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Register a new userMeasurement of the charm-mixing parameter $y_{CP}$
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A measurement of the charm-mixing parameter $y_{CP}$ using $D^0 to K^+ K^-$, $D^0 to pi^+ pi^-$, and $D^0 to K^- pi^+$ decays is reported. The $D^0$ mesons are required to originate from semimuonic decays of $B^-$ and $overline{B}^0$ mesons. These decays are partially reconstructed in a data set of proton-proton collisions at center-of-mass energies of 7 and 8 TeV collected with the LHCb experiment and corresponding to an integrated luminosity of 3 fb$^{-1}$. The $y_{CP}$ parameter is measured to be $(0.57 pm 0.13(rm{stat.}) pm 0.09(rm{syst.}))%$, in agreement with, and as precise as, the current world-average value.
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We report the first measurement of the charm-mixing parameter $y_{CP}$ in $D^{0}$ decays to the $CP$-odd final state $K^{0}_{S}omega$. The study uses the full Belle $e^{+}e^-$ annihilation data sample of $976rm~ fb^{-1}$ taken at or near the $Upsilon(4S)$ centre-of-mass energy. We find $y_{CP} = (0.96 pm 0.91 pm 0.61 {}^{+0.17}_{-0.00})%$, where the first uncertainty is statistical, the second is systematic due to event selection and background, and the last is due to possible presence of $CP$-even decays in the data sample.
A study of mixing and indirect CP violation in D0 mesons through the determination of the parameters y_CP and A_Gamma is presented. The parameter y_CP is the deviation from unity of the ratio of effective lifetimes measured in D0 decays to the CP eigenstate K+K- with respect to decays to the Cabibbo favoured mode K-pi+. The result measured using data collected by LHCb in 2010, corresponding to an integrated luminosity of 29 pb^-1, is y_CP = (5.5+/-6.3_{stat}+/-4.1_{syst}) x 10^-3. The parameter A_Gamma is the asymmetry of effective lifetimes measured in decays of D0 and anti-D0 mesons to K+K-. The result is A_Gamma = (-5.9+/-5.9_{stat}+/-2.1_{syst}) x 10^-3. A data-driven technique is used to correct for lifetime-biasing effects.
The phenomenon of mixing in neutral meson systems has now been observed in all flavours, but only in the past year in the D0 system. The standard model anticipated that, for the charm sector, the mixing rate would be small, and also that CP violation, either in mixing or in direct decay, would be below the present levels of observability. It is hoped that further study of these phenomena might reveal signs of new physics. A review of recently available, experimental results is given.
We present a summary of recent results on CP violation and mixing in the charm quark sector based on a high statistics sample collected by photoproduction experiment FOCUS (E831 at Fermilab). We have measured the difference in lifetimes for the $D^0$ decays: $D^0 to K^-pi^+$ and $D^0 to K^-K^+$. This translates into a measurement of the $y_{CP}$ mixing parameter in the $d0d0$ system, under the assumptions that $K^-K^+$ is an equal mixture of CP odd and CP even eigenstates, and CP violation is negligible in the neutral charm meson system. We verified the latter assumption by searching for a CP violating asymmetry in the Cabibbo suppressed decay modes $D^+ to K^-K^+pi^+$, $D^0 to K^-K^+$ and $D^0 to pi^-pi^+$. We show preliminary results on a measurement of the branching ratio $Gamma(D^{*+}to pi^+ (K^+pi^-))/Gamma(D^{*+}to pi^+ (K^-pi^+))$.
In recent years charm physics has undergone a renaissance, one which has been catalysed by an unexpected and impressive set of experimental results from the $B$-factories, the Tevatron and LHCb. The existence of $D^0bar{D}{}^0$ oscillations is now well established, and the recent discovery of $CP$ violation in $D^0$ decays has further renewed interest in the charm sector. In this article we review the current status of charm-mixing and $CP$-violation measurements, and assess their agreement with theoretical predictions within the Standard Model and beyond. We look forward to the great improvements in experimental precision that can be expected over the coming two decades, and the prospects for corresponding advances in theoretical understanding.
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