相关论文: On the Four--Photon Decay of the Neutral Pion

We provide a new value for the ratio $R={\Gamma(\pi^0\to e^+e^-\gamma(\gamma))}/{\Gamma(\pi^0\to\gamma\gamma)}=11.978(6)\times10^{-3}$, which is by two orders of magnitude more precise than the current Particle Data Group average. It is…

Using a large acceptance calorimeter and a stopped pion beam we have made a precise measurement of the rare Pi+ -> Pi0 e+ Nu,(pi_beta) decay branching ratio. We have evaluated the branching ratio by normalizing the number of observed…

We search for the rare decay of the $D^{0}$ meson to two photons, $D^0 \rightarrow \gamma \gamma$, and present a measurement of the branching fraction for a $D^0$ meson decaying to two neutral pions, ${B}(D^0 \rightarrow \pi^0 \pi^0)$. The…

Using the upper bound on the effective number of light neutrino species during primordial nucleosynthesis and the cosmological pion-pole mechanism $\gamma\gamma\rightarrow \pi^0\rightarrow \gamma X$, we obtain an upper limit on the…

We have performed a measurement of the K^+ -> pi^+ pi^0 gamma decay and have observed 2 X 10^4 events. The best fit to the decay spectrum gives a branching ratio for direct photon emission of (4.7\pm0.8\pm0.3) X 10^{-6} in the pi^+ kinetic…

We present a new determination of the parity of the neutral pion via the double Dalitz decay pi^0 -> e+ e- e+ e-. Our sample, which consists of 30511 candidate decays, was collected from K_L -> pi0 pi0 pi0 decays in flight at the KTeV-E799…

We present a limit on the branching fraction for the decay $B^0 \to \gamma \gamma$ using data collected at the $\Upsilon(4S)$ resonance with the BABAR detector at the PEP-II asymmetric--energy $e^+e^-$ collider. Based on the observation of…

The $K^{+} \to \pi^{+}\pi^{0}\pi^{0}\gamma$ decay is observed by the OKA collaboration. The branching ratio is measured to be $(4.1 \pm 0.9(stat) \pm 0.4(syst))\times 10^{-6}$. The branching ratio and $\gamma$ energy spectrum are consistent…

We report new experimental limits on the \pi^0 -> \gamma X decay of the neutral pion into a photon and a light boson X followed by the decay X -> e+e-. If this process exist, one would expect a flux of high energy X's produced from \pi^0's…

We report a measurement of the branching fractions in the B0->J/Psi pi+pi- decay based on a 140/fb data sample collected at the Upsilon(4S) energy with the Belle detector at the KEKB e+e- collider. Charged pion pairs are found to arise…

We have observed a signal for the decay D*+ -> D+ gamma at a significance of 4 standard deviations. From the measured branching ratio B(D*+ -> D+ gamma)/B(D*+ -> D+ pi0)=0.055 +- 0.014 +- 0.010 we find B(D*+ -> D+ gamma)= 0.017 +- 0.004 +-…

Vector-Meson-Dominance model contribution to $\pi^0 \to 4\gamma$ is calculated. The result confirms old estimates that this contribution is much smaller than the purely electromagnetic photon spliting graph contribution calculated earlier.

By combining a recent estimate of the total B-->X_s gamma branching fraction at O(alpha_s^2) with a detailed analysis of the effects of a cut E_gamma>1.6GeV on photon energy, a prediction for the partial B-->X_s gamma branching fraction at…

The branching ratio of the $K^+\to\pi^+e^+e^-e^+e^-$ ($K^+\to\pi^+4e$) decay is calculated at leading order in the Standard Model. The dominance of the neutral-pion pole determines the overall branching ratio to be…

We have measured the branching ratio BR(phi --> pi0 pi0 gamma) with the KLOE detector using a sample of ~5x10^7 phi decays. phi mesons are produced at DAFNE, the Frascati phi-factory. We find BR(phi --> pi0 pi0 gamma) = (1.09 +- 0.03 (stat)…

Rare radiative decay $\phi\to\eta\pi^0\gamma$ was studied with SND detector at {VEPP-2M} electron-positron collider and its branching ratio was measured: $B(\phi\to\eta\pi^0\gamma)=(0.88\pm0.14\pm0.09)\cdot 10^{-4}$. Significant…

Using 11.6 1/pb of data collected in the energy range 0.864-1.06 GeV by CMD-2 at VEPP-2M, the rare decay mode phi to eta' gamma was observed via the decay chain eta' to pi+pi- eta, eta to pi+pi-pi0 or eta to pi+pi- gamma. The following…

In the SND experiment at the VEPP-2M electron-positron collider the PHI(1020)--->PI0+PI0+GAMMA decay was studied. The branching ratio B(PHI--->PI0+PI0+GAMMA)=(1.14+-0.10+-0.12)x10^{-4} was measured. It was shown, that the F0(980)GAMMA…

Using 482 pb$^{-1}$ of data taken at $\sqrt{s}=4.009$ GeV, we measure the branching fractions of the decays of $D^{*0}$ into $D^0\pi^0$ and $D^0\gamma$ to be $\BR(D^{*0} \to D^0\pi^0)=(65.5\pm 0.8\pm 0.5)%$ and $\BR(D^{*0} \to…

The experimental branching ratio for the radiative decay $\rho^{0}\to\pi^{+}+\pi^{-}+\gamma$ is used to estimate the coupling constant $g_{\rho\sigma\gamma}$ for a set of values of $\sigma$-meson parameters M$_{\sigma}$ and…