arXiv subjects

Mao-Zhi Yang

Publications and source records attributed to Mao-Zhi Yang.

At least 19 recordsLinked to original sources

arXiv2026

Phenomenological analysis of charmless $B\to PV$ decays in the modified perturbative QCD approach

We analyze the charmless two-body decays of the $B$ meson into a pseudoscalar and a vector meson, referred to as $B\to PV$ decay, within the framework of the modified perturbative QCD (PQCD) approach, which was originally developed to solve the long-standing puzzles, the so-called $ππ$ and $πK$ puzzles. In this method, based on the conventional PQCD calculations, soft form factors and contributions arising from color-octet quark-antiquark components in the final state are introduced, which involve essentially nonperturbative dynamics. By employing the flavor SU(3) symmetry and its breaking effect, the parameters describing soft contributions are correlated and subsequently reduced into a more concise set of SU(3) parameters. Through a $χ^2$ analysis procedure applied to the experimental data, these parameters are determined, from which the corresponding theoretical results for the branching ratios and $CP$ asymmetries in $B\to PV$ decays are derived. Within this framework, it is demonstrated that the theoretical calculations align well with experimental measurements, suggesting that the method developed for solving $ππ$ and $πK$ puzzles can be extended to more decay modes of the $B$ meson. The numerical analysis shows that these soft contributions have a significant influence on the theoretical results. Furthermore, more precise experimental data are needed for deeper investigations of the $CP$ asymmetries.

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arXiv2026

Branching ratios and CP violations of $B \toρ(ω) γ$ decays in the modified perturbative QCD approach and the relevant dark photonic decays of $B\to ρ(ω) γ^\prime $

In this work we study the radiative decays of $B\to ρ(ω)γ$ processes in the modified perturbative QCD approach, where the transverse momenta of the quark and gluons envolved in the interaction process are kept, and the Sudakov factor is incorporated in the theoretical calculation, which are helpful to suppress the infrared end-point contribution. A critical infrared momentum cutoff scale is introduced, which is used to separate the soft and hard contributions in QCD. Then the form factors envolved in the radiative decays should be separated as hard and soft form factors. The hard form factors can be calculated with the perturbative QCD approach, while the soft form factors should be viewed as soft input parameters. The soft form factors can be obtained by confronting the theoretical calculation of the branching ratios of the radiative decay of $B$ meson with the experimental data. Summing the soft and hard form factors, we find that the total form factors are in fine agreement with that obtained by nonperturbative theoretical method, such as the light-cone sum rules of QCD. We also study $B\to ρ(ω) γ^\prime$ decays by using the form factors obtained in the $B\to ρ(ω)γ$ decay processes, where $γ^\prime$ is the dark photon introduced by the extra $U(1)$ symmetry model. The upper limit of the branching ratios of thes decays are estimated.

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arXiv2025

Branching fraction, $CP$ asymmetry, and polarization in $B\toρρ$ decays with the modified perturbative QCD approach

In this work, we examine the observables associated with the $B\toρρ$ decays, including branching fractions, $CP$ asymmetry parameters, and longitudinal polarization fractions in the perturbative QCD (PQCD) approach with a few improvements. The essential distinction between this study and previous works lies in the introduction of an infrared cutoff at the critical scale $μ_c$, which is approximately at the scale of $1\;\text{GeV}$. The contributions above the critical scale are calculated using the PQCD approach, consistent with earlier studies, while the contributions below the scale $μ_c$ are regarded as nonperturbative and represented by some soft form factors. In addition, the distribution amplitude of the $B$ meson, derived from the relativistic potential model, and the contributions from the color-octet quark-antiquark components are also taken into account. With these modifications, we find that the theoretical results agree well with the experimental measurements for most observables, the introduction of the infrared cutoff enhances the reliability of the perturbation calculations, and the color-octet contributions play a key role in explaining the experimental data.

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arXiv2025

Study of $B\to πρ$, $πω$ decays in the modified perturbative QCD approach

We investigate the $B\toπρ$ and $πω$ decay processes using the modified perturbative QCD (PQCD) approach. Sudakov factors arising from the resummation of the double logarithms for the contributions of the transverse momenta of partons can increase the applicability of perturbative calculations. In this work we find that infrared contributions cannot be fully suppressed by Sudakov factors alone when the $B$ meson wave function obtained by solving the wave equation in the QCD-inspired relativistic potential model is used in the calculation of $B$ decays. Therefore, it is necessary to introduce a soft cutoff scale $μ_c$ to separate the hard and soft contributions. Color-octet contributions for the intermediate quark-antiquark pairs are considered. Such contributions are crucial to deminish the discrepancies between the theoretical calculation and experiemntal data. Using the isospin symmetry, we do find the optimal parameter space for the nonperturbative inputs, which can result in excellent agreement between the theoretical calculation and experimental data of $B\toπρ$ and $B\toπω$ decays.

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arXiv2025

Study of $B\rightarrow ρη$, $ρη^{\prime}$ decays in the modified perturbative QCD approach

We study the decay processes of $B\rightarrow ρη$, $ρη^{\prime}$ in the perturbative quantum chromodynamics (QCD) approach with a few improvements incorporated in it, where the contributions with large momentum transfer are calculated perturbatively, and the contributions with lower energy scale are treated by introducing soft transition form factors. In addition, color-octet contributions are introduced which are essentially long-distance contributions. With reasonable input parameters selected, we find that the theoretical results of the branching ratios and $CP$ violations are all consistent with experimental data. We also predict some unmeasured quantities, which can be tested by experiment in the future.

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arXiv2024

Revisiting $B\to K^*π$ and $B\to Kρ$ decays using the modified perturbative QCD approach

We revisit $B\to K^*π$ and $B\to Kρ$ decay processes using the modified perturbative QCD approach, which is developed based on the perturbative QCD approach with a few improvements. A critical infrared cutoff scale $μ_c$ is introduced to separate hard and soft contributions in the decay process. Hard contributions with scale $μ$ larger than $μ_c$ are calculated with perturbative QCD, and soft contributions with $μ<μ_c$ are described in terms of soft transition and production form factors. In addition, color-octet contributions are considered phenomenologically. The branching fractions and $CP$ violations of $B\to K^*π$, $Kρ$ decays are calculated. With appropriate parameter inputs, the theoretical results can be in good agreement with experimental data.

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arXiv2024

Study of $B\to PP$ decays in the modified perturbative QCD approach

We study the nonleptonic decays of $B\to PP$ in the modified perturbative QCD approach, where $P$ stands for pseudoscalar mesons. Transverse momenta of partons and the Sudakov factor are included, which help to suppress the contributions of soft interactions. The wave function of the $B$ meson obtained from the relativistic potential model is used, and then the contributions in the infrared region can not be suppressed completely. So a soft cutoff scale and soft form factors are introduced. The contributions with the scale higher than the soft cutoff scale are calculated with perturbative QCD, while the contributions lower than the cutoff scale are replaced by the soft form factors. To explain experimental data, we find that contributions of color-octet operators for the quark-antiquarks in the mesons in the final state need to be considered. The contributions of the color-octet operators are parametrized by a few parameters with the help of SU(3) flavor symmetry and symmetry breaking. These parameters for color-octet contributions are universal for all the nonleptonic decay modes of the $B$ meson, where the mesons in the final state belong to the same flavor SU(3) nonet. Both the branching ratios and $CP$ violations are studied. We find that the theoretical calculation can well explain the experimental data of $B$ factories.

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arXiv2023

Branching ratio and $CP$ violation of $B\to Kπ$ decays in a modified perturbative QCD approach

We calculate the branching ratio and $CP$ violations for $B\to Kπ$ decays in a modified perturbative QCD approach based on $k_{T}$ factorization. The resummation effect of the transverse momentum regulates the endpoint singularity. Using the $B$ meson wave function that is obtained in the relativistic potential model, soft contribution cannot be suppressed effectively by Sudakov factor. Soft scale cutoff and soft $BK$, $Bπ$ and $Kπ$ form factors have to be introduced. The most important next-to-leading-order contributions from the vertex corrections, the quark loops, and the magnetic penguins are also considered. In addition, the contribution of the color-octet hadronic matrix element is included which is essentially of long-distance dynamics. Our predictions for branching ratios and $CP$ violations are in good agreement with the experimental data. Especially the theoretical result of dramatic difference between the $CP$ violations of $B^+\to K^+π^0$ and $B^0\to K^+π^-$ is consistent with experimental measurement, therefore the $Kπ$ puzzle in $B$ decays can be resolved in our way of the modified perturbative QCD approach.

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arXiv2023

Possible solution of the puzzle for the branching ratio and $CP$ violation in $B\to ππ$ decays with a modified perturbative QCD approach

We study $B\to ππ$ decay with a modified perturbative QCD approach. The branching ratios and $CP$ violation are calculated with the transverse momenta of partons considered. Sudakov factor associated with each meson is included to suppress soft contribution in QCD. With the wave function of $B$ meson obtained in QCD-inspired relativistic potential model being used, the suppression of Sudakov factor to the soft contribution is not effective enough. Soft scale cutoff and soft form factors of $Bπ$ transition and $ππ$ production have to be introduced. The main next-to-leading-order contributions of vertex correction, the quark-loop and magnetic penguin are included. To solve the long-standing puzzle in $B\toππ$ decay, that is the theoretical prediction of the branching ratio of $B^0\to π^0π^0$ being seriously smaller than experimental data, color-octet matrix element which is of long-distance dynamics is introduced. With parameters taken with reasonable values, all the branching ratios and $CP$ violation are well consistent with experimental data.

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arXiv2021

Renormalization-Group Evolution of the None-local Matrix Element of $B$-meson In QCD and $B\to π$ transition form factor

We consider the renormalization-group evolution of the matrix element of $\langle 0| \bar{q}(z)_β[z,0]b(0)_α| \bar{B}\rangle$, which can be used to define the distribution amplitudes for $B$ meson and widely applied in studies of $B$ meson decays. The contribution to the renormalization constant of the non-local operator $\bar{q}(z)_β[z,0]b(0)_α$ is considered up to one-loop order in QCD. Since the quark fields in this operator are not directly coupled fields, momentum can not flow freely through this non-local operator. Momentum involved in this operator can be treated stringently in coordinate space. We find that the ultraviolet divergences regulated by dimensional parameter $ε$ cancel with each other, and the evolution effect vanishes. The matrix element $\langle 0| \bar{q}(z)_β[z,0]b(0)_α| \bar{B}\rangle$ escapes from the renormalization-group evolution. We then apply the matrix element in calculating $B\toπ$ transition form factor, where the matrix element is obtained by using the $B$ meson wave function calculated in QCD-inspired potential model. By comparing with experimental data for the semileptonic decay of $B\to π\ellν$ and light-cone sum rule calculation, we analyse the perturbative and non-perturbative contributions to $B\toπ$ transition form factor in the frame work of perturbative QCD approach. We find that the effectiveness of the suppression of Sudakov factor to soft contribution depends on the end-point behavior of $B$ meson wave function, and with the $B$-meson wave function used in this work, soft contribution can not be well suppressed. The hard contribution to the $B\toπ$ transition form factor is about 59\%, and soft contribution can be as large as 41\% in the naive calculation. To make the perturbative calculation reliable, a soft momentum cutoff in the calculation and soft form factor have to be introduced.

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arXiv2020

Study of semileptonic decay of $\bar{B}_s^0\to ϕl^+ l^-$ in QCD sum rule

In this work we study the semi-leptonic decay of $\bar{B}_s^0\to ϕl^+ l^-$($l=e, μ, τ$) with QCD sum rule method. We calculate the $\bar{B}_s^0\to ϕ$ translation form factors relevant to this semi-leptonic decay, then the branching ratios of $\bar{B}_s^0\to ϕl^+ l^-$($l=e, μ, τ$) decays are calculated with the form factors obtained here. Our result for the branching ratio of $\bar{B}_s^0\to ϕμ^+ μ^-$ agrees very well with the recent experimental data. For the unmeasured decay modes such as $\bar{B}_s^0\to ϕe^+ e^-$ and $\bar{B}_s^0\to ϕτ^+ τ^-$, we give theoretical predictions.

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arXiv2020

Form Factors and Decay of $\bar{B}_s^0\to J/ψϕ$ From QCD Sum Rule

We calculate $\bar{B}_s^0\to ϕ$ translation form factors $V$, $A_0$, $A_1$, $A_2$ based on QCD sum rule and study the nonleptonic two-body decay of $\bar{B}_s^0\to J/ψϕ$ with the form factors obtained. We calculate the time-integrated branching ratio of $\bar{B}_s^0\to J/ψϕ$ decay. The results for both the total branching ratio and the cases for the final vectors in longitudinal and transverse polarizations are consistent with experimental data.

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arXiv2020

Semileptonic Decay of $D_s^+\to π^0 \ell^+ ν_\ell$ Via Neutral Meson Mixing

Based on the mechanism of neutral meson mixing, we predict the branching fraction of the semileptonic decay of $D_s^+\to π^0 \ell^+ ν_\ell$ ($\ell=e$, $μ$) using recently measured branching fraction of $D_s^+\to ηe^+ν_e$ by BESIII experiment . We also give a formula that can describe the neutral meson mixing of $π^0$, $η$, $η'$ and a pseudoscalar gluonium $G$ in a unified way. The predicted branching fraction of $D_s^+\toπ^0 e^+ν_e$ decay is $\mathcal{B}(D_s^+\toπ^0 e^+ν_e)=(2.65\pm 0.38)\times 10^{-5}$. It is important to search for the decay $D_s^+\to π^0 \ell^+ ν_\ell$ in experiment, in order to understand the mechanism of $π^0$ production in $D_s^+\toπ^0$ transition in semileptonic decay. We also estimate the branching fraction of $D_s^+\to π^0τ^+ν_τ$, which is the only kinematically allowed semi-tauonic decay mode of the charmed meson, since the mass value of $D_s^+$ meson is just slightly above the threshold of $π^0τ^+$ generation in the semi-tauonic decay.

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arXiv2019

Study of the electromagnetic Dalitz decays $ψ(Υ) \to η_{c}(η_{b}) l^{+} l^{-}$

We study the electromagnetic Dalitz (EM) decays, $ψ\to η_{c} l^{+} l^{-}$ and $Υ\to η_{b} l^{+} l^{-}$ ($l = e$ or $μ$), in which the lepton pair comes from the virtual photon emitted by the M1 transition from $c\bar{c}$ ($b\bar{b}$) spin triplet state to the spin singlet state. We estimate the partial width of $ψ(Υ) \to η_{c}(η_{b}) l^{+} l^{-}$, based on the simple pole approximation. Besides, based on different QCD models, the partial width of $ψ(Υ) \to η_{c}(η_{b}) γ$ is determined.

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arXiv2019

Testing SU(3) Flavor Symmetry in Semileptonic and Two-body Nonleptonic Decays of Hyperons

The semileptonic decays and two-body nonleptonic decays of light baryon octet ($T_8$) and decuplet ($T_{10}$) consisting of light $u,d,s$ quarks are studied with the SU(3) flavor symmetry in this work. We obtain the amplitude relations between different decay modes by the SU(3) irreducible representation approach, and then predict relevant branching ratios by present experimental data within $1 σ$ error. We find that the predictions for all branching ratios except $\mathcal{B}(Ξ\rightarrow Λ^0π)$ and $\mathcal{B}(Ξ^*\rightarrow Ξπ)$ are in good agreement with present experimental data, that implies the neglected $C_+$ terms or SU(3) breaking effects might contribute at the order of a few percent in $Ξ\rightarrow Λ^0π$ and $Ξ^*\rightarrow Ξπ$ weak decays. We predict that $\mathcal{B}(Ξ^{-}\rightarrow Σ^0μ^-\barν_μ)=(1.13\pm0.08)\times10^{-6}$, $\mathcal{B}(Ξ^{-}\rightarrowΛ^0μ^-\barν_μ)=(1.58\pm0.04)\times10^{-4}$, $\mathcal{B}(Ω^-\rightarrowΞ^0μ^-\barν_μ)=(3.7\pm1.8)\times10^{-3}$, $\mathcal{B}(Σ^-\rightarrow Σ^0e^-\barν_e)=(1.35\pm0.28)\times10^{-10}$, $\mathcal{B}(Ξ^-\rightarrow Ξ^0e^-\barν_e)=(4.2\pm2.4)\times10^{-10}$. We also study $T_{10}\to T_8 P_8$ weak, electromagnetic or strong decays. Some of these decay modes could be observed by the BESIII, LHCb and other experiments in the near future. Due to the very small life times of $Σ^0$, $Ξ^{*0,-}$, $Σ^{*0,-}$ and $Δ^{0,-}$, the branching ratios of these baryon weak decays are only at the order of $\mathcal{O}(10^{-20}-10^{-13}$), which are too small to be reached by current experiments. Furthermore, the longitudinal branching ratios of $T_{8A} \to T_{8B} \ell^- \barν_\ell~(\ell=μ,e)$ decays are also given.

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arXiv2019

Wave Functions and Leptonic Decays of Bottom Mesons In the Relativistic Potential Model

We study the wave functions and purely leptonic decays of $b$-flavored mesons (pseudoscalars, vector mesons, and higher excited states that are well established in experiment) in the relativistic potential model based on our previous works. The wave functions are obtained by solving the wave equation including the spin-spin and spin-orbit corrections in the effective potential. The decay constants of $B$, $B^*$ and some of their excited states that have been found in experiment are calculated with these wave functions. Then the branching fractions of the purely leptonic decay modes of these bottom mesons are studied. Our results are in well agreement with experiment data for decay modes that have been measured in experiments. We also provide predictions for some yet unmeasured channels, which are useful for experimental test in the future.

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arXiv2018

Study of the isospin breaking decay $\mathbf{\boldsymbol{Y(2175)\rightarrowϕf_0(980)\rightarrowϕηπ^0}}$ at BESIII

Using measured branching fraction of the decay $J/ψ\rightarrowηY(2175))\rightarrowηϕf_0(980)\rightarrowηϕπ^+π^{-}$ from the BESIII experiment, we estimate branching fraction of $J/ψ\rightarrowηY(2175))\rightarrowηϕf_0(980)\rightarrowηϕηπ^{0}$ decay, which proceeds via the $f_0(980)$-$a_0^0(980)$ mixing and the $π^0$-$η$ mixing. The branching fraction is predicted to be about $O(10^{-6})$, which can be accessed with $10^{10}$ $J/ψ$ events collected at the BESIII. The decay is dominated by the contribution from $f_0(980)$-$a_0^0(980)$ mixing. We find that the interference between the amplitudes due to $f_0(980)$-$a_0^0(980)$ mixing and that due to $π^0$-$η$ mixing is destructive. The branching fraction can be decreased by about $10\%$ owing to the interference effect. We also study the $ηπ^0$ mass squared spectrum, and find that a narrow peak due to the $f_0(980)$-$a_0^0(980)$ mixing in the $ηπ^0$ mass squared spectrum should be observed. The observation of this decay in experiment will be helpful to determine the $f_0(980)$-$a_0^0(980)$ mixing intensity and get information about the structures of the light scalar mesons.

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arXiv2017

Study of $\mathbf{\boldsymbol{D \rightarrow a_0 (980) e^+ ν_e}}$ decay in the light-cone sum rules approach

Within the QCD light-cone sum rule (LCSR) approach, we investigate the transition form factors of $D\rightarrow a_0(980)$ up to the twist-3 light-cone distribution amplitudes (LCDAs) of the scalar meson $a_0(980)$ in the two-quark picture. Using these form factors, we calculate the differential decay widths and branching ratios of the $D\rightarrow a_0(980) e^+ ν_e$ semileptonic decays. We obtain ${\mathcal B}(D^0\rightarrow a_0^- (980) e^+ ν_e)=(4.08^{+1.37}_{-1.22})\times 10^{-4}$ and ${\mathcal B}(D^+\rightarrow a_0^0 (980) e^+ ν_e)=(5.40^{+1.78}_{-1.59})\times 10^{-4}$. The results are sensitive to the $a_0(980)$ inner structure. These decays can be searched for at BESIII experiment, and any experimental observations will be useful to identify internal quark contents of the $a_0(980)$ meson, which will shed light on understanding theoretical models.

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