Decay constants of pseudoscalar and vector mesons with improved holographic wavefunction

We calculate the decay constants of light and heavy-light pseudoscalar and vector mesons with improved soft-wall holographic wavefuntions,which take into account the effects of both quark masses and dynamical spins.We find that the predicted decay constants,especially for the ratio f V/f P,based on light-front holographic QCD,can be significantly improved,once the dynamical spin effects are taken into account by introducing the helicity-dependent wavefunctions.We also perform detailed χ~2 analyses for the holographic parameters(i.e.the mass-scale parameterκ and the quark masses),by confronting our predictions with the data for the charged-meson decay constants and the meson spectra.The fitted values for these parameters are generally in agreement with those obtained by fitting to the Regge trajectories.At the same time,most of our results for the decay constants and their ratios agree with the data as well as the predictions based on lattice QCD and QCD sum rule approaches,with only a few exceptions observed.     

Effects of a Family Non-universal Z' Boson in B_d → μ~+μ~-and B~-→ π~-μ~+μ~-,ρ~-μ~+μ~-Decays

Motivated by the recently updated experimental measurement on Bˉd →μ+μ and B →πμ+μ decays by CDF and Belle collaborations,we revisit these decays,as well as B →ρμ+μ decay,within the Standard Model,and evaluate the effects of a family non-universal Z' boson.Under the constraint from B(B →πμ+μ),we find the ranges of the Z' couplings SμLμR 5.2 × 10 2 or DμLμR 8.1 × 10 2 are excluded.Within the allowed Z' parameters spaces,comparing with the SM predictions,we find that B(Bˉd →μ+μ),B(B →πμ+μ),and B(B →ρμ+μ) could be enhanced by a factor about 226%,245%,and 254%,respectively,by Z' contributions.However,they are hardly to be reduced.Furthermore,the zero crossing in the normalized forward-backward asymmetry spectrum of B →ρμ+μ decay at low dimuon mass always exists.     

基于Python的科里奥利力对物体运动影响的可视化模拟

为了直观清晰地观察地球自转产生的科里奥利力效应，本文以抛体和傅科摆运动为例，基于Python编程的计算机模拟和可视化图像分析方法，详细探究了不同运动条件下科里奥利力对物体运动影响的异同及其原因，描绘出转动参考系中“相对运动—横向偏移—科里奥利力”之间关系的物理图像。通过计算模拟将抽象的理论可视化，有效地促进学生对物理过程的深刻理解，培养学生计算思维和创新思维能力，提高学生分析和解决问题的能力。     

Fourth generation effects in ■_s→π~-K+ decay

We study the effects of the fourth quark generation model in ■_s →π-K+decay.Combining with the up-to-date experimental measurement for B(■_s →π-K +) and A dir cp(■_s →π-K +) by the CDF Collaboration,we derive the new bound of weak phase φ bd,which are 0 < φ bd < 44,321 < φ bd < 360 and 0 < φ bd < 26,342 < φ bd < 360 for m t = 400 and 600 GeV respectively.In these regions,B(■_s →π-K +) and A dir cp(■_s →π-K +) consist with the current experimental data within errors.     

Fourth generation effects in Bs→π^-K^＋ decay

We study the effects of the fourth quark generation model in B_s → π^-K⁺ decay. Combining with the up-to-date experimental measurement for B(B_s → π^-K⁺) and A_cp^dir(B_s → π^-K⁺) by the CDF Collaboration, we derive the new bound of weak phase ø_bd, which are 0°< ø_bd <44°, 321°< ø_bd < 360° and 0°< ø_bd < 26°, 342°< ø_bd < 360° for m_t'=400 and 600 GeV respectively. In these regions, B(B_s → π^-K⁺) and A_cp^dir(B_s → π^-K⁺) consist with the current experimental data within errors.     

Acoustic radiation force on a rigid cylinder near rigid corner boundaries exerted by a Gaussian beam field

Acoustic manipulation is one of the well-known technologies of particle control and a top research in acoustic field. Calculation of acoustic radiation force on a particle nearby boundaries is one of the critical tasks, as it approximates realistic applications. Nevertheless, it is quite difficult to solve the problem by theoretical method when the boundary conditions are intricate. In this study, we present a finite element method numerical model for the acoustic radiation force exerting on a rigid cylindrical particle immersed in fluid near a rigid corner. The effects of the boundaries on acoustic radiation force of a rigid cylinder are analyzed with particular emphasis on the non-dimensional frequency and the distance from the center of cylinder to each boundary. The results reveal that these parameters play important roles in acoustic manipulation for particle-nearby complicated rigid boundaries. This study verifies the feasibility of numerical analysis on the issue of acoustic radiation force calculation close to complex boundaries, which may provide a new idea on analyzing the acoustic particle manipulation in confined space.     

自由空间中球形粒子的负向声辐射力

针对一定声场作用下自由空间中的球形粒子,首先分析了声散射过程中的吸收声功率、散射声功率和损失声功率以及三者之间的关系,并通过计算发现了由于参数选取不当导致的负吸收现象。接着从动量守恒定律出发推导了声辐射力的一般表达式,阐释了声辐射力与声能流之间的关系,并从理论和计算两方面验证了负向声辐射力的存在。当负向声辐射力产生时,声波的背向散射被抑制。在此基础上,进一步研究了粒子的偏心特性和流体的黏度这两种常见因素对负向声辐射力的影响。利用球函数的加法公式推导了偏心球的散射系数和声辐射力公式,结果显示偏心距离、粒子的材料等都会显著改变负向声辐射力的产生条件。在低频近似下,由于流体黏度附加的正向声辐射力是否能完全抵消原来的负向声辐射力将决定最终的声辐射力方向。该结果对利用负向声辐射力制成单行波声学镊子来实现对特定粒子的操控有着理论指导意义。      

声悬浮高温小球轴向稳定性研究

针对驻波声悬浮高温小球的轴向稳定性,建立了声-热-流-重力场耦合的物理模型,采用有限元方法计算了高温小球周围空间的不均匀温度场和声场,分析了驻波声场中直径2 mm的氮化硅小球在300～2000 K温度区间的轴向悬浮稳定性,并通过常温下声悬浮实验验证了仿真模型的准确性。结果表明在初始悬浮间距满足谐振并保持不变的条件下,随着悬浮小球的温度升高,小球的平衡位置降低,并且存在能保持稳定悬浮状态的温度最大值。在小球升温的过程中,通过反馈调节发射端-反射端间距和发射端激励电压,可以在一定程度上保持高温小球的轴向悬浮稳定性。