We present in this work a study of tree-dominated charmless three-body decays of $B$ mesons, $B^-\to K^+K^-π^-$ and $B^-\toπ^+π^-π^-$, within the factorization approach. The main results are: (i) There are two distinct sources of nonresonant contributions: one arises from the $b\to u$ tree transition and the other from the nonresonant matrix element of scalar densities $\langle M_1M_2|\bar q_1 q_2|0\rangle^{\rm NR}$. It turns out that even for tree-dominated three-body decays, dominant nonresonant contributions originate from the penguin diagram rather than from the $b\to u$ tree process, as implied by the large nonresonant component observed recently in the $π^- K^+$ system which accounts for one third of the $B^-\to K^+K^-π^-$ rate. (ii) The calculated branching fraction of $B^-\to f_2(1270)π^-\to K^+K^-π^-$ is smaller than the LHCb by a factor of $\sim 7$ in its central value, but the predicted $\B(B^-\to f_2(1270)π^-\toπ^+π^-π^-)$ is consistent with the data. Branching fractions of $B^-\to f_2(1270)π^-$ extracted from the LHCb measurements of these two processes also differ by a factor of seven! Therefore, it is likely that the $f_2(1270)$ contribution to $B^-\to K^+K^-π^-$ is largely overestimated experimentally. Including $1/m_b$ power corrections from penguin annihilation inferred from QCD factorization (QCDF), a sizable CP asymmetry of 32\% in the $f_2(1270)$ component agrees with experiment. (iii) A fraction of 5\% for the $ρ(1450)$ component in $B^-\toπ^+π^-π^-$ is in accordance with the theoretical expectation. However, a large fraction of 30\% in $B^-\to K^+K^-π^-$ is entirely unexpected. This issue needs to be clarified in the future.
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 o…
Summary of CKM 2023 working group 5: Direct CP violation (DCPV) including $ϕ_{3}/γ$ from $B\to DK$, DCPV effects, branching fractions and polarisation in charmless $B_{(s)}$ decays
本文总结了CKM2023研讨会工作组5的活动，涵盖了利用$B\ o DK$测量$ϕ_{3}/γ$、在无粲$B$及$b$重子衰变中寻找$CP$破坏、强子$B$到粲衰变分支比测量以及三体非轻子$B$衰变理论的新结果。
We report the status of the Heavy Flavour Averaging Group (HFLAV) averages of the $τ$ lepton measurements We then update the latest published HFLAV global fit of the $τ$ lepton branching fractions (Spring 2017) with recent results by BABAR. We use the fit results to update the Cabibbo-Kobayashi-Maskawa (CKM) matrix element Vus measurements with the $τ$ branching fractions. We combine the direct $τ$ branching fraction measurements with indirect predictions using kaon branching fractions measurements to improve the determination of Vus using $τ$ branching fractions. The Vus determinations based …
Production of the matter-antimatter asymmetry in the $B$-Mesogenesis mechanism is directly related to the branching fraction of seemingly baryon number violating decays of $B$ mesons into a light Standard Model baryon and missing energy. Achieving the observed baryon asymmetry requires that the branching fraction for such decays be greater than about $10^{-7}-10^{-5}$. Experimental searches at $B$ Factories and Hadron Colliders target specific decay modes. Therefore, computing the exclusive branching fraction for each decay is a critical step towards testing Mesogenesis. In this work we use QC…
This work summarizes the current status of the measured semileptonic branching fractions $B^{0,+} \to X_c μν$. The sum of exclusive measurements is compared with the inclusive determination, accounting for isospin extrapolation. Further derived quantities are computed, taking into account different explanations for the unmeasured components of the total branching fraction. These quantities focus on the charge breakdown of the final states, and are designed for use as inputs or comparisons in future experimental measurements.
The most precise measurement of the $CP$ asymmetry in the decay $B^-\rightarrow D_s^-D^0$ has been reported by LHCb collaboration with the value of $(-0.4\pm0.5\pm0.5)\%$. In this study, the $CP$ violation in the decay $B^-\rightarrow D_s^-D^0$ has been calculated under the factorization approach. This decay mode includes current-current tree and penguin diagrams and their amplitudes are considered separately. In each of the tree and penguin amplitudes, the strong and weak phases have been introduced. The $CP$ asymmetry has been calculated in this work to be $(-0.35\pm0.03)\%$. Finally, from t…
We report the first determination of the absolute branching fractions of the X(3872) decays by globally analyzing the measurements provided by the Belle, BaBar, BESIII, and LHCb experiments. The branching fractions of X(3872) to pi^+pi^- J/psi and D*0D0bar+c.c. are found to be (4.1^{+1.9}_{-1.1})% and (52.4^{+25.3}_{-14.3})%, respectively. The branching fractions of the decays X(3872) to gamma J/psi, gamma psi', omega J/psi, and pi^0 chi_{c1} are also determined. The global fit implies that the fraction of X(3872) decays which are not observed in experiments is (31.9_{-31.5}^{+18.1})%, which i…
Current absolute branching fractions of $Λ_c^+$ and $D_s^+$ mesons are limiting the determination of important measurements. They have only been measured at $e^+e^-$ colliders. Here techniques for measuring them at hadron colliders are discussed. The precision determination of $Λ_c^+\to p K^-π^+$ seems possible with current data, however the corresponding determination of $D_s^+\to K^+K^-π^+$ will require more integrated luminosity.
Branching Ratio and CP Violation of B to pi pi Decays in Perturbative QCD Approach
用微扰QCD方法计算了B^0到pi^+pi^-，B^+到pi^+ pi ^0和B^0到pi ^0 pi ^0衰变的分支比和CP不对称性.在这种方法中，我们计算非因式分解和湮灭型的贡献，除了通常的因式分解的贡献。我们发现湮没图的贡献并不像以前的论点那么小。我们的结果与CLEO合作组测得的B对π ^+ π ^-的分支比一致。由于湮灭图和一个大的强相位的不可忽略的贡献，我们预测B^0中的大的直接CP不对称性为pi^+pi^-和pi^0pi^0，这可以通过当前运行的B工厂进行测试。
In this work, we study the localized $CP$ violation and the branching fraction of the four-body decay $\bar{B}^0\rightarrow K^-π^+π^-π^+$ by employing a quasi-two-body QCD factorization approach. Considering the interference of $\bar{B}^0\rightarrow \bar{K}_0^*(700)ρ^0(770)\rightarrow K^-π^+π^-π^+$ and $\bar{B}^0\rightarrow \bar{K}^*(892)f_0(500)\rightarrow K^-π^+π^-π^+$ channels, we predict $\mathcal{A_{CP}}(\bar{B}^0\rightarrow K^-π^+π^-π^+)\in[0.15,0.28]$ and $\mathcal{B}(\bar{B}^0\rightarrow K^-π^+π^-π^+)\in[1.73,5.10]\times10^{-7}$, respectively, which shows that this two channels' interf…
This paper is designed to calculate the branching ratio of four-body decays of $B$ meson with lepton number changed by 2. With the new experimental data limit to lepton-number violation processes, we update the upper limits of mixing parameters between heavy Majorana neutrino and charged leptons. Afterwards, we calculate the branching ratio of $B^0(P)\rightarrow D^{*-}(P_1)\ell^+_1(P_2)\ell^+_2(P_3)M_2^-(P_4)$ using the updated parameters. It is found that the most hopeful decay channel is $B^0(P)\rightarrow D^{*-}(P_1)e^+_1(P_2)e^+_2(P_3)ρ^-(P_4)$ or $B^0(P)\rightarrow D^{*-}(P_1)e(μ)^+_1(P_2…
We consider the one-loop radiative corrections to the light-neutrino mass matrix and their consequences for the predicted branching ratios of the five lepton-flavour-violating decays $\ell_1^- \to \ell_2^- \ell_3^+ \ell_3^-$ in a two-Higgs-doublet model furnished with the type-I seesaw mechanism and soft lepton-flavour violation. We find that the radiative corrections are very significant; they may alter the predicted branching ratios by several orders of magnitude and, in particular, they may help explain why $\mbox{BR}(μ^- \to e^- e^+ e^-)$ is strongly suppressed relative to the branching ra…
The recoil momentum spectrum from the decay $B^+ \to K^+ +\mathrm{anything}$ has recently been measured by the BaBar collaboration. The spectrum has a peak with invariant mass near the mass of the $X(3872)$ meson. The preliminary measurement by the BaBar collaboration implies that its branching fraction into $J/ψ\, π^+π^-$ is about 4\%. We emphasize that this is the branching fraction for the entire resonance feature from $B^+$-to-$K^+$ transitions, which includes a $D^{*0} \bar D^0$ and $D^0 \bar D^{*0}$ threshold enhancement as well as a possible bound state below the threshold or a virtual …
Semileptonic decays $Λ_c^+ \to Λ\ell^+ ν_\ell\,\,(\ell=e,μ)$ in the covariant quark model and comparison with the new absolute branching fraction measurements of Belle and BESIII
The Rate for $e^+e^-\to B B^\pm π^\mp$ and its Implications for the Study of CP Violation, $B_s$ Identification, and the Study of $B$ Meson Chiral Perturbation Theory
Deviation from the standard model prediction is observed in many semileptonic $B$ decays mediated via $b \to c$ charged current interactions. In particular, current experimental measurements of the ratio of branching ratio $R_D$ and $R_{D^{\ast}}$ in $B \rightarrow D^{(*)}l ν$ decays disagree with standard model expectations at the level of about $4.1σ$. Moreover, recent measurement of the ratio of branching ratio $R_{J/Ψ}$ by LHCb, where $R_{J/Ψ} = \mathcal B(B_c \to J/Ψ\,τν)/\mathcal B(B_c \to J/Ψ\,μν)$, is more than $2σ$ away from the standard model prediction. In this context, we consider …
Deviation from the standard model prediction is observed in many semileptonic $B$ decays mediated via $b \to c$ charged current interactions. In particular, current experimental measurements of the ratio of branching ratio $R_D$ and $R_{D^{\ast}}$ in $B \rightarrow D^{(*)}l ν$ decays disagree with standard model expectations at the level of about $4.1σ$. Moreover, recent measurement of the ratio of branching ratio $R_{J/Ψ}$ by LHCb, where $R_{J/Ψ} = \mathcal B(B_c \to J/Ψ\,τν)/\mathcal B(B_c \to J/Ψ\,μν)$, is more than $2σ$ away from the standard model prediction. In this context, we consider …
Lepton Flavour Violation in a Supersymmetric Model with A4 Flavour Symmetry
在味对称群A4 XZ 3 XU（1）_{FN}下的超对称不变量模型中，计算了mu-> e γ，tau-> mu γ和tau -> e γ的分支比，其中近三双峰轻子混合是自然预言的.在小对称性破缺参数u（与反应器混合角theta_{13}同阶）的主导阶，我们发现分支比一般按u ^2标度。对mu -> e γ的分支比应用电流约束表明，对于小于1000 GeV的质量参数m_{SUSY}和m_{1/2}，在模型中u或tan（β）的小值是优选的。从正在进行的MEG实验预期的约束将提供一个严格的约束的参数空间的模型要么强制u约0.01和小tan（β）或m_{SUSY}和m_{1/2}以上1000 GeV。在flavon扇区中的普适软超对称破缺项的特殊情况下，振幅和分支比标度为u^4发生抵消，从而允许较小的slepton质量。预测tau -> mu γ和tau -> e γ的分支比与mu -> e γ的数量级相同，这排除了在不久的将来观察到这些tau衰变的可能性。
The rare top quark decays mediated by a new neutral massive gauge boson that is predicted in models with extended gauge symmetries are studied. We focus on the processes $t\to cV, uV$ induced at the one loop level, where $V =γ, g$, by considering different extended models. It is found that, within a broad range of mass of the new neutral gauge boson, the models predict branching ratios for the decays in study that are competitive with respect to the corresponding branching ratios in the standard model. In order to establish bound on our branching ratios, we consider the recent experimental bou…
