Related papers: Experimental search for the decay mode K_L -> pi^0…

The first search for the rare kaon decay $\kppnn$ has been performed by the E391a collaboration at the KEK 12-GeV proton synchrotron. An upper limit of $4.7\times10^{-5}$ at the 90 % confidence level was set for the branching ratio of the…

The OKA Collaboration has obtained a new upper limit on the $K^+ \to \pi^0\pi^0\pi^0 e^+ \nu$ decay probability which is 65 times lower than the one currently listed by PDG. However it is still about $10^{4}$ times worse than the…

We report on a study of the decay $K_L \to e^+e^-\gamma\gamma$ carried out as a part of the KTeV/E799 experiment at Fermilab. The 1997 data yielded a sample of 1543 events, including an expected background of $56 \pm 8$ events. An effective…

We searched for the $CP$-violating rare decay of neutral kaon, $K_{L} \to \pi^0 \nu \overline{\nu}$, in data from the first 100 hours of physics running in 2013 of the J-PARC KOTO experiment. One candidate event was observed while…

We present a new result on the K^+ --> pi^+ pi^0 gamma decay measurement using stopped kaons. The best fit to the decay spectrum comprised of 10k events gives a branching ratio for the direct photon emission of [3.8+-0.8(stat)+-0.7(syst)]…

We report the observation of the radiative decay B+ --> K1(1270)+ gamma using a data sample of 140 fb-1 taken at the Upsilon(4S) resonance with the Belle detector at the KEKB e+e- collider. We find the branching fraction to be Br(B+ -->…

We have measured the absolute branching ratio of the K+ -> pi+ pi0 (gamma) decay, using about 20 million tagged K+ mesons collected with the KLOE detector at DAFNE, the Frascati phi-factory. Signal counts are obtained from the fit of the…

We performed a search for a light pseudoscalar particle $X$ in the decay $K_L^0->pi0pi0X$, $X->\gamma\gamma$ with the E391a detector at KEK. Such a particle with a mass of 214.3 MeV/$c^2$ was suggested by the HyperCP experiment. We found no…

We report the observation of the radiative decay B+ --> K1(1270)+ gamma using a data sample of 140 fb-1 taken at the Upsilon(4S) resonance with the Belle detector at the KEKB e+e- collider. We find the branching fraction to be Br(B+ -->…

We report the results of the first search for the decay $B_s^0 \to \eta^\prime K_S^0$ using $121.4\,{\rm fb}^{-1}$ of data collected at the $\Upsilon(5S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider.…

Data from the KTeV experiment have provided many opportunities for studies of fundamental symmetries in nature, not just CP. We present new limits on the lepton flavor violating decays K_L -> pi0 mu e, K_L -> pi0 pi0 mu e and pi0 -> mu e.…

The radiative decay $B \to \phi K \gamma$ is observed for the first time. The branching fraction for the charged $B^- \to \phi K^- \gamma$ decay mode is measured to be ${\cal B}(B^- \to \phi K^- \gamma) = (3.4 \pm 0.9 \pm 0.4) \times…

The most sensitive experiment to date to search for the muon and electron lepton number violating decay $K^0_L \to \mu^\pm e^\mp$ has detected no events consistent with this process. Based on this result, the 90% confidence level upper…

The first observation of the decay K^+ --> pi^+ gamma gamma is reported. A total of 31 events was observed with an estimated background of 5.1 +- 3.3 events in the pi+ momentum range from 100 MeV/c to 180 MeV/c. The corresponding partial…

We report a search for the decays $B^0\to K^{*0} \overline{K}{}^{*0}$ and $B^0\to K^{*0} K^{*0}$. We also measure other charmless decay modes with $K^+\pi^-K^-\pi^+$ and $K^{+}\pi^{-}K^{+}\pi^{-}$ final states. The results are obtained from…

This presentation reports on the first experimental search for the decay Klong to $\pi^0 \pi^0 \mu^+ \mu^-$ based on data collected by the KTeV experiment. Although this decay mode is possible within the standard model, its rate is phase…

We present a measurement of the ratio of the decay rates Gamma(KL -> pi+ pi-)/Gamma(KL -> pi e nu), denoted as Gamma(K2pi)/Gamma(Ke3). The analysis is based on data taken during a dedicated run in 1999 by the NA48 experiment at the CERN…

We report on a search for the decay \klpimumu carried out as a part of the KTeV experiment at Fermilab. This decay is expected to have a significant $CP$ violating contribution and a direct measurement will either support the CKM mechanism…

We have searched for the lepton-flavor-violating decay tau -> e gamma using a data sample of 86.7/fb collected with the Belle detector at the KEKB asymmetric e^+ e^- collider. No evidence for a signal is obtained, and we set an upper limit…

We analyze the decay $K_L \to \pi^0 \nu \bar \nu$ in a model independent way. If lepton flavor is conserved the final state is (to a good approximation) purely CP even. In that case this decay mode goes mainly through CP violating…