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Register a new userMeasurement of the matrix elements for the decays $eta^{prime}rightarrowetapi^+pi^-$ and $eta^{prime}rightarrowetapi^0pi^0$
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Based on a sample of $1.31times10^9$ $J/psi$ events collected with the BESIII detector, the matrix elements for the decays $eta^{prime}toetapi^{+}pi^{-}$ and $eta^{prime}toeta pi^{0}pi^{0}$ are determined using 351,016 $eta^{prime}to(etatogammagamma)pi^+pi^-$ and 56,249 $eta^{prime}to(etatogammagamma)pi^0pi^0$ events with background levels less than 1%. Two commonly used representations are used to describe the Dalitz plot density. We find that an assumption of a linear amplitude does not describe the data well. A small deviation of the obtained matrix elements between $eta^{prime}toetapi^{+}pi^{-}$ and $eta^{prime}toeta pi^{0}pi^{0}$ is probably caused by the mass difference between charged and neutral pions or radiative corrections. No cusp structure in $eta^{prime}toeta pi^{0}pi^{0}$ is observed.
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Based on a sample of $1.31 times 10^9$ $J/psi$ events collected with the BESIII detector at the BEPCII collider, Dalitz plot analyses of selected 79,625 $etarightarrowpi^{+}pi^{-}pi^0$ events, 33,908 $etarightarrowpi^0pi^0pi^0$ events and 1,888 $eta^{prime}rightarrowpi^0pi^0pi^0$ events are performed. The measured matrix elements of $etarightarrowpi^+pi^-pi^0$ are in reasonable agreement with previous measurements. The Dalitz plot slope parameters of $etarightarrowpi^0pi^0pi^0$ and $eta^{prime}rightarrowpi^0pi^0pi^0$ are determined to be $-0.055 pm 0.014 pm 0.004$ and $-0.640 pm 0.046 pm 0.047$, respectively, where the first uncertainties are statistical and the second systematic. Both values are consistent with previous measurements, while the precision of the latter one is improved by a factor of three. Final state interactions are found to have an important role in those decays.
Based on a sample of $1.31 times 10^9$ $J/psi$ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays $eta^prime rightarrow pi^+pi^-pi^0$ and $eta^prime rightarrow pi^0pi^0pi^0$ is performed. A significant $P$-wave contribution from $eta^prime rightarrow rho^{pm} pi^{mp}$ is observed for the first time in $eta^prime rightarrow pi^+pi^-pi^0$. The branching fraction is determined to be ${mathcal B}(eta^prime rightarrow rho^{pm}pi^{mp})=(7.44pm0.60pm1.26pm1.84)times 10^{-4}$, where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant $S$-wave component, there is a significant $sigma$ meson component. The branching fractions of the combined $S$-wave components are determined to be ${mathcal B}(eta^prime rightarrow pi^+pi^-pi^0)_S=(37.63pm0.77pm2.22pm4.48)times 10^{-4}$ and ${mathcal B}(eta^prime rightarrow pi^0pi^0pi^0)=(35.22pm0.82pm2.54)times 10^{-4}$, respectively. The latter one is consistent with previous BESIII measurements.
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.
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.
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