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Register a new userExploring new physics contributions to $CP$ violation in $tau^- to K^-pi^0 u_{tau} $
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A general analysis of possible violation of CP in processes like $tau to Kpi u$, for unpolarized $tau$ is presented. In this paper, we derive the new contributions to the effective Hamiltonian governs $vertDelta S vert=1$ semileptonic tau decays in the framework of two Higgs doublet model with generic Yukawa structure and Leptoquarks models. Within these models, we list all operators, in the effective Hamiltonian and provide analytical expression for their corresponding Wilson coefficients. Moreover, we analyze the role of the different contributions, originating from the scalar, vecor and tensor hadronic currents, in generating direct CP asymmetry in the decay rate of $tau^-to K^-pi^0 u_tau$. We show that non vanishing direct CP asymmetry in the decay rate of $tau^-to K^-pi^0 u_tau$ can be generated due to the presence of both, the weak phase in the Wilson coefficient corresponding to the tensor operator and the strong phase difference resulting from the interference between the form factors expressing the matrix elements of the vector and tensor hadronic currents. After taking into account all relevant constraints, we find that the generated direct CP asymmetry is of order $10^{-8}$ which is several orders of magnitude larger than the standard model prediction. We show also that, in two Higgs doublet model with generic Yukawa structure , direct local or non integrated CP violation can be as large as $0.3$ % not far from experimental possibilities. This kind of asymmetry can be generated due to the interference between vector and scalar contributions with different weak phases which is not the case in the SM.
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The potential of performing a combined analysis of the strangeness-changing decays $tau^{-}to K_{S}pi^{-} u_{tau}$ and $tau^{-}to K^{-}eta u_{tau}$ for unveiling the $K^{*}(1410)$ resonance pole parameters is illustrated. Our study is carried out within the framework of Chiral Perturbation Theory, including resonances as explicit degrees of freedom. Resummation of final state interactions are considered through a dispersive parameterization of the required form factors. A considerable improvement in the determination of the pole position with mass $M_{K^{*}(1410)}=1304pm17$ MeV and width $Gamma_{K^{*}(1410)}=171pm62$ MeV is obtained.
We report a feasibility study of $CP$ violation of $tau^{-}rightarrow K_{S}pi^{-} u_{tau}$ decay at a Super Tau Charm Facility~(STCF).With an expected luminosity of 1~ab$^{-1}$ collected by STCF per year at a center-of-mass energy of 4.26 GeV, the statistical sensitivity for the $CP$ violation is determined to be of order $9.7times10^{-4}$ by measuring the decay-rate difference between $tau^{+}rightarrow K_{S}pi^{+}bar{ u}_{tau}$ and $tau^{-}rightarrow K_{S}pi^{-} u_{tau}$. The analysis is performed using a reliable fast simulation software package, which can describe the detector responses properly and vary the responses flexibly for further optimization. Moreover, the energy-dependent efficiencies for reconstructing $tau^{-}rightarrow K_{S}pi^{-} u_{tau}$ are presented and the expected $CP$ sensitivity is proportional to $1/sqrt{mathcal{L}}$ in the energy region from 4.0 to 5.0 GeV. The sensitivity of $CP$ violation is of order $3.1times10^{-4}$ with 10~ab$^{-1}$ integrated luminosity, which is equivalent to ten years data taking in this energy region at STCF.
In this paper we study the direct CP asymmetry of the doubly Cabibbo-suppressed decay mode $D^0 to K^+ pi^- $ within standard model and two Higgs doublet model with generic Yukawa structure. In the standard model we derive the corrections to the tree level amplitude, generated from the box and di-penguin diagrams, required for generating the weak CP violating phases. We show that these phases are so tiny leading to a direct CP asymmetry of order $10^{-9}$. Regarding the two Higgs doublet model with generic Yukawa structure we derive the Wilson coefficients relevant to $D^0 to K^+ pi^- $. After taking into account all constraints on the parameter space of the model we show that charged Higgs couplings to quarks can lead to a direct CP asymmetry of order $10^{-3}$ which is $6$ orders of magnitude larger than the standard model prediction.
Present experimental datas have shown a 3.8$sigma$ level discrepancy with the standard model in $overline{B}to D^{(*)}taubar{ u}_{tau}$. Some new physics models have been considered to explain this discrepancy possibly with new source of the CP violation. In this paper, we construct CP violating observables by using multi-pion decays in $Bto Dtau u_{tau}$, and estimate sensitivity of these observables to generic CP violating operators. We also discuss possibilities of CP violation in leptoquark models and in 2HDM of type-III.
In this paper we investigate CP violation in charged decays of $D$ meson. Particularly, we study the direct CP asymmetry of the Cabibbo favored non-leptonic $D^+ rightarrow bar K^0 pi^+$ and the doubly Cabibbo-suppressed decay mode $D^+ rightarrow K^0 pi^+$ within standard model, two Higgs doublet model with generic Yukawa structure and left right symmetric models. In the standard model, we first derive the contributions from box and di-penguin diagrams contributing to their amplitudes which are relevant to the generation of the weak phases essential for non-vanishing direct CP violation. Then, we show that these phases are so tiny leading to a direct CP asymmetry of order $10^{-11}$ in both decay modes. Regarding the two Higgs doublet model with generic Yukawa structure and after taking into account all constraints on the parameter space of the model, we show that the enhanced direct CP asymmetries can be 6 and 7 orders of magnitudes larger than the standard model prediction for $D^+ rightarrow bar K^0 pi^+$ and $D^+ rightarrow K^0 pi^+$ respectively. Finally, within left right symmetric models, we find that sizable direct CP asymmetry of ${mathcal O } (10^{-3})$ can be obtained for the decay mode $D^+ rightarrow bar K^0 pi^+$ after respecting all relevant constraints.
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