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Register a new userObservation of $D^{0(+)}to K^0_Spi^{0(+)}eta^prime$ and improved measurement of $D^0to K^-pi^+eta^prime$
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By analyzing $2.93 rm fb^{-1}$ of data taken at a center-of-mass energy of 3.773~GeV with the BESIII detector, we measure the branching fractions of the Cabibbo-favored hadronic decays $D^0to K^-pi^+eta^prime$, $D^0to K^0_Spi^0eta^prime$ and $D^+to K^0_Spi^+eta^prime$, which are determined to be $(6.43 pm 0.15_{rm stat.} pm 0.31_{rm syst.})times 10^{-3}$, $(2.52 pm 0.22_{rm stat.} pm 0.15_{rm syst.})times 10^{-3}$ and $(1.90 pm 0.17_{rm stat.} pm 0.13_{rm syst.})times 10^{-3}$, respectively. The precision of the branching fraction of $D^0to K^-pi^+eta^prime$ is significantly improved, and the processes $D^0to K^0_Spi^0eta^prime$ and $D^+to K^0_Spi^+eta^prime$ are observed for the first time.
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Using a sample of $1.3times 10^9$ $J/psi$ events collected with the BESIII detector, we report the first observation of $eta^{prime}topi^{+}pi^{-}pi^{+}pi^{-}$ and $eta^{prime}topi^{+}pi^{-}pi^{0}pi^{0}$. The measured branching fractions are $mathcal{B}$($eta^{prime}topi^{+}pi^{-}pi^{+}pi^{-}$) = $(8.53pm0.69({rm stat.})pm0.64({rm syst.}))times10^{-5}$ and $mathcal{B}$($eta^{prime}topi^{+}pi^{-}pi^{0}pi^{0}$) = $(1.82pm0.35({rm stat.})pm0.18({rm syst.}))times10^{-4}$, which are consistent with theoretical predictions based on a combination of chiral perturbation theory and vector-meson dominance.
We measure the branching fractions and $CP$ asymmetries for the singly Cabibbo-suppressed decays $D^{0}topi^{+}pi^{-}eta$, $D^{0}to K^{+}K^{-}eta$, and $D^{0}tophieta$, using 980 fb$^{-1}$ of data from the Belle experiment at the KEKB $e^+e^-$ collider. We obtain begin{eqnarray} mathcal{B}(D^{0}topi^{+}pi^{-}eta) & = & [1.22pm 0.02,({rm stat})pm 0.02,({rm syst})pm 0.03,(mathcal{B}_{rm ref})]times 10^{-3},, onumber mathcal{B}(D^{0}to K^{+}K^{-}eta) & = & [1.80,^{+0.07}_{-0.06},({rm stat})pm 0.04,({rm syst})pm 0.05,(mathcal{B}_{rm ref})]times 10^{-4},, onumber mathcal{B}(D^{0}tophieta) & = & [1.84pm 0.09,({rm stat})pm 0.06,({rm syst})pm 0.05,(mathcal{B}_{rm ref})]times 10^{-4},, onumber end{eqnarray} where the third uncertainty ($mathcal{B}_{rm ref}$) is from the uncertainty in the branching fraction of the reference mode $D^{0}to K^{-}pi^{+}eta$. The color-suppressed decay $D^{0}tophieta$ is observed for the first time, with very high significance. The results for the $CP$ asymmetries are begin{eqnarray} A_{CP}(D^{0}topi^{+}pi^{-}eta) & = & [0.9pm 1.2,({rm stat})pm 0.5,({rm syst})]%,, onumber A_{CP}(D^{0}to K^{+}K^{-}eta) & = & [-1.4pm 3.3,({rm stat})pm 1.1,({rm syst})]%,, onumber A_{CP}(D^{0}tophieta)&= & [-1.9pm 4.4,({rm stat})pm 0.6,({rm syst})]%,. onumber end{eqnarray} The results for $D^{0}topi^{+}pi^{-}eta$ are a significant improvement over previous results. The branching fraction and $A_{CP}$ results for $D^{0}to K^{+}K^{-}eta$, and the $A_{CP}$ result for $D^{0}tophieta$, are the first such measurements. No evidence for $CP$ violation is found in any of these decays.
An experimental study of the $etato pi^0pi^0eta to 6gamma$ decay has been conducted with the best up-to-date statistical accuracy, by measuring $eta$ mesons produced in the $gamma p to eta p$ reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The results obtained for the standard parametrization of the $etato pi^0pi^0eta$ matrix element are consistent with the most recent results for $etatopipieta$ decays, but have smaller uncertainties. The available statistics and experimental resolution allowed, for the first time, an observation of a structure below the $pi^+pi^-$ mass threshold, the magnitude and sign of which, checked within the framework of the nonrelativistic effective-field theory, demonstrated good agreement with the cusp that was predicted based on the $pipi$ scattering length combination, $a_0-a_2$, extracted from $K to 3pi$ decays.
By analyzing a data sample of 2.93 fb$^{-1}$ collected at $sqrt s=$ 3.773 GeV with the BESIII detector operated at the BEPCII storage rings, we measure the branching fractions ${mathcal B}(D^0toomegaeta)=(2.15pm0.17_{rm stat.}pm0.15_{rm sys.})times 10^{-3}$, ${mathcal B}(D^0toetapi^0)=(0.58pm0.05_{rm stat.}pm0.05_{rm sys.})times 10^{-3}$, ${mathcal B}(D^0toeta^primepi^0)=(0.93pm0.11_{rm stat.}pm0.09_{rm sys.})times 10^{-3}$, ${mathcal B}(D^0toetaeta)=(2.20pm0.07_{rm stat.}pm0.06_{rm sys.})times 10^{-3}$ and ${mathcal B}(D^0toeta^primeeta)=(0.94pm0.25_{rm stat.}pm0.11_{rm sys.})times 10^{-3}$. We note that ${mathcal B}(D^0to omegaeta)$ is measured for the first time and that ${mathcal B}(D^0to etaeta)$ is measured with much improved precision.
Charm meson oscillations are observed in a time-dependent analysis of the ratio of $D^0to K^+pi^-pi^+pi^-$ to $D^0to K^-pi^+pi^-pi^+$ decay rates, using data corresponding to an integrated luminosity of $3.0,{rm fb}^{-1}$ recorded by the LHCb experiment. The measurements presented are sensitive to the phase-space averaged ratio of doubly Cabibbo-suppressed to Cabibbo-favoured amplitudes $r_{D}^{K3pi}$ and the product of the coherence factor $R_{D}^{K3pi}$ and a charm mixing parameter $y^{}_{K3pi}$. The constraints measured are $r_{D}^{K3pi}=(5.67 pm 0.12)times10^{-2}$, which is the most precise determination to date, and $R_{D}^{K3pi} cdot y^{}_{K3pi} = (0.3 pm 1.8)times 10^{-3}$, which provides useful input for determinations of the CP-violating phase $gamma$ in $B^pm to D K^pm, D to K^mppi^pmpi^mppi^pm$ decays. The analysis also gives the most precise measurement of the $D^0to K^+pi^-pi^+pi^-$ branching fraction, and the first observation of $D^0-bar D^0$ oscillations in this decay mode, with a significance of 8.2 standard deviations.
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