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Register a new userMeasurement of $CP$ asymmetry in $D^0 rightarrow K^- K^+$ and $D^0 rightarrow pi^- pi^+$ decays
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Time-integrated $CP$ asymmetries in $D^0$ decays to the final states $K^- K^+$ and $pi^- pi^+$ are measured using proton-proton collisions corresponding to $3mathrm{,fb}^{-1}$ of integrated luminosity collected at centre-of-mass energies of $7mathrm{,Tekern -0.1em V}$ and $8mathrm{,Tekern -0.1em V}$. The $D^0$ mesons are produced in semileptonic $b$-hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. The difference in $CP$ asymmetries between the two final states is measured to be begin{align} Delta A_{CP} = A_{CP}(K^-K^+)-A_{CP}(pi^-pi^+) = (+0.14 pm 0.16mathrm{,(stat)} pm 0.08mathrm{,(syst)})% . onumber end{align} A measurement of $A_{CP}(K^-K^+)$ is obtained assuming negligible $CP$ violation in charm mixing and in Cabibbo-favoured $D$ decays. It is found to be begin{align} A_{CP}(K^-K^+) = (-0.06 pm 0.15mathrm{,(stat)} pm 0.10mathrm{,(syst)}) % , onumber end{align} where the correlation coefficient between $Delta A_{CP}$ and $A_{CP}(K^-K^+)$ is $rho=0.28$. By combining these results, the $CP$ asymmetry in the $D^0rightarrowpi^-pi^+$ channel is $A_{CP}(pi^-pi^+)=(-0.20pm0.19mathrm{,(stat)}pm0.10mathrm{,(syst)})%$.
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A search for CP violation in $D^0 rightarrow K^{-} K^{+} $ and $D^0 rightarrow pi^{-} pi^{+} $ decays is performed using $pp$ collision data, corresponding to an integrated luminosity of $3~fb^{-1}$, collected using the LHCb detector at centre-of-mass energies of 7 and $8~$TeV. The flavour of the charm meson is inferred from the charge of the pion in $D^{*+}rightarrow D^0pi^+$ and $D^{*-}rightarrow bar{D^0}pi^{-}$ decays. The difference between the CP asymmetries in $D^0 rightarrow K^{-} K^{+} $ and $D^0 rightarrow pi^{-} pi^{+} $ decays, $Delta A_{CP} equiv A_{CP}(K^{-} K^{+}) - A_{CP}(pi^{-} pi^{+})$, is measured to be $left( -0.10 pm 0.08(stat) pm 0.03(syst) right) %$. This is the most precise measurement of a time-integrated CP asymmetry in the charm sector from a single experiment.
An analysis of the decays of $B^mp rightarrow D K^mp$ and $B^mp rightarrow D pi^mp $ is presented in which the $D$ meson is reconstructed in the three-body final states $K^mp pi^pm pi^0$, $pi^+ pi^- pi^0$ and $K^+ K^- pi^0$. Using data from LHCb corresponding to an integrated luminosity of 3.0 fb$^{-1}$ of $pp$ collisions, measurements of several $CP$ observables are performed. First observations are obtained of the suppressed ADS decay $B^mp rightarrow [pi^mp K^pm pi^0]_D pi^mp$ and the quasi-GLW decay $B^mp rightarrow [K^+ K^- pi^0]_D pi^mp$. The results are interpreted in the context of the unitarity triangle angle $gamma$ and related parameters.
A model-dependent amplitude analysis of the decay $B^0rightarrow D(K^0_Spi^+pi^-) K^{*0}$ is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0fb$^{-1}$, recorded at $sqrt{s}=7$ and $8 TeV$ by the LHCb experiment. The CP violation observables $x_{pm}$ and $y_{pm}$, sensitive to the CKM angle $gamma$, are measured to be begin{eqnarray*} x_- &=& -0.15 pm 0.14 pm 0.03 pm 0.01, y_- &=& 0.25 pm 0.15 pm 0.06 pm 0.01, x_+ &=& 0.05 pm 0.24 pm 0.04 pm 0.01, y_+ &=& -0.65^{+0.24}_{-0.23} pm 0.08 pm 0.01, end{eqnarray*} where the first uncertainties are statistical, the second systematic and the third arise from the uncertainty on the $Drightarrow K^0_S pi^+pi^-$ amplitude model. These are the most precise measurements of these observables. They correspond to $gamma=(80^{+21}_{-22})^{circ}$ and $r_{B^0}=0.39pm0.13$, where $r_{B^0}$ is the magnitude of the ratio of the suppressed and favoured $B^0rightarrow D K^+ pi^-$ decay amplitudes, in a $Kpi$ mass region of $pm50 MeV$ around the $K^*(892)^0$ mass and for an absolute value of the cosine of the $K^{*0}$ decay angle larger than $0.4$.
The branching fractions of the doubly Cabibbo-suppressed decays $D^+rightarrow K^-K^+K^+$, $D^+rightarrow pi^-pi^+K^+$ and $D^+_srightarrowpi^-K^+K^+$ are measured using the decays $D^+rightarrow K^-pi^+pi^+$ and $D^+_srightarrow K^-K^+pi^+$ as normalisation channels. The measurements are performed using proton-proton collision data collected with the LHCb detector at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2.0 fb$^{-1}$. The results are begin{align} frac {mathcal{B}(D^+rightarrow K^-K^+K^+)} {mathcal{B}(D^+rightarrow K^-pi^+pi^+)}& = (6.541 pm 0.025 pm 0.042) times 10^{-4}, onumber frac {mathcal{B}(D^+rightarrow pi^-pi^+K^+)} {mathcal{B}(D^+rightarrow K^-pi^+pi^+)}& = (5.231 pm 0.009 pm 0.023) times 10^{-3}, onumber frac {mathcal{B}(D^+_srightarrowpi^-K^+K^+)} {mathcal{B}(D^+_srightarrow K^-K^+pi^+)}& = (2.372 pm 0.024 pm 0.025) times 10^{-3}, onumber end{align} where the uncertainties are statistical and systematic, respectively. These are the most precise measurements up to date.
We present an amplitude analysis of the decay $D^{0} rightarrow K^{-} pi^{+} pi^{+} pi^{-}$ based on a data sample of 2.93 ${mbox{,fb}^{-1}}$ acquired by the BESIII detector at the $psi(3770)$ resonance. With a nearly background free sample of about 16000 events, we investigate the substructure of the decay and determine the relative fractions and the phases among the different intermediate processes. Our amplitude model includes the two-body decays $D^{0} rightarrow bar{K}^{*0}rho^{0}$, $D^{0} rightarrow K^{-}a_{1}^{+}(1260)$ and $D^{0} rightarrow K_{1}^{-}(1270)pi^{+}$, the three-body decays $D^{0} rightarrow bar{K}^{*0}pi^{+}pi^{-}$ and $D^{0} rightarrow K^{-}pi^{+}rho^{0}$, as well as the four-body decay $D^{0} rightarrow K^{-}pi^{+}pi^{+}pi^{-}$. The dominant intermediate process is $D^{0} rightarrow K^{-}a_{1}^{+}(1260)$, accounting for a fit fraction of $54.6%$.
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