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Register a new userCP violating asymmetries in charged D meson decays
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The CP violating asymmetries for Cabibbo suppressed charged D meson decays in the standard model are estimated in the factorized approximation, using the two-loop effective hamiltonian and a model for final state interactions previously tested for Cabibbo allowed D decays. No new parameters are added. The predictions are larger than expected and not too far from the experimental possibilities.
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We point out that, if the direct CP asymmetries in the $D to pi^+ pi^-$ and $D to K^+ K^-$ decays are unequal, the indirect CP asymmetries as measured in these modes are necessarily unequal. This nonuniversality of indirect CP asymmetries can be significant with the right amount of new physics contributions, a scenario that may be fine-tuned, but is still viable. A model-independent fit to the current data allows different indirect CP asymmetries in the above two decays. This could even be contributing to the apparent tension between the difference CP asymmetries $Delta A_{rm CP}$ measured through the pion-tagged and muon-tagged data samples at the LHCb. This also implies that the measurements of $A_Gamma$ and $y_{rm CP}$ in the $pi^+ pi^-$ and $K^+ K^-$ decay modes can be different, and averaging over these two modes should be avoided. In any case, the complete analysis of CP violation measurements in the $D$ meson sector needs to take into account the possibility of different indirect CP asymmetries in the $pi^+pi^-$ and $K^+ K^-$ channels.
CP asymmetries have been measured recently by the LHCb collaboration in three-body $B^+$ decays to final states involving charged pions and kaons. Large asymmetries with opposite signs at a level of about 60% have been observed in $B^pmto pi^pm({rm or} K^pm)pi^+pi^-$ and $B^pm to pi^pm K^+K^-$ for restricted regions in the Dalitz plots involving $pi^+pi^-$ and $K^+K^-$ with low invariant mass. U-spin is shown to predict corresponding $Delta S=0$ and $Delta S=1$ asymmetries with opposite signs and inversely proportional to their branching ratios, in analogy with a successful relation predicted thirteen years ago between asymmetries in $B_sto K^-pi^+$ and $B^0 to K^+ pi^-$. We compare these predictions with the measured integrated asymmetries. Effects of specific resonant or non-resonant partial waves on enhanced asymmetries for low-pair-mass regions of the Dalitz plot are studied in $B^pm to pi^pm pi^+pi^-$. The closure of low-mass $pi^+pi^-$ and $K^+K^-$ channels involving only $pipi leftrightarrow Kbar K$ rescattering may explain by CPT approximately equal magnitudes and opposite signs measured in $B^pmto pi^pmpi^+pi^-$ and $B^pm to pi^pm K^+K^-$.
We report measurements of branching fractions and time-dependent CP asymmetries in $B^{0} to D^{+}D^{-}$ and $B^{0} to D^{*pm}D^{mp}$ decays using a data sample that contains $(772 pm 11)times 10^6 Bbar{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We determine the branching fractions to be $mathcal{B}(B^{0} to D^{+}D^{-})=(2.12 pm 0.16 pm 0.18)times 10^{-4}$ and $mathcal{B}(B^{0} to D^{*pm}D^{mp}=(6.14 pm 0.29 pm 0.50)times 10^{-4}$. We measure CP asymmetry parameters $mathcal{S}_{D^{+}D^{-}} = -1.06_{-0.14}^{+0.21} pm 0.08$ and $mathcal{C}_{D^{+}D^{-}} = -0.43 pm 0.16 pm 0.05$ in $B^{0} to D^{+}D^{-}$ and $mathcal{A}_{D^{*}D} = +0.06 pm 0.05 pm 0.02$, $mathcal{S}_{D^{*}D} = -0.78 pm 0.15 pm 0.05$, $mathcal{C}_{D^{*}D} = -0.01 pm 0.11 pm 0.04$, $Deltamathcal{S}_{D^{*}D} = -0.13 pm 0.15 pm 0.04$ and $Deltamathcal{C}_{D^{*}D} = +0.12 pm 0.11 pm 0.03$ in $B^{0} to D^{*pm}D^{mp}$, where the first uncertainty is statistical and the second is systematic. We exclude the conservation of CP symmetry in both decays at equal to or greater than $4sigma$ significance.
We report a measurement of the indirect CP-violating asymmetries ($A_{Gamma}$) between effective lifetimes of anticharm and charm mesons reconstructed in $D^0to K^+ K^-$ and $D^0to pi^+pi^-$ decays. We use the full data set of proton-antiproton collisions collected by the Collider Detector at Fermilab experiment and corresponding to $9.7$~fb$^{-1}$ of integrated luminosity. The strong-interaction decay $D^{*+}to D^0pi^+$ is used to identify the meson at production as $D^0$ or $overline{D}^0$. We statistically subtract $D^0$ and $overline{D}^0$ mesons originating from $b$-hadron decays and measure the yield asymmetry between anticharm and charm decays as a function of decay time. We measure $A_Gamma (K^+K^-) = (-0.19 pm 0.15 (stat) pm 0.04 (syst))%$ and $A_Gamma (pi^+pi^-)= (-0.01 pm 0.18 (stat) pm 0.03 (syst))%$. The results are consistent with the hypothesis of CP symmetry and their combination yields $A_Gamma = (-0.12 pm 0.12)%$.
We report final measurements of direct $mathit{CP}$--violating asymmetries in charmless decays of neutral bottom hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. Using the complete $sqrt{s}=1.96$ TeV proton-antiproton collisions data set, corresponding to 9.3 fb$^{-1}$ of integrated luminosity, we measure $mathcal{A}(Lambda^0_b rightarrow ppi^{-}) = +0.06 pm 0.07mathrm{(stat)} pm 0.03mathrm{(syst)}$ and $mathcal{A}(Lambda^0_b rightarrow pK^{-}) = -0.10 pm 0.08mathrm{(stat)} pm 0.04mathrm{(syst)}$, compatible with no asymmetry. In addition we measure the $mathit{CP}$--violating asymmetries in $B^0_s rightarrow K^{-}pi^{+}$ and $B^0 rightarrow K^{+}pi^{-}$ decays to be $mathcal{A}(B^0_s rightarrow K^{-}pi^{+}) = +0.22 pm 0.07mathrm{stat)} pm 0.02mathrm{(syst)}$ and $mathcal{A}(B^0 rightarrow K^{+}pi^{-}) = -0.083pm 0.013 mathrm{(stat)} pm 0.004mathrm{(syst)}$, respectively, which are significantly different from zero and consistent with current world averages.
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