+π^-$ and $B_s\toπ^+π^-μ^+μ^-$ decays

We study $S$-wave resonance contributions to the $B^0_{(s)}\to J/ψπ^+π^-$ and $B_s\toπ^+π^-\ell^+\ell^-$ decays in the perturbative QCD (PQCD) framework by introducing two-hadron distribution amplitudes for final states. The Breit-Wigner formula for the $f_0(500)$, $f_0(1500)$ and $f_0(1790)$ resonances and the Flatté model for the $f_0(980)$ resonance are adopted to parameterize the time-like scalar form factors in the two-pion distribution amplitudes, which include both resonant and nonresonant contributions. The resultant branching fraction and differential branching fraction in the pion-pair invariant mass for each resonance channel are consistent with experimental data. The determined $S$-wave two-pion distribution amplitudes, containing the information of both resonant and nonresonant rescattering phases, can be employed to predict direct CP asymmetries of other three-body hadronic $B$ meson decays in various localized regions of two-pion phase space.

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arXiv2014

Semileptonic decays $B_c^+\to D^{(*)}_{(s)}(l^+ν,l^+l^-,ν\barν)$ in the perturbative QCD approach

In this paper we study the semileptonic decays of $B_c^+\to D^{(*)}_{(s)}(l^+ν_l,l^+l^-,ν\barν)$ (here $l$ stands for $e$, $μ$, or $τ$). After evaluating the $B_c^+ \to (D_{(s)},D^*_{(s)})$ transition form factors $F_{0,+,T}(q^2)$ and $V(q^2), A_{0,1,2}(q^2), T_{1,2,3}(q^2)$ by employing the perturbative QCD factorization approach, we calculate the branching ratios for all these semileptonic decays. Our predictions for the values of the $B_c^+ \to D_{(s)}$ and $B_c^+ \to D^*_{(s)}$ transition form factors are consistent with those obtained by using other methods. The branching ratios of the decay modes with $\barνν$ are almost an order of magnitude larger than the corresponding decays with $l^+l^-$ after the summation over the three neutrino generations. The branching ratios for the decays with $b\to d$ transitions are much smaller than those decays with the $b\to s$ transitions, due to the Cabibbo-Kobayashi-Maskawa suppression. We define ratios $R_D$ and $R_{D^*}$ for the branching ratios with the $τ$ lepton versus $μ$, $e$ lepton final states to cancel the uncertainties of the form factors, which could possibly be tested in the near future.

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arXiv2014

The semileptonic decays of $B/B_s$ meson in the perturbative QCD approach: A short review

In this short review, we present the current status about the theoretical and experimental studies for some important semileptonic decays of $B/B_s$ mesons. We firstly gave a brief introduction for the experimental measurements for $B/B_s \to P (l^+l^-, l^-\barν_l, ν\barν)$ decays, the BaBar's $R(D)$ and $R(D^*)$ anomaly, the $P_5^\prime$ deviation for $B^0 \to K^{*0} μ^+ μ^-$ decay. We then made a careful discussion about the evaluations for the relevant form factors in the light-cone QCD sum rule (LCSRs), the heavy quark effective theory, and the perturbative QCD factorization approach. By using the form factors calculated in the perturbative (pQCD) approach, we then calculate and show the pQCD predictions for the decay rates of many semileptonic decays of $B/B_s$ mesons. We also made careful phenomenological analysis for these pQCD predictions and found, in general, the following points: (a) For all the considered $B/B_s$ semileptonic decays, the next-to-leading order (NLO) pQCD predictions for their decay rates agree well with the data and those from other different theoretical methods; (b) For $R(D)$ and $R(D^*)$, the pQCD predictions agree very well with the data, the BaBar's anomaly of $R(D^{(*)})$ are therefore explained successfully in the standard model by employing the pQCD approach; and (c) We defined several new ratios $R_D^{l,τ}$ and $R_{D_s}^{l,τ}$, they may be more sensitive to the QCD dynamics which controls the $B/B_s \to (D^{(*)},D_s^{(*)})$ transitions than the old ratios, we therefore strongly suggest LHCb and the forthcoming Super-B experiments to measure these new ratios.

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