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Register a new userAmplitude Analysis of the Decays $eta^prime rightarrow pi^+pi^-pi^0$ and $eta^prime rightarrow pi^0pi^0pi^0$
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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.
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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.
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.
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.
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.
A search for $CP$ violation in $D^{pm}rightarrow eta^{prime} pi^{pm}$ and $D^{pm}_{s}rightarrow eta^{prime} pi^{pm}$ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of $3$ fb$^{-1}$, recorded by the LHCb experiment at centre-of-mass energies of $7$ and $8$ TeV. The measured $CP$-violating charge asymmetries are $A_{CP}(D^{pm} rightarrow eta^{prime} pi^{pm})=(-0.61pm 0.72 pm 0.53 pm 0.12)%$ and $A_{CP}(D^{pm}_{s}rightarrow eta^{prime} pi^{pm})=(-0.82pm 0.36 pm 0.22 pm 0.27)%$, where the first uncertainties are statistical, the second systematic, and the third are the uncertainties on the $A_{CP}(D^{pm} rightarrow K^0_S pi^{pm})$ and $A_{CP}(D^{pm}_{s}rightarrow phi pi^{pm})$ measurements used for calibration. The results represent the most precise measurements of these asymmetries to date.
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