The weak decays of $Λ_b \to Λl^{+} l^{-}$ ($l=e, μ$) are investigated in Minimal Supersymmetric Standard Model (MSSM) and also in Supersymmetric (SUSY) SO(10) Grand Unified Models. In MSSM the special attention is paid to the Neutral Higgs Bosons (NHBs) as they make quite a large contribution in exclusive $B \to X_{s} l^{+} l^{-}$ decays at large $\tanβ$ regions of parameter space of SUSY models, since part of SUSY contributions is proportional to $\tan^{3}β$. The analysis of decay rate, forward-backward asymmetries, lepton polarization asymmetries and the polarization asymmetries of $Λ$ baryon in $Λ_b \to Λl^{+} l^{-}$ show that the values of these physical observables are greatly modified by the effects of NHBs. In SUSY SO(10) GUT model, the new physics contribution comes from the operators which are induced by the NHBs penguins and also from the operators having chirality opposite to that of the corresponding SM operators. SUSY SO(10) effects show up only in the decay $Λ_b \to Λ+τ^{+} τ^{-}$ where the longitudinal and transverse lepton polarization asymmetries are deviate significantly from the SM value while the effects in the decay rate, forward-backward asymmetries and polarization asymmetries of final state $Λ$ baryon are very mild. The transverse lepton polarization asymmetry in $Λ_b \to Λ+τ^{+} τ^{-}$ is almost zero in SM and in MSSM model. However, it can reach to -0.1 in SUSY SO(10) GUT model and could be seen at the future colliders; hence this asymmetry observable will provide us useful information to probe new physics and discriminate between different models.
Exclusive Semileptonic Decays of B Mesons to Orbitally and Radial Excited D
本文在相对论夸克模型下计算了半轻子$\bar B \to X_c$衰变的Isgur-Wise函数,其中$X_c$是具有全自旋$J=0,1,2$或它们的第一激发态的粲介子.相关的矩阵元素计算的直接数值积分,在坐标空间中,的卷积的波函数的$B$介子在休息和$X_c$介子的波函数,根据其反冲因子提升。我们的研究结果与现有文献中发现的其他预测进行了比较。
Comment on $V_{ub}$ from Exclusive Semileptonic B and D Decays
讨论了由B排他半轻子衰变确定$|V_{ub}|$的前景。利用手征微扰理论计算了形状因子的二倍比$(f^{B\toρ}/f^{B\to K^*})/ (f^{D\toρ}/f^{D\to K^*})$。由于对称性破缺参数中的非解析贡献,它与单位的偏差非常小。结合可从(B->rho l nu)、(B->K* 11)和(D->rho l nu)获得的实验数据可导致$|V_{ub}|$的模型独立测定,其理论不确定度为约10%。
Constraints on Form Factors For Exclusive Semileptonic Heavy to Light Meson Decays
我们使用严格的QCD色散关系导出了B -> pi l nu,D -> pi l nu和D -> K l nu形状因子的模型无关的边界。当假设在一个或多个运动学点处的可观察形状因子的值时,这些界限特别具有限制性。在合理的假设下,我们发现f_B < 195 MeV,并且形状因子的形状受到严重限制。这些约束条件对于模型判别和CKM混合参数的模型不敏感提取都是有用的。
Supersymmetric effects in rare semileptonic decays of B and K mesons
罕见的味道改变中性电流转换类型的$s \to d \ell^+\ell^-(ν\barν)$和$b \to s \ell^+\ell^-(ν\barν)$分析超对称扩展的标准模型与通用味耦合。结果表明,这些过程是特别敏感的左-右混合的夸克,并在非通用的$A$条款的存在下,他们可能会导致明确的新物理的签名排他性$K$和$B$介子衰变。
In the wake of recent measurements of ratios of semileptonic branching fractions: ${\cal R}_{J/ψ}, {\cal R}_D$ and ${\cal R}_{D^*}$ reported by the LHCb, BELLE and HFLAV Collaborations, we calculate invariant form factors for the exclusive semileptonic $B_c$-meson decays to radially excited charmonium and charm meson states in the full kinematical region within the framework of relativistic independent quark (RIQ)model. We evaluate the lepton mass effect in the decay processes induced by $b\to c,u$ transition at the quark level. Our predictions on branching fractions for $B_c\to η_c/ψ(nS)$ are…
A phenomenological model for radiative corrections in exclusive semileptonic B-meson decays to (pseudo)scalar final state mesons
在$B$ -工厂实验中,次领先阶校正是提取Cabibbo-Kobayashi-Maskawa矩阵元素$|V_{\text{cb}}|$和$|V_{\text{ub}}|$的一个重要方面:虚光子和实光子耦合到衰变的所有带电粒子,改变产生的衰变动力学并提高总衰变率。提出了一个唯象模型和Monte-Carlo方法,研究了半轻子$B$介子衰变到赝标和标量末态的微分和总衰变率的电磁辐射修正,并将其分别应用于$B \to D \, l \, ν$和$B \to π\, l \, ν$以及$B \to D_0^* \, l \, ν$衰变.我们研究这样的修正与点状介子的现象学图片(与一些结构相关的修正),这是有效的,在低能量区域的光子,其结果,我们外推到完整的相空间。最大的可量化不确定性是由于与标准模型的近似匹配。此外,未知的结构依赖性贡献和模型依赖性可能会对我们的研究结果产生影响。
A nonrelativistic quark model evaluation of exclusive $b\to c$ semileptonic decay of triply heavy baryons and $c\to s,d$ semileptonic decay of $cb$ baryons
Exclusive semileptonic B decays to radially excited D mesons
在一级重夸克展开下研究了B衰变到径向激发粲介子的排斥性半轻子衰变。在相对论夸克模型的框架下计算了产生的主导和次主导Isgur-Wise函数。发现1/mQ修正起着重要的作用,并对结果有很大的修正。结果表明,不同修正量之间存在着一种有趣的相互作用,1/m_Q修正量使B-> D 'e ν衰变的分支比显著增加,而对B-> D' e ν衰变的分支比影响很小。
In this work, we discuss exclusive semileptonic $B_c$-meson decays: $B_c\to η_c(J/ψ)lν$ and $B_c\to D(D^*)lν$ in the framework of the relativistic independent quark(RIQ) model based on an average flavor independent confining potential in equally mixed scalar-vector harmonic form. We calculate the invariant form factors representing decay amplitudes from the overlapping integrals of meson wave functions derivable in the RIQ model. To evaluate the lepton mass effects in the semileptonic decays, we first study the $q^2$-dependence of the form factors in the accessible kinematic range of $q^2$ inv…