Within the framework of HQET, $Λ_{b}\rightarrowΛ_{c}τ\barν_τ$ and $Ω_{b}\rightarrowΩ_{c}^{(*)}τ\barν_τ$ weak decays are studied to the order of $1/m_c$ and $1/m_b$. Helicity amplitudes are written down. Relevant Isgur-Wise functions given by QCD sum rule and large $N_c$ methods are applied in the numerical analysis. The baryonic R-ratios $R(Λ_c)$ and $R(Ω_c^{(*)})$ are obtained.
Charged Higgs Effects on Exclusive Semi-tauonic $\bbox{B}$ Decays
研究了$B$半轻子衰变$\bar B \rightarrow D^{(*)}τ\barν_τ$中带电希格斯玻色子交换效应。研究了分支比和$τ$极化。为了减少强子形状因子的理论不确定性,我们利用了最近的半轻子$B$衰变的实验数据和重夸克有效理论。分支比的理论不确定性被发现是相当小的,在$τ$极化几乎可以忽略不计。他们的测量将对带电的希格斯扇区给出非平凡的约束。
There is growing evidence for deviation from the standard model predictions in the ratios between semi-tauonic and semi-leptonic $B$ decays, known as the $R(D^{(*)})$ puzzle. If the source of this non-universality is new physics, it is natural to assume that it also breaks CP symmetry. In this paper we study the possibility of measuring CP violation in semi-tauonic $B$ decays, exploiting interference between excited charm mesons. Given the current values of $R(D^{(*)})$, we find that our proposed CP-violation observable could be as large as about 10%. We discuss the experimental advantages of …
Lepton flavor universality can be tested in the semileptonic decays $Λ_b\to Λ_c^{(\ast)}$ where $Λ_c^{(\ast)}$ denotes either the ground state $Λ_c(2286)$ (with $J^P=1/2^+$) or its orbital excitations $Λ_c(2595)$ (with $J^P=1/2^-$) and $Λ_c(2625)$ (with $J^P=3/2^-$). We calculate the differential decay rates as well as the branching fractions of these decays for both tauonic and muonic modes with form factors obtained from a covariant confined quark model previously developed by us. We present results for the rate ratios of the tauonic and muonic modes which provide important tests of lepton f…
QCD corrections to charged Higgs-mediated $b \to c τν$ decay
我们计算了荷电Higgs介导的包容性半τ介子$B$衰变的$O(α_s)$修正。在朗道规范下,我们演示了如何从已知的QCD对$t \to b H^+$的修正中获得带电的Higgs贡献(包括直接项和干涉项)。结合我们的结果与$O(1/m_b^2)$修正的旁观者模型和比较的理论预测与最近的实验测量,我们发现一个模型无关的$2σ$上界的希格斯真空期望值的比率,$\tanβ<0.52(m_H/1 GeV)$。
We propose improved Lepton Flavor Universality (LFU) ratios in semileptonic $P\to V \ell \barν$ decays, when comparing $μ$ and $τ$ modes, that minimize the theoretical form-factor uncertainties. These optimized ratios are obtained with simple cuts or reweighting of the dilepton mass distributions, which imply a minimum loss of signal on the rare tauonic modes while maximizing the cancellation of theoretical uncertainties among the two modes. We illustrate the usefulness of these observables in $B_c\to J/ψ$, $B_c\to ψ(2S)$, $B\to D^\ast$ and $B_s\to D_s^\ast$ transitions, showing that in all ca…
Radiative corrections to the three-body region of the Dalitz plot of baryon semileptonic decays with angular correlation between polarized emitted baryons and charged leptons: The initial-baryon rest frame case
The semileptonic transition of $Λ_b$ baryon is studied using the Hypercentral constituent quark model. The six-dimensional hyperradial $Schr\ddot{o}dinger$ equation is solved in the variational approach to get masses and wavefunctions of heavy baryons. The matrix elements of weak decay are written in terms of the overlap integrals of the baryon wave function. The Isgur-Wise function is determined to calculate exclusive semileptonic decay $Λ_b$ $\rightarrow$ $Λ_c$ $\ell$ $\barν$. The calculated decay rate and the branching ratio of $Λ_b$ baryon are consistent with other theoretical predictions …
Radiative corrections to the three-body region of the Dalitz plot of baryon semileptonic decays with angular correlation between polarized emitted baryons and charged leptons
The static properties and semileptonic decays of ground-state doubly heavy baryons are studied working in the framework of a non-relativistic quark model. Using a phenomenological potential model, we calculate the ground-state masses and magnetic moments of doubly heavy $ Ω$ and $ Ξ$ baryons. In the heavy quark limit, we introduce a simple form of the universal Isgur-Wise function used as the transition form factor and then investigate the exclusive $ b \rightarrow c $ semileptonic decay widths and branching ratios for $ \frac{1}{2}\rightarrow \frac{1}{2} $ baryon transitions. Our obtained res…
Semileptonic decays of heavy baryons in the relativistic quark model
在重夸克-轻双夸克近似下,研究了由一个重夸克(Q=b,c)和两个轻夸克(q=u,d,s)组成的重子的半轻子衰变.在组分夸克模型中,利用相对论准势方程计算了双夸克和重子的质量和波函数。弱跃迁矩阵元由重子波函数的重叠积分表示。Isgur-Wise函数在整个可达运动学范围内确定。利用重夸克1/mQ展开计算了唯一的半轻子衰变率和不同的不对称性。评估的Lambda_b -> Lambda_c l nu衰变率与其实验值一致。
In the framework of a non-relativistic quark model, the mass spectra of the ground and excited states of doubly heavy $Ξ$ and $Ω$ baryons are calculated. We estimate the mass difference between the $ Ω$ and corresponding $ Ξ$ baryons as $M_Ω-M_Ξ\simeq178 $ MeV for all the states containing $ cc,~bc $, or $ bb $ quarks. A simple form of the universal Isgur-Wise function, as the transition form factor between the doubly heavy baryons, is introduced. Working in the close-to-zero recoil limit, we investigate the $ b \rightarrow c $ semileptonic decay widths and branching fractions of the doubly he…
Relativistic description of semileptonic decays of heavy baryons
在重夸克-轻双夸克近似下,研究了由一个重夸克(Q=b,c)和两个轻夸克(q=u,d,s)组成的重子的半轻子衰变.在组分夸克模型中,用相对论准势方程计算了双夸克和重子的质量和波函数。弱跃迁矩阵元由重子波函数的重叠积分表示。Isgur-Wise函数是在整个可达运动学范围内确定的。用重夸克1/mQ展开计算了唯一的半轻子衰变率。评估的Lambda_b -> Lambda_c l nu衰变率与其实验值一致。
Precision radiative corrections to the semileptonic Dalitz plot with angular correlation between polarized decaying and emitted baryons: Effects of the four-body region
Precision radiative corrections to the semileptonic Dalitz plot with angular correlation between polarized decaying baryon and emitted charged lepton: Effects of the four-body region
The semileptonic decays of $Λ_{b}\toΛ_{c}^{(*)}\ellν_\ell$ and $Λ_{c}\toΛ^{(*)}\ellν_\ell$ are studied in the light-front quark model in this work. Instead of the quark-diquark approximation, we use the three-body wave functions obtained by baryon spectroscopy. The ground states $(1/2^{+})$, the $λ$-mode orbital excited states $(1/2^{-})$, and the first radial excited states $(1/2^{+})$ of $Λ_{(c)}^{(*)}$ are considered. The discussions are given for the form factors, partial widths, branching fractions, leptonic forward-backward asymmetries, hadron polarizations, lepton polarizations, and the…
Hyperfine mixing in $b\to c$ semileptonic decay of doubly heavy baryons
我们定性地证实了W. Roberts和M. Pervin in Int. J. Mod. Phys. A 24,2401(2009),根据该文献,超精细混合极大地影响了涉及双重重$bc$重子的$b\to c$半轻子衰变的衰变宽度。然而,我们对未混合态的衰变宽度的预测与Roberts和Pervin的工作中报道的结果相差2倍,这种差异转化为混合态。我们进一步表明,重夸克自旋对称性的预测,可能会被用于在未来的实验中提取信息的实际物理$bc$重子的混合物,在一个模型独立的方式。
Numerical precision radiative corrections to the Dalitz plot of light and heavy quark unpolarized baryon semileptonic decays. The cases Xi^0 \to Sigma^+ e \barν and Λ_c^+ \to Λe^+ ν
我们提出并讨论了我们以前的精确结果的数值使用非极化自旋二分之一重子半轻子衰变的辐射校正,这是不妥协的固定形状因子在规定的值。我们提出了各种crosscheriches和其他结果的比较,在文献中的这种分析辐射校正。然而,我们的分析是通用的,适用于重夸克允许的重子的所有电荷分配。该过程以过程^+ e \bar v和Λ_c^+ \to Λe^+ v为例。
Precision radiative corrections to the Dalitz plot of baryon semileptonic decays including the spin-momentum correlation of the decaying baryon and the emitted charged lepton
Form factors of the weak $Ξ_c \to Ξ(Λ)$ transitions are calculated within the light cone QCD sum rules. The pollutions coming from the contribution of the negative parity $Ξ_c^*$ baryon is eliminated by considering the combinations of sum rules corresponding to the different Lorentz structures. Having obtained the form factors, the branching ratios of the $Ξ_c \to Ξ(Λ) \ell ν$ decays are also calculated, and our predictions are compared with the results of other approaches as well as the measurements done by BELLE and ALICE Collaborations.