相关论文: Results from the NA62 2014 Commissioning Run
In an experiment designed to search for and study very rare two-body decay modes of the K-long, we have observed four examples of the decay K-long -> e+ e-, where the expected background is 0.17+-0.10 events. This observation translates…
We have observed 1 event consistent with the signature expected of the rare decay of a positive kaon to a positive pion and a neutrino anti-neutrino pair. In the examined momentum region of 211 to 230 MeV/c in the center of mass of the kaon…
Precise measurements of the branching ratios for the flavor-changing neutral current decays $K\to\pi\nu\bar{\nu}$ can provide unique constraints on CKM unitarity and, potentially, evidence for new physics. It is important to measure both…
The rare decay $\eta' \to \pi^+ \pi^- e^+ e^-$ is studied using a sample of $1.3 \times 10^9$ $J/\psi$ events collected with the BESIII detector at BEPCII in 2009 and 2012. The branching fraction is measured with improved precision to be…
We report a new measurement of the decay \Omega^- \to \Xi^- \pi^+ \pi^- with 76 events and a first observation of the decay \Omega^+ \to \Xi^+ \pi^+ \pi^- with 24 events, yielding a combined branching ratio (3.74 ^{+0.67}_{-0.56}) \times…
We compute the branching ratios for the radiative rare decays of B into K-Meson states and compare them to the experimentally determined branching ratio for inclusive decay b -> s gamma using non relativistic quark model, and form factor…
We have observed the rare decay K+ --> pi+ mu+ mu- and measured the branching ratio Gamma(K+ --> pi+ mu+ mu-)/Gamma(K+ --> all) = (5.0 +/- 0.4 (stat.) +/- 0.7 (sys.) +/- 0.6 (theor.)) x 10^{-8}. We compare this result with predictions from…
We have analyzed 1.62 fb$^{-1}$ of $e^{+}e^{-}$ collisions at a center of mass energy $\sim M_{\phi}$ collected by the KLOE experiment at DA$\Phi$NE. This sample corresponds to a production of $\sim$ 1.7 billion of $\ks$ $\kl$ pairs which…
Measurement of the branching ratios for $6P_{1/2}$ decays to $6S_{1/2}$ and $5D_{3/2}$ in $^{138}$Ba$^+$ are reported with the decay probability from $6P_{1/2}$ to $5D_{3/2}$ measured to be…
We measure the branching fractions for the decays $\bar{B}^0 \to D^{*+} e^{-} \bar{\nu}_e$ and $\bar{B}^0 \to D^{*+} \mu^{-} \bar{\nu}_\mu$ using $8.70 \pm 0.09~{\rm fb}^{-1}$ of data collected by the Belle II experiment at the SuperKEKB…
New results of a search for the ultra-rare decay $\mu \to e \gamma$ by the MEG collaboration are reported in this contribution. The data were taken during 2009 and correspond to approximately 6.5 10$^{13}$ muon stopped on target. A maximum…
Experiment 865 at the Brookhaven AGS has observed the decay K^+ -> e^+ nu mu^+ mu^-. The branching ratio extracted is (1.72 +/- 0.37(stat) +/- 0.17(syst) +/- 0.19(model)) x 10^{-8} where the third term in the error results from the use of a…
From a sample of 232 million Upsilon(4S)--> B B-bar events collected with the BABAR detector at the PEP-II B Factory in 1999--2004, we measure the B- --> D0 K*-(892) decay branching fraction using events where the K*- is reconstructed in…
Using 65 million $\Upsilon(4S)\to B\bar{B}$ events collected with the BABAR detector at the PEP-II $e^{+}e^{-}$ storage ring at the Stanford Linear Accelerator Center, we measure the color-favored branching fractions ${\cal B}(\bar{B^{0}}…
The NA62 experiment collected a large sample of charged kaon decays in 2007 with a highly efficient trigger for decays into electrons. A measurement of the $\pi^0$ electromagnetic transition form factor slope parameter from…
The decay $K_L \to \gamma \nu \bar{\nu}$ is analyzed within the standard model. Short-distance contributions are found to dominate, yielding a branching ratio of $\sim 0.7 \times 10^{-11}$. We examine the possibility that non-standard model…
Three events for the decay K+ => pi+,nu,nubar have been observed in the pion momentum region below the K+ => pi+,pi0 peak, 140 < P_pi < 199 MeV/c, with an estimated background of 0.93+-0.17(stat.)+0.32-0.24(syst.) events. Combining this…
We present preliminary measurements of branching fractions for the charmless two-body decays B0 -> pi+pi- and K+pi-, and a search for B0 -> K+K- using a data sample of approximately 227 million BBbar decays. Signal yields are extracted with…
We present a new measurement of the branching ratio for the decay of $^{14}$O to the ground state of $^{14}$N. The experimental result, $\lambda _0/\lambda _{\rm total} = (4.934 \pm 0.040\kern 1pt{\rm (stat.)} \pm 0.061\kern 1pt{\rm…
The half-life, 3.8755(12) s, and superallowed branching ratio, 0.5315(12), for ^{22}Mg beta-decay have been measured with high precision. The latter depended on gamma-ray intensities being measured with an HPGe detector calibrated for…