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Register a new userSearch for the rare decay $etarightarrowpi^{0}pi^{0}pi^{0}pi^{0}$ at BESIII
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Based on a sample of 1.31 billion $J/psi$ events collected with the BESIII detector, we perform a search for the rare decay $etarightarrow 4pi^{0}$ via $J/psirightarrowgammaeta$. No significant $eta$ signal is observed in the invariant mass spectrum of 4$pi^{0}$. With a Bayesian approach, the upper limit on the branching fraction of $etarightarrow 4pi^{0}$ is determined to be $mathcal{B}(etarightarrow 4pi^{0})$ $< 4.94times10^{-5}$ at the 90% confidence level, which is a factor of six smaller than the previous experimental limit.
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The KTeV E799 experiment has conducted a search for the rare decay $K_{L}topi^{0}pi^{0}gamma$ via the topology $K_{L}topi^{0}pi^{0}_Dgamma$ (where $pi^0_Dtogamma e^+e^-$). Due to Bose statistics of the $pi^0$ pair and the real nature of the photon, the $K_{L}topi^{0}pi^{0}gamma$ decay is restricted to proceed at lowest order by the CP conserving direct emission (DE) of an E2 electric quadrupole photon. The rate of this decay is interesting theoretically since chiral perturbation theory predicts that this process vanishes at level $O(p^4)$. Therefore, this mode probes chiral perturbation theory at $O(p^6)$. In this paper we report a determination of an upper limit of $2.43times 10^{-7}$ (90% CL) for $K_{L}topi^{0}pi^{0}gamma$. This is approximately a factor of 20 lower than previous results.
We search for CP violation in neutral charm meson decays using a data sample with an integrated luminosity of 966 fb^-1 collected with the Belle detector at the KEKB e+e- asymmetric-energy collider. The asymmetry obtained in the rate of D^0 and D^0-bar decays to the pi^0 pi^0 final state, [-0.03+-0.64(stat)+-0.10(syst)]%, is consistent with no CP violation. This constitutes an order of magnitude improvement over the existing result. We also present an updated measurement of the CP asymmetry in the D^0 -> K_S pi^0 decay: A_{CP}(D^0 -> K_S pi^0) = [-0.21+-0.16(stat)+-0.07(syst)]%.
Using a data sample of $e^+e^-$ collision data corresponding to an integrated luminosity of 2.93 $fb^{-1}$ collected with the BESIII detector at a center-of-mass energy of $sqrt{s}= 3.773~GeV$,we search for the singly Cabibbo-suppressed decays $D^{0}topi^{0}pi^{0}pi^{0}$, $pi^{0}pi^{0}eta$, $pi^{0}etaeta$ and $etaetaeta$ using the double tag method. The absolute branching fractions are measured to be $mathcal{B}(D^{0}topi^{0}pi^{0}pi^{0}) = (2.0 pm 0.4 pm 0.3)times 10^{-4}$, $mathcal{B}(D^{0}topi^{0}pi^{0}eta) = (3.8 pm 1.1 pm 0.7)times 10^{-4}$ and $mathcal{B}(D^{0}topi^{0}etaeta) = (7.3 pm 1.6 pm 1.5)times 10^{-4}$ with the statistical significances of $4.8sigma$, $3.8sigma$ and $5.5sigma$, respectively, where the first uncertainties are statistical and the second ones systematic. No significant signal of $D^{0}toetaetaeta$ is found, and the upper limit on its decay branching fraction is set to be $mathcal{B}(D^{0}toetaetaeta) < 1.3 times 10^{-4}$ at the $90%$ confidence level.
We present the results of a Dalitz plot analysis of D^0 to K^0_S pi^0 pi^0 using the CLEO-c data set of 818 inverse pico-barns of e^+ e^- collisions accumulated at sqrt{s} = 3.77 GeV. This corresponds to three million D^0 D^0-bar pairs from which we select 1,259 tagged candidates with a background of 7.5 +- 0.9 percent. Several models have been explored, all of which include the K^*(892), K^*_2(1430), K^*(1680), the f_0(980), and the sigma(500). We find that the combined pi^0 pi^0 S-wave contribution to our preferred fit is (28.9 +- 6.3 +- 3.1)% of the total decay rate while D^0 to K^*(892)^0 pi^0 contributes (65.6 +- 5.3 +- 2.5)%. Using three tag modes and correcting for quantum correlations we measure the D^0 to K^0_S pi^0 pi^0 branching fraction to be (1.059 +- 0.038 +- 0.061)%.
Proton-proton collision data recorded in 2011 and 2012 by the lhcb experiment, co-rres-pon-ding to an integrated luminosity of 3.0invfb, are a-na-lysed to search for the charmless ${B^0 to rho^0 rho^0}$ decay. More than 600 ${B^0 to (pi^+pi^-)(pi^+pi^-)}$ signal decays are selected and used to perform an amplitude analysis from which the ${B^0 to rho^0 rho^0}$ decay is observed for the first time with 7.1 standard deviations significance. The fraction of ${B^0 to rho^0 rho^0}$ decays yielding a longitudinally polarised final state is measured to be $fL = 0.745^{+0.048}_{-0.058} ({rm stat}) pm 0.034 ({rm syst})$. The ${B^0 to rho^0 rho^0}$ branching fraction, using the ${B^0 to phi K^*(892)^{0}}$ decay as reference, is also reported as ${BF(B^0 to rho^0 rho^0) = (0.94 pm 0.17 ({rm stat}) pm 0.09 ({rm syst}) pm 0.06 ({rm BF})) times 10^{-6}}$.
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