The decays $J/psi rightarrow gamma pi^+pi^-pi^0$ and $J/psi rightarrow gamma pi^0pi^0pi^0$ are analyzed using a sample of 225 million $jpsi$ events collected with the BESIII detector. The decay of $eta(1405)ar f_{0}(980)pi^0$ with a large isospin violation is observed for the first time. The width of the $f_{0}(980)$ observed in the dipion mass spectra is anomalously narrower than the world average. Decay rates for three-pion decays of the $eta$ are also measured precisely.
We report the first observation of $a^{0}_{0}(980)$-$f_{0}(980)$ mixing in the decays of $J/psitophi f_{0}(980)tophi a^{0}_{0}(980)tophietapi^{0}$ and $chi_{c1}to a^{0}_{0}(980)pi^{0}to f_{0}(980)pi^{0}topi^{+}pi^{-}pi^{0}$, using data samples of $1.31times10^{9}$ $J/psi$ events and $4.48times10^{8}$ $psi(3686)$ events accumulated with the BESIII detector. The signals of $f_{0}(980)to a^{0}_{0}(980)$ and $a^{0}_{0}(980)to f_{0}(980)$ mixing are observed at levels of statistical significance of $7.4sigma$ and $5.5sigma$, respectively. The corresponding branching fractions and mixing intensities are measured and the constraint regions on the coupling constants, $g_{a_{0}K^{+}K^{-}}$ and $g_{f_{0}K^{+}K^{-}}$, are estimated. The results improve the understanding of the nature of $a^{0}_{0}(980)$ and $f_{0}(980)$.
We present the first amplitude analysis of the decay $D^{+}_{s} rightarrow pi^{+}pi^{0}eta$. We use an $e^{+}e^{-}$ collision data sample corresponding to an integrated luminosity of 3.19~${mbox{,fb}^{-1}}$ collected with the BESIII detector at a center-of-mass energy of $4.178$ GeV. We observe for the first time the pure $W$-annihilation decays $D_{s}^{+} rightarrow a_{0}(980)^{+}pi^{0}$ and $D_{s}^{+} rightarrow a_{0}(980)^{0}pi^{+}$. We measure the absolute branching fractions $mathcal{B}(D_{s}^{+} rightarrow a_{0}(980)^{+(0)}pi^{0^(+)}, a_{0}(980)^{+(0)} to pi^{+(0)}eta) = (1.46pm0.15_{{rm stat.}}pm0.23_{{rm sys.}})$%, which is larger than the branching fractions of other measured pure $W$-annihilation decays by at least one order of magnitude. In addition, we measure the branching fraction of $D_{s}^{+} rightarrow pi^{+}pi^{0}eta$ with significantly improved precision.
Using 9.0/fb of integrated luminosity in e+e- collisions near Upsilon(4S) mass collected with the CLEO II.V detector we report the first observation of the decay D0 -> K0S ETA PI0 We measure the ratio of branching fractions, BR(D0 -> K0S ETA PI0) / BR(D0 -> K0S PI0) = 0.46 +- 0.07 +- 0.06. We perform a Dalitz analysis of 155 selected D0 -> K0S ETA PI0 candidates and find leading contributions from a_0(980) K0S and K*(892) ETA intermediate states.
We report a measurement of differential cross section of $pi^{0}$ pair production in single-tag two-photon collisions. These results are obtained with 759$fb^{-1}$ of the data collected with the Belle detector at the KEKB asymmetric energy $e^{+}e^{-}$ collider. The cross section is measured for $Q^{2}$ up to 30 GeV$^{2}$, where $Q^{2}$ is the negative of the invariant mass squared of the tagged virtual photon, in the kinematic range 0.5 GeV < $W$ < 2.1 GeV and |cos$theta^{*}$| < 1.0 for the total energy and pion scattering angle, respectively. The transition form factor of the $f_{0}(980)$ and that of the $f_{2}(1270)$ with the helicity-0,-1, and -2 components separately are measured for the first time and are compared with theoretical calculations.
Using a sample of 1.31 billion $J/psi$ events collected with the BESIII detector at the BEPCII collider, the decays $J/psi to phi pi^{+}pi^{-}pi^{0}$ and $J/psi to phi pi^{0}pi^{0}pi^{0}$ are investigated. The isospin violating decay $J/psi to phi pi^{0} f_{0}(980)$ with $f_{0}(980) to pipi$, is observed for the first time. The width of the $f_{0}(980)$ obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the $pi^{0} f_{0}(980)$ mass spectrum, there is evidence of $f_1(1285)$ production. By studying the decay $J/psi to phieta$, the branching fractions of $eta to pi^{+}pi^{-}pi^{0}$ and $eta to pi^{0}pi^{0}pi^{0}$, as well as their ratio, are also measured.