Related papers: Rare K+ Decays from Experiment E787

A sample of 400000 events from the decay K+->pi+pi-e+nu(e)(K(e4)) has been collected in experiment E865 at the Brookhaven AGS. The analysis of these data yields new measurements of the K(e4) branching ratio (4.11+-0.01+-0.11)*10**(-5)), the…

Experiment E865 at the Brookhaven AGS was set up primarily to search for the lepton flavour violating decay $K^+\to \pi^+\mu^+e^-$ ($K_{\pi\mu e}$) with high sensitivity. The flexibility of the apparatus allowed also to obtain more than an…

I present some of the most recent BaBar measurements for rare B decays. These include rate asymmetries in the B decays to K(*) l+ l- and K+ pi- and branching fractions in the B decays to l+ nu_l, K_1(1270)+ pi- and K_1(1400)+ pi-. I also…

A brief review of current results on rare kaon decays, particularly the charged and neutral K-> pi nu nubar channels, is presented along with prospects for future measurements.

Using data collected with the HyperCP (E871) spectrometer during the 1997 fixed-target run at Fermilab, we report the first observation of the decay K- -> pi- mu+ mu- and new measurements of the branching ratios for K+/- -> pi+/- mu+ mu- .…

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…

Simple dynamics, few available decay channels, and highly controlled radiative and loop corrections, make pion and muon decays a sensitive means of exploring details of the underlying symmetries. We review the current status of the rare…

After a decade of no measurements of pion and muon rare decays, PIBETA, a new experimental program is producing its first results. We report on a new experimental study of the pion beta decay, Pi(+) -> Pi(0) e(+) Nu, the Pi(e2 gamma)…

The first search for ultra-rare $K^+$ decays into the $\pi^+e^+e^-e^+e^-$ final state is reported, using a dataset collected by the NA62 experiment at CERN in 2017-2018. An upper limit of $1.4\times 10^{-8}$ at 90% CL is obtained for the…

We present a concise review of the theoretical status of rare K -> pi nu nubar decays in the standard model (SM). Particular attention is thereby devoted to the recent calculation of the next-to-next-to-leading order (NNLO) corrections to…

The NA62 experiment, proposed to measure the very rare decay K+ to pi+ nu nubar at the CERN SPS with 10% accuracy, aims to collect about 80 events in two years of data taking, keeping background contamination lower than 10%. This paper…

The experimental program for the study of the rare kaon decays, K -> pnn, is summarized. A review of recent results is provided along with a discussion of prospects for the future of this program. The primary focus of the world-wide kaon…

Rare decays of K mesons are reviewed from the perspective of testing the ``ones'' and ``zeros'' of the standard model. Decays K^+ -> pi^+ nu anti-nu and K_L -> pi^0 nu anti-nu probe the one-loop effective Hamiltonian for s -> d nu anti-nu,…

Rare kaon decays provide unique opportunity to test the Standard Model and probe its possible extensions. The final result on the lepton universality test by measuring the ratio R_K = G(K+- to e+- nu)/G(K+- to mu+- nu) is presented as well…

We report experimental details and results of a new measurement of the decay K+ -> pi+pi-e+nue (Ke4}. A sample of more than 400,000 Ke4 events with low background has been collected by Experiment 865 at the Brookhaven Alternate Gradient…

We review the recent measurements of the rare pion decays: Pi+ -> Pi0 e+ Nu [pion beta, Pi_(e3), or Pi_beta decay], radiative decay Pi+ -> e+ Nu Gamma [Pi_(e2Gamma) or RPD], and Pi+ -> e+ Nu [Pi_(e2)] decay, as well as the radiative muon…

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…

Soon the NA62 experiment will start looking for the rare K+ ---> pi+ nu nu bar decay. In this talk, its theoretical interests, together with those of the neutral rare decays KL ---> pi0 nu nu bar, KL ---> pi0 e+ e-, and KL ---> pi0 mu+ mu-,…

More than 400 $K^{+}\to\pi^{+}\mu^+\mu^-$ events were observed in a rare $K^+$ decay experiment at the AGS. Normalized to the $K^{+}\to\pi^{+}\pi^+\pi^-$ decay, the branching ratio is determined to be $(9.22 \pm 0.60 (stat) \pm 0.49…

We report a search for the rare decays B -> h(*) nu nubar, where h(*) stands for K+, Ks0, K*+, K*0, pi+, pi0, rho+, rho0 and phi. The results are obtained from a 711 fb-1 data sample that contains 772 million BB pairs collected at the Y(4S)…