arXiv subjects

Mao-Zhi Yang

Publications and source records attributed to Mao-Zhi Yang.

At least 37 records · Page 2Linked to original sources

arXiv2017

Decay Constants and Distribution Amplitudes of B Meson in the Relativistic Potential Model

In this work we study the decay constants of $B$ and $B_s$ mesons based on the wave function obtained in the relativistic potential model. Our results are in good agreement with experimental data which enables us to apply this method to the investigation of $B$-meson distribution amplitudes. A very compact form of the distribution amplitude is obtained. We also investigate the one-loop QCD corrections to the pure leptonic decays of $B$ mesons. We find that, after subtracting the infrared divergence in the one-loop corrections using the factorization method, the QCD one-loop corrections to the hard amplitude of leptonic decay will be zero.

hep-ph↗

arXiv2016

Factorization of Radiative Leptonic Decays of $B^-$ and $D^-$ Mesons Including the Soft Photon Region

In this work, we study the radiative leptonic decays of $B^-$ and $D^-$ mesons using factorization approach. Factorization is proved to be valid explicitly at 1-loop level at any order of $O(Λ_{\rm QCD}\left/m_Q\right.)$. We consider the contribution in the soft photon region that $E_γ \sim \left. Λ^2_{\rm QCD} /\right. m_Q$. The numerical results shows that, the soft photon region is very important for both the $B$ and $D$ mesons. The branching ratios of $B\to γeν_e$ is $5.21\times 10^{-6}$, which is about $3$ times of the result obtained by only considering the hard photon region $E_γ\sim m_Q$. And for the case of $D\to γeν_e$, the result of the branching ratio is $1.92\times 10^{-5}$.

hep-ph↗

arXiv2016

Heavy-Light Mesons In A Relativistic Model

We study the heavy-light mesons in a relativistic model, which is derived from the instantaneous Bethe-Salpeter equation by applying the Foldy-Wouthuysen transformation on the heavy quark. The kernel we choose is based on scalar confining and vector Coulomb potentials, the transverse interaction of the gluon exchange is also taken into account in this model. The spectra and wave functions of $D$, $D_s$, $B$, $B_s$ meson states are obtained. The spectra are calculated up to the order of $1/m_Q$, and wave functions are treated to leading order.

hep-ph↗

arXiv2015

Effect of the Charged Higgs Bosons in the Radiative Leptonic Decays of $B^-$ and $D^-$ Mesons

In this work, we study the radiative leptonic decays of $B^-$ and $D^-$ mesons in the standard model and the two-Higgs-doublet-model type II. The results are obtained using the factorization procedure, and the contribution of the order $O(Λ_{\rm QCD}\left/m_Q\right.)$ is included. The numerical results are calculated using the wave-function obtained in relativistic potential model. As a result, the decay mode $B\to γτν_τ$ is found to be sensitive to the effect of the charged Higgs boson. Using the constraint on the free parameters of the two Higgs doublet model given in previous works, we find the contribution of the charged Higgs boson in the decay mode $B\to γτν_τ$ can be as large as about $13\%$.

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arXiv2015

Spectrum of Higher excitations of $B$ and $D$ mesons in the relativistic potential model

We study the masses and wave functions of heavy-light quark-antiquark system in the relativistic potential model, where we focus on the higher excited states of $B$ and $D$ mesons. The resonances of $D_J(2740)$, $D_J^*(2760)$, $D_J^*(3000)$ and $D_{sJ}^*(2860)$ recently observed in experiments are considered. We find that the four resonances can be identified as the $|1^{1,3}D_2\rangle$, $|1^3D_3\rangle$, $|1^{1,3}F_3\rangle$ and $|1^3D_3\rangle$ states due to the prediction to the states with $l=2$ and $l=3$ in the potential-model calculation. The masses of $n=2$ excited states are also calculated. All the observed mesons can be accommodated successfully in the potential model.

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arXiv2014

Factorization of Radiative Leptonic Decays of $B^-$ and $D^-$ Mesons

In this work, we study the factorization of the radiative leptonic decays of $B^-$ and $D^-$ mesons, the contributions of the order $O(Λ_{\rm QCD}\left/m_Q\right.)$ are taken into account. The factorization is proved to be valid explicitly at the order $O(α_sΛ_{\rm QCD}\left/m_Q\right.)$. The hard kernel is obtained. The numerical results are calculated using the wave-function obtained in relativistic potential model. The $O(Λ_{\rm QCD}\left/m_Q\right.)$ contribution is found to be very important, the correction to the decay amplitudes of $B^-\to γe\barν$ is about $20\% - 30\%$. For $D$ mesons, the $O(Λ_{\rm QCD}\left/m_Q\right.)$ contributions are more important.

hep-ph↗

arXiv2014

Spectrum of the charmed and b-flavored mesons in the relativistic potential model

We study the bound states of heavy-light quark-antiquark system in the relativistic potential model, where the potential includes the long-distance confinement term, the short-distance Coulomb term and spin-dependent term. The spectrum of $B$, $B^*$, $D$, $D^*$ and states with higher orbital quantum numbers are obtained. Compared with previous results predicted in the relativistic potential model, the predictions are improved and extended in this work, more theoretical masses are predicted which can be tested in experiment in the future.

hep-ph↗

arXiv2012

Study of the electromagnetic transitions $J/ψ\rightarrow P l^+l^-$ and probe dark photon

We study the electromagnetic Dalitz decay modes of $J/ψ\rightarrow P l^+l^-$ ($P= π^0$, $η$ or $η^\prime$). In these decays, the lepton pairs are formed by internal conversion of an intermediate virtual photon with invariant mass $m_{l^+l^-}$. Study of the effective-mass spectrum of the $l^+l^-$ will shed light on the dynamic transition form factor $F_{J/ψP}(q^2)$ ($q^2 = m^2_{l^+l^-}$), which characterizes the electromagnetic structure arising at the vertex of the transition $J/ψ$ to pseudoscalars. We also discuss the direct productions of a GeV scale vector $U$ boson in these processes $J/ψ\rightarrow PU$ ($U\rightarrow l^+l^-$). It is responsible for mediating a new $U(1)_d$ interaction, as recently exploited in the context of weakly interacting massive particle dark matter. In this paper, we firstly use the usual pole approximation for the form factor to estimate the decay rate of $J/ψ\rightarrow P l^+l^-$ in the standard model. Then the reach of searching for the dark photon is estimated. We suggest that these Dalitz decays can be used to search for the light $U$ boson in the BESIII experiment with a huge $J/ψ$ data set.

hep-ph↗

arXiv2012

Radiative Leptonic Decays of the charged $B$ and $D$ Mesons Including Long-Distance Contribution

In this work we study the radiative leptonic decays of $B^-$, $D^-$ and $D_s^-\to γl \barν$, including both the short-distance and long-distance contributions. The short-distance contribution is calculated by using the relativistic quark model, where the bound state wave function we used is that obtained in the relativistic potential model. The long-distance contribution is estimated by using vector meson dominance model.

hep-ph↗

arXiv2012

Wave functions and decay constants of $B$ and $D$ mesons in the relativistic potential model

With the decay constants of $D$ and $D_s$ mesons measured in experiment recently, we revisit the study of the bound states of quark and antiquark in $B$ and $D$ mesons in the relativistic potential model. The relativistic bound state wave equation is solved numerically. The masses, decay constants and wave functions of $B$ and $D$ mesons are obtained. Both the masses and decay constants obtained here can be consistent with the experimental data. The wave functions can be used in the study of $B$ and $D$ meson decays.

hep-ph↗

arXiv2011

Study on the mixing among the $0^{++}$ mesons around $1\sim 2$ $\mathrm{GeV}$ with the QCD sum rules

We calculate the correlation functions of $0^{++}$ $q\bar q$, $s\bar s$ and glueball in the QCD sum rules and obtain the mass matrix where non-diagonal terms are determined by the cross correlations among the three states. Diagonalizing the mass matrix and identifying the eigenstates as the physical $0^{++}$ scalar mesons, we can determine the mixing. Concretely, our calculations determine the fractions of $q\bar q$, $s\bar s$ and glueball in the physical states $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$, the results are consistent with that gained by the phenomenological research.

hep-ph↗

arXiv2010

Study of the branching ratio of $ψ(3770)\to D\bar{D}$ in $e^+e^-\to D\bar{D}$ scattering

Based on the data of BES and Belle, the production of $D\bar{D}$ in the $e^+e^-\to D\bar{D}$ scattering process is studied in this paper. We analyze the continuum and resonant contributions in the energy region from 3.7 to 4.4 GeV. In the $χ^2$ fit to data, we obtain the resonance parameters of $ψ(3770)$, the branching ratio of $ψ(3770)\to D\bar{D}$ decay by confronting the data to the theoretical formula where both the contributions of the resonances, continuum and interference effects are included. We obtain the branching ratio of $ψ(3770)\to D\bar{D}$ decay is $97.2%\pm 8.9%$, as well as the branching ratio of $ψ(4040)$, $ψ(4160)\to D\bar{D}$ decays.

hep-ph↗

arXiv2009

Radiative and leptonic decays of the pseudoscalar charmonium state $η_c$

The radiative and leptonic decays of $η_c\to γγ$ and $η_c\to l^+l^-$ are studied. For $η_c\to γγ$ decay, the second-order electromagnetic tree-level diagram gives the leading contribution. The decay rate of $η_c\to γγ$ is calculated, the prediction is in good agreement with the experimental data. For $η_c\to l^+ł^-$, both the tree and loop diagrams are calculated. The analysis shows that the loop contribution dominates, the contribution of tree diagram with $Z^0$ intermediate state can only modifies the decay rate by less than 1%. The prediction of the branching ratios of $η_c\to e^+e^-$ and $μ^+μ^-$ are very tiny within the standard model. The smallness of these predictions within the standard model makes the leptonic decays of $η_c$ sensitive to physics beyond the standard model. Measurement of the leptonic decay may give information of new physics.

hep-ph↗

arXiv2008

Rare Semileptonic Decays of Heavy Mesons with Flavor SU(3) Symmetry

In this paper, we calculate the decay rates of $D^+ \to D^0 e^+ ν$, $D^+_S \to D^0 e^+ ν$, $B^0_S \to B^+ e^- \barν$, $D^+_S \to D^+ e^- e^+$ and $B^0_S \to B^0 e^-e^+$ semileptonic decay processes, in which only the light quarks decay, while the heavy flavors remain unchanged. The branching ratios of these decay processes are calculated with the flavor SU(3) symmetry. The uncertainties are estimated by considering the SU(3) breaking effect. We find that the decay rates are very tiny in the framework of the Standard Model. We also estimate the sensitivities of the measurements of these rare decays at the future experiments, such as BES-III, super-$B$ and LHC-$b$.

hep-ph↗

arXiv2007

Strong Phase and $D^0-D^0bar$ mixing at BES-III

Most recently, both BaBar and Belle experiments found evidences of neutral $D$ mixing. In this paper, we discuss the constraints on the strong phase difference in $D^0 \to Kπ$ decay from the measurements of the mixing parameters, $y^\prime$, $y_{CP}$ and $x$ at the $B$ factories. The sensitivity of the measurement of the mixing parameter $y$ is estimated in BES-III experiment at $ψ(3770)$ peak. We also make an estimate on the measurements of the mixing rate $R_M$. Finally, the sensitivity of the strong phase difference at BES-III are obtained by using data near the $D\bar{D}$ threshold with CP tag technique at BES-III experiment.

hep-ex↗

arXiv2006

The continuum and interference effect in $e^+e^-\to D^0\bar{D}^0, D^+D^-$ processes

In the $e^+e^-$ annihilation processes $e^+e^-\to D^0\bar{D}^0, D^+D^-$ near or above the threshold of $D\bar{D}$, there are not only the resonance contribution $e^+e^-\to ψ(3770)\to D^0\bar{D}^0, D^+D^-$, but also the continuum contribution through virtual photon directly $e^+e^-\to γ^*\to D^0\bar{D}^0, D^+D^-$. The amplitudes through virtual photon directly and through resonance can interfere seriously. We consider the continuum and interference effect in the $D\bar{D}$ production process in $e^+e^-$ annihilation. We find that the effect is significant near and above the threshold of the $D\bar{D}$ mesons.

hep-ph↗

arXiv2006

D^0-D^0bar mixing in Υ(1S) \to D^0 D^0bar decay at Super-B

$\Dz-\Dzb$ mixing and significant CP violation in the charm system may indicate the signature of new physics. In this study, we suggest that the coherent $\DzDzb$ events from the decay of $Υ(1S) \to \Dz \Dzb$ can be used to measure both mixing parameters and CP violation in charm decays. The neutral $D$ mesons from $Υ(1S)$ decay are strongly boosted, so that it will offer the possibility to measure the proper-time interval, $Δt$, between the fully-reconstructed $\Dz$ and $\Dzb$. Both coherent and time-dependent information can be used to extract $\Dz-\Dzb$ mixing parameters. The sensitivity of the measurement should be improved at B factories or super-B.

hep-ph↗

arXiv2006

About Detecting CP-Violating Processes in $J/ψ\to \KzKzb $ Decay

Questions about detecting CP-violating decay process of $J/ψ\to K^0\bar{K}^0\to K_SK_S$ are discussed. Possible background and material regeneration effect are analyzed. The discussion can be directly extended to other vector quarkonium decays, like $Υ$, $ψ(2S)$ and $ϕ\to K_S K_S$.

hep-ex↗