Related papers: First Observation of the Rare Decay Mode K-long ->…
Using 14M psi(2S) events taken with the BES-II detector, chi_cJ-->K+K-K+K- decays are studied. For the four-kaon final state, the branching fractions are B(chi_c0,1,2 -->K+K-K+K-)=(3.48\pm 0.23\pm 0.47)\times 10^{-3}, (0.70\pm 0.13\pm…
We report the first observation of the exclusive decay process B->J/psi K1(1270) using a sample of 11.2M BBbar meson pairs collected in the Belle detector at the KEKB asymmetric e+e- collider. We measure branching fractions of Bf(B0 ->…
Within the dispersive approach to the amplitude of the rare decay pi0 -> e+e- the nontrivial dynamics is contained only in the subtraction constant. We express this constant, in the leading order in (m_e/\Lambda)^2 perturbative series, in…
We report on a new measurement of the branching ratio B(KL -> pi0 e+ e- gamma) using the KTeV detector. This analysis uses the full KTeV data set collected from 1997 to 2000. We reconstruct 139 events over a background of 14, which results…
The NA62 experiment reports an investigation of the $K^+\rightarrow\pi^+\nu\bar{\nu}$ mode from a sample of $K^+$ decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of $(0.389\pm…
An event consistent with the signature expected for the rare kaon decay K+ --> pi+ nu anti-nu has been observed. In the pion momentum region examined, 211<P<230 MeV/c, the backgrounds are estimated to contribute 0.08 +/- 0.03 events. If the…
We present evidence for the flavor-changing neutral current decay $B\to K^*\ell^+\ell^-$ and a measurement of the branching fraction for the related process $B\to K\ell^+\ell^-$, where $\ell^+\ell^-$ is either an $e^+e^-$ or $\mu^+\mu^-$…
We present a measurement of the branching fractions of four $B^{0,-}\to D^{(*)+,0} K^- K^{0}_S$ decay modes. The measurement is based on data from SuperKEKB electron-positron collisions at the $\Upsilon(4S)$ resonance collected with the…
In a sample of 6.6 million produced B mesons we have observed decays B -> eta' K, with branching fractions BR(B+ -> eta' K+ = 6.5 +1.5 -1.4 +- 0.9) x $10^{-5}$ and BR(B0 -> eta' K0 = 4.7 +2.7 -2.0 +- 0.9) x $10^{-5}$. We have searched with…
We present a measurement of the branching fraction of the decay B0 --> a1(1260)^{+-} pi^{-+} with a1(1260)^{+-} --> pi^{-+} pi^{+-} pi^{+-}. The data sample consists of 218 million B B-bar pairs collected at the Y(4S) resonance and recorded…
We report the first measurement of the absolute branching fraction e^+e^- --> B0B0bar at the Upsilon(4S) resonance using data collected with the BABAR detector at the PEP-II asymmetric-energy e^+e^- storage ring. The analysis is performed…
We present measurements of the flavor-changing neutral current decays B --> Kl+l- and B --> K*l+l-, where l+l- is either an e+e- or mu+mu- pair. The data sample comprises 229 x 10^6 Y(4s) -->to BBbar decays collected with the BaBar detector…
We report the first observation of radiative decay B^0 -> \phi K^0 \gamma using a data sample of 772x10^6 BBar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We observe a signal…
We report an observation of the decay B^\pm -> \phi \phi K^\pm and evidence for B^0 -> \phi \phi K^0. These results are based on a 414 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy e^+e^- collider…
A search for the decay K_S -> pi^0mu^+mu^- has been made by the NA48/1 Collaboration at the CERN SPS accelerator. The data were collected during 2002 with a high-intensity K_S beam. Six events were found with a background expectation of…
Using data collected with the babar detector between 1999 and 2002, we report the observation of 823+-57 B0 and 969+-65 B+ decays to Dbar(*)D^(*)K, where Dbar(*) and D(*) are fully reconstructed and where K is either a K+ or a K0_S decaying…
We report on a search for the decay Kl -> pi0 e+ e- carried out by the KTeV/E799 experiment at Fermilab. This decay is expected to have a significant CP violating contribution and the measurement of its branching ratio could support the CKM…
Using 449 million BBbar pairs collected with the Belle detector at the KEKB asymmetric-energy e^+e^- collider, we observe clear signals for B^+-> \bar{K}^0 K^+ and B^0-> \bar{K}^0 K^0 decays with 5.3 sigma and 6.0 sigma significance,…
We present the first measurements of branching fractions of rare tau-lepton decays, $\tau^- \rightarrow \pi^- \nu_{\tau} \ell^+ \ell^-$ ($\ell = e$ or $\mu$), using a data sample corresponding to 562 fb$^{-1}$ collected at a center-of-mass…
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…