arXiv subjects

Sheng Lü

Publications and source records attributed to Sheng Lü.

5 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.

hep-ph↗

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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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

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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