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Tsung-Wen Yeh

Publications and source records attributed to Tsung-Wen Yeh.

16 recordsLinked to original sources
arXiv2018

Minimal QCDF Model for $B\toπK$ Puzzle

In this work, we propose a model by combining the parameterization method and the QCD factorization to study the $B\toπK$ puzzle. The parameterization introduces twelve parameters, the weak angle $γ$ and the other eleven hadronic parameters. These hadronic parameters are calculated by the QCD factorization (QCDF). The calculational accuracy of the QCDF is improved by including the twist-3 three parton tree and one loop corrections. Three additional nonperturbative strong phases from the gluonic penguin, color suppressed, and color favored tree diagrams are required to account for the direct CP asymmetries. The weak angle, three nonperturbative strong phases, and four scale variables are assumed as fitting parameters. These eight parameters are determined by a least squares fit to the eight measurements. The fit shows that the hadronic parameters need to be process-dependent. The process-dependent hadronic parameters break the isospin symmetry `dynamically'. A large negative relative phase associated with the internal up quark gluonic penguin diagram is observed. The weak angle $γ$ is found to be $72.1\pm5.8$ degree, being consistent with the world averaged value, $72.1\pm5.8$ degree. By a least squares fit to the mixing induced asymmetry $S(π^{0}K_{S})=0.58\pm0.06$, the weak angle $β$ is determined to be $22.9\pm2.1$ degree, which is in a well agreement with the world averaged value, $22.5\pm4.4\pm0.6$ degree. The model predicts the ratio $C^{\prime}/T^{\prime}$ (color suppressed/color favored) to be $0.59\pm0.08$. The above evidences indicate that the model can solve the $B\toπK$ puzzle consistently.

hep-ph↗
arXiv2008

$B$ to $π$ Form Factors in collinear factorization approach

The form factors for semi-leptonic B decays, $\bar{B}\toπl\barν_l$, are calculated under collinear factorization approach. The end-point divergences are regularized by a $ξ$-regularization, where $ξ$ means the collinear fraction of the spectator anti-quark of the $\bar{B}$ meson. The form factors are calculated up-to $O(α_{s}/m_{B})$. The complete $O(1/m_{B})$ contributions from the $π$ meson are calculated explicitly by a collinear expansion method. A well-defined power expansion scheme is built such that the $O(1/m_{B})$ contributions are about 30% of the leading order contributions. A small value $F_+(0)=0.164$ is found. This confirms the SCET result $F_+(0)=0.17$ from $B\toππ$ decays. The form factors are calculated for {\normalsize $0\leq q^{2}\leq16 \text{GeV}^{2}$}, where $q^2$ is the invariant mass of the lepton pair in $\bar{B}\toπl\barν_l$. An extrapolation of the form factors to $q^{2}>16 \text{GeV}^{2}$ is made to obtain {\normalsize $|V_{ub}|^{-2}\int_{0}^{26.42 \text{GeV}^{2}}dq^{2}(dΓ/dq^{2})_{\text{th}}=(5.71\pm 0.91)ps^{-1}$}. We determine $|V_{ub}|=(3.95\pm 0.13_{\text{exp}}\pm 0.32_{\text{th}})\times 10^{-3}$ from the world averaged branching ratio $Br(\bar{B}\toπl\barν_{l})=(1.36\pm 0.09)\times 10^{-4}$.

hep-ph↗
arXiv2008

QCD factorization at twist-3: the two parton contributions

In this paper, the twist-3 two parton corrections in charmless $B\to PP$ decays are shown to be factorizable under the QCD factorization approach. The factorizability of the twist-3 two parton corrections is constructed on the following findings. Under the energetic meson limit, the pseudoscalar distribution amplitude for a light pseudoscalar meson is allowed to be non-constant by the equations of motion for the quark. The non-constant pseudoscalar distribution amplitude is then used to regularize the end-point divergences in the hard spectator corrections at twist-3 order. By retaining the momentum fraction variable of the spectator quark of the $B$ meson in the propagators, the end-point divergence in the weak annihilation corrections at twist-3 order is resolved. The factorization of the $O(α_s)$ corrections under the two parton approximation is shown valid up-to $O(1/m_b)$ . The hard scattering kernels of order $O(α_s)$ and $O(Λ_{QCD}/m_b)$ are explicitly given and found to be infrared finite. The results are applied for making predictions for the branching ratios of $B\to πK $ decays.

hep-ph↗
arXiv2008

Three Parton Corrections in $B\to PP$ decays

The $1/m_b$ corrections from the three parton $q\bar{q}g$ Fock state of the final state light meson in $B\to PP$ decays are evaluated by means of a collinear expansion method. The impacts of these corrections on the $CP$ averaged branching ratios of the $B\to πK$ decays are analyzed.

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arXiv2002

$η-η^\prime$ mixing and the next-to-leading-order power correction

The next-to-leading-order $O(1/Q^4)$ power correction for $ηγ$ and $η^\primeγ$ form factors are evaluated and employed to explore the $η-η^\prime$ mixing. The parameters of the two mixing angle scheme are extracted from the data for form factors, two photon decay widths and radiative $J/ψ$ decays. The $χ^2$ analysis gives the result: $f_{η_1}=(1.16\pm0.06)f_π, f_{η_8}=(1.33\pm0.23)f_π, θ_1=-9^\circ\pm 3^\circ, θ_8=-21.3^\circ\pm 2.3^\circ$, where $f_{η_{1(8)}}$ and $θ_{1(8)}$ are the decay constants and the mixing angles for the singlet (octet) state. In addition, we arrive at a stringent range for $f_{η^\prime}^c:-10$ MeV$\le f_{η^\prime}^c\le -4$ MeV.

hep-ph↗
arXiv2002

Polarization and Distribution Function of $Λ_b$ Baryon

The polarization of $Λ_b$ baryon has been measured in ALEPH, OPAL and DELPHI experiments. A significant loss on the transfer of the $b$ quark polarization to the $Λ_b$ baryon polarization has been noticed. This implies that the hadronization effects can not be neglected. Therefore, we may make use of the polarization measurements to look for suitable model for the $Λ_b$ distribution function. To investigate nonperturbative effects implied in the $Λ_b$ polarization, we construct four models based on a perturbative QCD factorization formula. The models are the quark model (QM), the modified quark model (MQM), the parton model (PM), and the modified parton model (MPM). The modified models mean the models having transverse degrees of freedom and the associated soft radiative corrections having been resummed. The quark and parton models can not describe all experiments in the same time. On the other hand, the modified models can have the power to explain all data in the same formalism.

hep-ph↗
arXiv2001

A New Formulation for HQET

We proposed a new formulation for heavy quark effective theory (HQET), whose Lagrangian is hermitian and has a manifest reparameterization invariance. As an application, we calculated the semileptonic and nonleptonic inclusive heavy hadron decay rates up to second order mass corrections and found that there are no kinetic energy correction terms.

hep-ph↗
arXiv1998

PQCD Analysis of Inclusive Semileptonic Decays of A Polarized Lambda_b Baryon

We investigate the Lambda_b polarization problem in the inclusive semileptonic decays of a polarized Lambda_b baryon, using the modified perturbative QCD formalism which includes Sudakov suppression. According to HQEFT, we show that, at the leading order in the 1/M_b expansion, the polarized and unpolarized distribution functions become one single universal distribution function. To explore the mechanisms which determine the spin properties of a polarized Lambda_b baryon, we construct four formalisms which are the naive quark model (QM), the modified quark model (MQM), the naive parton model (PM) and the modified parton model (MPM), and calculate their corresponding Lambda_b polarizations, denoted as P's. The modified quark and parton models are with Sudakov suppression. The resulting P's are -0.23 (QM), -0.94 (MQM), -0.37 (PM) and -0.68 (MPM), respectively. We note that P_MQM (equal to -0.94) is very close the b quark polarization asymmetry, A_RL=-0.94, calculated at the Z vertex in Z -> b bar{b} process, and that P_MPM (equal to -0.68) is also very close to the Lambda_b polarization (equal to -0.68) which was estimated from the fragmentation processes under the heavy quark limit. Based on our analysis, there exists no any paradox in the theoretical explanations of the Lambda_b polarization for the experimental data.

hep-ph↗
arXiv1997

Factorization theorems, effective field theory, and nonleptonic heavy meson decays

The nonleptonic heavy meson decays $B\to D^{(*)}π(ρ), J/ψK^{(*)}$ and $D\to K^{(*)}π$ are studied based on the three-scale perturbative QCD factorization theorem developed recently. In this formalism the Bauer-Stech-Wirbel parameters a_1 and a_2 are treated as the Wilson coefficients, whose evolution from the W boson mass down to the characteristic scale of the decay processes is determined by effective field theory. The evolution from the characteristic scale to a lower hadronic scale is formulated by the Sudakov resummation. The scale-setting ambiguity, which exists in the conventional approach to nonleptonic heavy meson decays, is moderated. Nonfactorizable and nonspectator contributions are taken into account as part of the hard decay subamplitudes. Our formalism is applicable to both bottom and charm decays, and predictions, including those for the ratios R and R_L associated with the $B\to J/ψK^{(*)}$ decays, are consistent with experimental data.

hep-ph↗
arXiv1996

Internal W-emmission and W-exchange Contributions to {\bf B}\to {{\bf D}^{(*)} Decays

We evaluate external $W$-emission, internal $W$-emission and $W$-exchange contributions to nonleptonic $B\to D^{(*)}$ decays based on the perturbative QCD formalism including Sudakov effects, whose ratio is found to be $1:+0.2:0.03i$ at the amplitude level. We observe that the internal $W$-emission contribution is additive to the external $W$-emission contribution, and that the $W$-exchange contribution is negligible and mainly imaginary, its real part being at least one order of magnitude smaller than the imaginary part. Our predictions are consistent with the CLEO data and with those obtained by the Bauer-Stech-Wirbel method.

hep-ph↗
arXiv1995

Perturbative QCD study of $B\to D^{(*)}$ decays

We compute various form factors involved in $B\to D^{(*)}$ transitions based on the perturbative QCD formalism, which includes Sudakov effects from the resummation of large radiative corrections in a heavy-light system. A two-parameter model wave function for $D^{(*)}$ mesons is fixed using data of the nonleptonic decays $B\to D^{(*)}π$, from which the ratio of the decay constants $f_{D^*}/f_D=0.92$ is obtained. We then derive the spectrum of the semileptonic decay $B\to D^{*}\ellν$ in the fast recoil region of the $D^*$ meson, and extract the CKM matrix element $|V_{cb}|=0.043\times(0.12 {\rm GeV}/f_B)\times(0.14 {\rm GeV}/f_D)$, $f_B$ and $f_D$ being the $B$ and $D$ meson decay constants, respectively. Here we adopt the convention with the pion decay constant $f_π=93$ MeV. With these outcomes, we evaluate the decay rate of $B\to DD_s$, and estimate the ratio $f_{D_s}/f_D=0.98$ from data. Contributions of internal $W$-emission and $W$-exchange diagrams are briefly discussed.

hep-ph↗
arXiv1995

On the mass correction of heavy meson effective theory

We derive the mass correction lagrangian of the heavy meson effective theory by using the projection operator method. The next leading order of the mass correction and the first order of the chiral expansion are given explicitely.We also consider the mass correction weak lagrangian of the heavy mesons. Finally, we give the $\it{D}^{*+}\to \it{D}^o π^{+}$ decay.

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