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Register a new userA partial wave analysis of the $pi ^0pi ^0$ system produced in $pi ^-p$ charge exchange collisions
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A partial wave analysis of the of the $pi ^0pi ^0$ system produced in the charge exchange reaction: $pi ^-pto pi ^0pi ^0n$ at an incident momentum of $18.3 GeV/c$ is presented as a function of ${pi ^0pi ^0}$ invariant mass, $m_{pi^0pi^0}$, and momentum transfer squared, $| {t} |$, from the incident $pi^-$ to the outgoing ${pi ^0pi ^0}$ system.
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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.
A partial wave analysis (PWA) of the $pi^- pi^- pi^+$ and $pi^- pi^0 pi^0$ systems produced in the reaction $pi^- p to (3pi)^-p$ at 18 GeV/$c$ was carried out using an emph{isobar} model assumption. This analysis is based on 3.0M $pi^- pi^0 pi^0$ events and 2.6M $pi^- pi^-pi^+$ events and shows production of the $a_1(1260)$, $a_2(1320)$, $pi_2(1670)$ and $a_4(2040)$ resonances. Results of detailed studies of the stability of partial wave fits are presented. An earlier analysis of 250K $pi^- pi^- pi^+$ events from the same experiment showed possible evidence for a $J^{PC}=1^{-+}$ exotic meson with a mass of $sim$1.6 GeV/$c^2$ decaying into $rho pi$. In this analysis of a higher statistics sample of the $(3pi)^-$ system in two charged modes we find no evidence of an exotic meson.
An amplitude analysis of the $pi^{0}pi^{0}$ system produced in radiative $J/psi$ decays is presented. In particular, a piecewise function that describes the dynamics of the $pi^{0}pi^{0}$ system is determined as a function of $M_{pi^{0}pi^{0}}$ from an analysis of the $(1.311pm0.011)times10^{9}$ $J/psi$ decays collected by the BESIII detector. The goal of this analysis is to provide a description of the scalar and tensor components of the $pi^0pi^0$ system while making minimal assumptions about the properties or number of poles in the amplitude. Such a model-independent description allows one to integrate these results with other related results from complementary reactions in the development of phenomenological models, which can then be used to directly fit experimental data to obtain parameters of interest. The branching fraction of $J/psi to gamma pi^{0}pi^{0}$ is determined to be $(1.15pm0.05)times10^{-3}$, where the uncertainty is systematic only and the statistical uncertainty is negligible.
A partial-wave analysis of the decay $J/psi to K^+K^-pi^0$ has been made using $(223.7pm1.4)times 10^{6}$ $J/psi$ events collected with the BESIII detector in 2009. The analysis, which is performed within the isobar-model approach, reveals contributions from $K^*_2(1430)^pm$, $K^*_2(1980)^pm$ and $K^*_4(2045)^pm$ decaying to $K^pmpi^0$. The two latter states are observed in $J/psi$ decays for the first time. Two resonance signals decaying to $K^+K^-$ are also observed. These contributions can not be reliably identified and their possible interpretations are discussed. The measured branching fraction $B(J/psi to K^+K^-pi^0)$ of $(2.88pm0.01pm0.12)times10^{-3}$ is more precise than previous results. Branching fractions for the reported contributions are presented as well. The results of the partial-wave analysis differ significantly from those previously obtained by BESII and BABAR.
We present a measurement of $B(pi^0 rightarrow e^+e^- gamma)/B(pi^0 rightarrow gammagamma)$, the Dalitz branching ratio, using data taken in 1999 by the E832 KTeV experiment at Fermi National Accelerator Laboratory. We use neutral pions from fully reconstructed $K_L$ decays in flight; the measurement is based on about 60 thousand $K_L rightarrow pi^0pi^0pi^0 rightarrow gammagamma~gammagamma~e^+e^-gamma$ decays. We normalize to $K_L rightarrow pi^0pi^0pi^0 rightarrow 6gamma$ decays. We find $B(pi^0 rightarrow e^+e^- gamma)/B(pi^0 rightarrow gammagamma)$ $(m_{e^+e^-}$ > 15 MeV/$c^2)$ = $[3.920 pm 0.016(stat) pm 0.036 (syst)] times 10^{-3}$. Using the Mikaelian and Smith prediction for the $e^+e^-$ mass spectrum, we correct the result to the full $e^+e^-$ mass range. The corrected result is $B(pi^0 rightarrow e^+e^- gamma)/B(pi^0 rightarrow gammagamma) = [1.1559 pm 0.0047(stat) pm 0.0106 (syst)]$%. This result is consistent with previous measurements and the uncertainty is a factor of three smaller than any previous measurement.
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