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تسجيل مستخدم جديدRate Measurement of $D^{0}to K^{+}pi^{-}pi^{0}$ and Constraints on $D^{0} - overline{D^{0}}$ Mixing
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We present an observation and rate measurement of the decay D0 -> K+pi-pi0 produced in 9/fb of e+e- collisions near the Upsilon(4S) resonance. The signal is inconsistent with an upward fluctuation of the background by 4.9 standard deviations. We measured the rate of D0 -> K+pi-pi0 normalized to the rate of D0bar -> K+pi-pi0 to be 0.0043 +0.0011 -0.0010 (stat) +/- 0.0007 (syst). This decay can be produced by doubly-Cabibbo-suppressed decays or by the D0 evolving into a D0bar through mixing, followed by a Cabibbo-favored decay to K+pi-pi0. We also found the CP asymmetry A=(8 +25 -22)% to be consistent with zero.
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The first observation of the decay $B^0 rightarrow D^0 overline{D}{}^0 K^+ pi^-$ is reported using proton-proton collision data corresponding to an integrated luminosity of 4.7 $mathrm{fb}^{-1}$ collected by the LHCb experiment in 2011, 2012 and 2016
. The measurement is performed in the full kinematically allowed range of the decay outside of the $D^{*-}$ region. The ratio of the branching fraction relative to that of the control channel $B^0 rightarrow D^{*-} D^0 K^+$ is measured to be $mathcal{R} = (14.2 pm 1.1 pm 1.0)%$, where the first uncertainty is statistical and the second is systematic. The absolute branching fraction of $B^0 rightarrow D^0 overline{D}{}^0 K^+ pi^-$ decays is thus determined to be $mathcal{B}(B^0 rightarrow D^0 overline{D}{}^0 K^+ pi^-) = (3.50 pm 0.27 pm 0.26 pm 0.30) times 10^{-4}$, where the third uncertainty is due to the branching fraction of the control channel. This decay mode is expected to provide insights to spectroscopy and the charm-loop contributions in rare semileptonic decays.
Using a data sample corresponding to 13.7 fb^-1 collected with the CLEO II and II.V detectors, we report new branching fraction measurements for two Cabibbo-suppressed decay modes of the D^+ meson: Br(D^+ to pi^+ pi^0) = (1.3 +/- 0.2) x 10^-3 and Br(
D^+ to bar{K}^0 K^+) = (5.2 +/- 0.6) x 10^-3 which are significant improvements over past measurements. The errors include statistical and systematical uncertainties as well as the uncertainty in the absolute D^+ branching fraction scale. We also set the first 90% confidence level upper limit on the branching fraction of the doubly Cabibbo-suppressed decay mode Br(D^+ to K^+ pi^0) < 4.2 x 10^-4.
We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of $D^0to K^+pi^-$ to $D^0to K^-pi^+$ rates. The analysis uses a data sample of proton-proton collisions corresponding to an integrated luminosity of $5.0$ fb$^
{-1}$ recorded by the LHCb experiment from 2011 through 2016. Assuming charge-parity (CP) symmetry, the mixing parameters are determined to be $x^2=(3.9 pm 2.7) times10^{-5}$, $y=(5.28 pm 0.52) times 10^{-3}$, and $R_D=(3.454 pm 0.031)times10^{-3}$. Without this assumption, the measurement is performed separately for $D^0$ and $overline{D}{}^0$ mesons, yielding a direct CP-violating asymmetry $A_D =(-0.1pm9.1)times10^{-3}$, and magnitude of the ratio of mixing parameters $1.00< |q/p| <1.35$ at the $68.3%$ confidence level. All results include statistical and systematic uncertainties and improve significantly upon previous single-measurement determinations. No evidence for CP violation in charm mixing is observed.
Simulation studies are performed to assess the sensitivity of a model-independent analysis of the flavour-tagged decays $D^0 to K^0_{rm S}pi^+pi^-$ and $D^0 to K^0_{rm S}K^+K^-$ to mixing and CP violation. The analysis takes as input measurements of
the $D$ decay strong-phase parameters that are accessible in quantum-correlated $D-bar{D}$ pairs produced at the $psi(3770)$ resonance. It is shown that the model-independent approach is well suited to the very large data sets expected at an upgraded LHCb experiment, or future high luminosity $e^+e^-$ facility, and that with 100M $K^0_{rm S}pi^+pi^-$ decays a statistical precision of around 0.01 and $0.7^circ$ is achievable on the CP violation parameters $r_{CP}$ and $a_{CP}$, respectively. Even with this very large sample the systematic uncertainties associated with the strong-phase parameters will not be limiting, assuming that full use is made of the available $psi(3770)$ data sets of CLEO-c and BES-III. Furthermore, it is demonstrated that large flavour-tagged samples can themselves be exploited to provide information on the strong-phase parameters, a feature that will be beneficial in the measurement of the CKM angle $gamma/phi_3$ with $B^- to DK^-$ decays.
We present the results of a Dalitz plot analysis of D^0 to K^0_S pi^0 pi^0 using the CLEO-c data set of 818 inverse pico-barns of e^+ e^- collisions accumulated at sqrt{s} = 3.77 GeV. This corresponds to three million D^0 D^0-bar pairs from which we
select 1,259 tagged candidates with a background of 7.5 +- 0.9 percent. Several models have been explored, all of which include the K^*(892), K^*_2(1430), K^*(1680), the f_0(980), and the sigma(500). We find that the combined pi^0 pi^0 S-wave contribution to our preferred fit is (28.9 +- 6.3 +- 3.1)% of the total decay rate while D^0 to K^*(892)^0 pi^0 contributes (65.6 +- 5.3 +- 2.5)%. Using three tag modes and correcting for quantum correlations we measure the D^0 to K^0_S pi^0 pi^0 branching fraction to be (1.059 +- 0.038 +- 0.061)%.
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