arXiv subjects
Publications and source records attributed to Chuan-Hung Chen.
We study the T violating effects in the baryonic decays of $Λ_b\toΛl^+l^- (l=e ,μ)$ with polarized $Λ$. We show that the transverse $Λ$ polarizations in these baryonic decays could be as large as 50% in CP violating theories beyond the standard model such as the SUSY models, which can be tested in various future hadron colliders.
We show that in the PQCD approach the $B\to ρ(ω) K$ decays display not only the dynamical penguin enhancement, the mechanism responsible for the large branching ratios (BRs) of $B\to ϕK$ decays, but also the importance of annihilation contributions. We find that the CP asymmetries (CPAs) of $B\to ρ^{\pm}K^{\mp}$, $B^{\mp}\to ρ^0(ω)K^{\mp}$ (class I) are all over 50%.
We show that a large CP asymmetry in hyperon decays can be naturally realized in the framework of SUSY models. The possibility is implemented by the hermiticities of Yukawa and A matrices. And also, the observed values of $ε$ and $ε'$ are explained.
We study $B_{s}\to KK$ decays in the framework of the PQCD. We show that the branching ratios of $B_{s}\to (K^+ K^-, K^0 \bar{K}^0)$ are about $(22.43, 25.78) \times 10^{-6}$ for $ϕ_{3}(γ)\simeq72^0$, which are consistent with the model-independent estimations. We find that the typical scale of the decays is near 1.7 GeV. We also point out that the induced strong phase $δ$ is around $207^0$ so that the direct CP asymmetry of $B_{s}\to K^+K^-$ could reach 15%.
We investigate exclusive nonleptonic $B$ meson decays $B\toϕK$ in perturbative QCD formalism. It is shown that the end-point (logarithmic and linear) singularities in decay amplitudes do not exist, after $k_T$ and threshold resummations are included. Power counting for emission and annihilation topologies of diagrams, including both factorizable and nonfactorizable ones, is discussed with Sudakov effects taken into account. Our predictions for the branching ratios $B(B\toϕK)\sim 10 \times 10^{-6}$ are larger than those ($\sim 4 \times 10^{-6}$) from the factorization approach because of dynamical enhancement of penguin contributions. Whether this enhancement is essential for penguin-dominated modes can be justified by experimental data.
We explored various cases for the branching ratios (BRs) of $B_s\to K^+K^-$, $B_s\to K^0\bar{K}^0$ and $B_d\to π^+ π^-$ decays. We study the possibility of determining $γ$ by using the following the measurements: (a) BRs of $B_s\to K^+K^-$, and $B_s\to K^0\bar{K}^0$; (b) the ratio of direct CP asymmetries in $B_d\to π^+ π^-$ and $B_s\to K^+K^-$; (c) the mix-induced CP asymmetry in $B_d\to π^+ π^-$; and (d) the angle of $β$.
We present a systematic analysis for the rare baryonic exclusive decays of $Λ_b\toΛl^+ l^- (l=e,μ,τ)$. We study the differential decay rates and the di-lepton forward-backward, lepton polarization and various CP asymmetries with a new simple set of form factors inspired by the heavy quark effective theory. We show that most of the observables are insensitive to the non-perturbative QCD effects. To illustrate the effect of new physics, we discuss our results in an explicit supersymmetric extension of the standard model, which contains new CP violating phases and therefore induces sizable CP violating asymmetries.
We study the contribution of a generic charged Higgs $(H^+)$ to the muon anomalous magnetic moment $a_μ$ with the SUSY soft breaking parameters. We find out that the deviation between the experimental data and the predicted SM value on $a_μ$ can be explained by the two-loop charged Higgs diagrams even with $m_{H^+}\sim 400 GeV$.
We study the dilepton forward-backward and the longitudinal, normal and transverse lepton polarization asymmetries in the heavy baryon decays of $Λ_b\toΛl^+l^-$. We show that the asymmetries have a less dependence on the non-perturbative QCD effects. In the standard model, we find that the integrated forward-backward asymmetries (FBAs) and three components of the polarizations in the QCD sum rule approach (pole model) are $-0.13\ (-0.12)$ and $(58.3,-9.4,-0.07)%$ ($(58.3,-12.6,-0.07)%$) for $Λ_b\toΛμ^+μ^-$ and $-0.04 (-0.03)$ and $(10.9,-10.0,-0.39)%$ ($(10.9,-0.2,-0.34)%$) for $Λ_b\toΛτ^+τ^-$, respectively.
We investigate the rare baryonic exclusive decays of $Λ_b\to Λl^+ l^- (l=e,μ,τ)$ with polarized $Λ$. Under the approximation of the heavy quark effective theory (HQET), in the standard model we derive the differential decay rates and various polarization asymmetries by including lepton mass effects. We find that with the long-distance effects the decay branching ratios are $5.3\times 10^{-5}$ for $Λ_b\to Λl^+ l^-\ (l=e,μ)$ and $1.1\times 10^{-5}$ for $Λ_b\to Λτ^+τ^-$. The effects of new physics in the decay rates are also discussed. The integrated longitudinal $Λ$ polarizations are -0.31 and -0.12, while that of the normal ones 0.02 and 0.01, for di-muon and tau modes, respectively. The CP-odd transverse polarization of $Λ$ is zero in the standard model but it is expected to be sizable in some theories with new physics.
We study the exclusive decays of $B\to K^{(*)}l^+l^-$ within the framework of the PQCD. We obtain the form factors for the $B\to K^{(*)}$ transitions in all allowed values of $q^2$, which agree with the lattice results. We find that our distributions of the decay rates and leptonic asymmetries are consistent with that given in the other QCD models in the literature.
We investigate the decay of $Λ_b\toΛν\barν$ with the polarized baryons of $Λ_b$ and $Λ$. With the most general hadronic form factors, we first study the decay branching ratio and then derive the longitudinal, normal and transverse polarizations of $Λ$ in terms of the spin unit vectors of $Λ_b$ and $Λ$ and the momentum of $Λ$. A polarization of $Λ_b$ is also discussed.
We predict branching ratios and CP asymmetries of the $B\to KK$ decays using perturbative QCD factorization theorem, in which tree, penguin, and annihilation contributions, including both factorizable and nonfactorizable ones, are expressed as convolutions of hard six-quark amplitudes with universal meson wave functions. The unitarity angle $ϕ_3= 90^o$ and the $B$ and $K$ meson wave functions extracted from experimental data of the $B\to Kπ$ and $ππ$ decays are employed. Since the $B\to KK$ decays are sensitive to final-state-interaction effects, the comparision of our predictions with future data can test the neglect of these effects in the above formalism. The CP asymmetry in the $B^\pm\to K^\pm K^0$ modes and the $B_d^0\to K^\pm K^\mp$ branching ratios depend on annihilation and nonfactorizable amplitudes. The $B\to KK$ data can also verify the evaluation of these contributions.
The CP properties in hyperon decays are briefly reviewed. We discuss the general phenomenology and define CP odd observables in hyperon decays. With these observables, we discuss the predictions of some models and their observational potential.