New Physics signature in $D^0 (bar{D}^0)to f$ effective width asymmetries

Violation of charge conjugation-parity ($rm CP$) symmetry plays a major rule in the dominance of matter in our universe. A kind of $rm CP$ violation results from the asymmetry of the life time measured in $M^0$ and $bar M^0$, here $M$ is a heavy meson, decays to final states which is referred in the literature as $A_{Gamma}^f$. In this paper, we give an estimation of the upper bound on $|A_{Gamma}^f|$ for the Cabibbo Favored $D^0 rightarrow K^- pi^+$ decay process in different models. We show that in the standard model, $|A_{Gamma}^f| lesssimmathcal{O} (10^{-10})$. Recently a bound on $A_{Gamma}^f$ has been obtained: $(A^f_{Gamma})^{Exp.}= (1.6 pm 1)times 10^{-4}$. This result motivates further studies on $A_{Gamma}^f$ in beyond standard model physics. In the framework of two Higgs doublet model with generic Yukawa structure, we show that $|A_Gamma^{f}|lesssim mathcal{O} (10^{-7})$ which is several orders of magnitude smaller than the current experimental value. Finally, in the framework of left-right symmetric models in which the mixing between the left and the right gauge bosons is allowed and the left-right symmetry is not manifest at unification scale, we find that $A_{Gamma}^f$ can be as large as $|A_{Gamma}^f|lesssimmathcal{O} (10^{-5})$ which is one order of magnitude smaller than the experimentally measured value by LHCb collaborators.

New Physics effects in D^+ rightarrow K^- pi^+ pi^+

In this paper, we study the Cabibbo favored three body non-leptonic D^+ rightarrow K^- pi^+ pi^+ decay. We show that the corresponding direct CP asymmetry is so tiny in the framework of the Standard Model and is out of the experimental range. Motivated by this result we extend the study of the CP asymmetry to include a toy model with CP violating weak phase equals 20 degrees in a_2, a model with extra gauge bosons within Left-Right Grand Unification models and a model with charged Higgs boson. We show that the toy model can strongly improve the SM prediction of the CP asymmetry to be about 30%. The largest CP asymmetry can be achieved in the non-manifest Left-Right models where a CP asymmetry up to 25% can be reached. For the two Higgs doublets models the CP asymmetry is of order 10^{-3}.

Observation of CP violation in $D^0 rightarrow K^- pi^+ $ as a smoking gun for New Physics

In this paper, we study the Cabibbo favored non-leptonic $D^0$ decays into $K^- pi^+$ decays. First we show that, within the Standard Model, the corresponding CP asymmetry is strongly suppressed and out of the experimental range even taking into account the large strong phases coming from final state Interactions. We show also that although new physics models with extra sequential generation can enhance the CP asymmetry by few orders of magnitude however the resulting CP asymmetry is still far from experimental range. The most sensitive New Physics Models to this CP asymmetry comes from no-manifest Left-Right models where a CP asymmetry up to 10% can be reached and general two Higgs models extension of SM where a CP asymmetry of order $10^{-2}$ can be obtained without being in contradiction with the experimental constraints on these models.