Related papers: Measurement of the K_L -> e+ e- e+ e- Decay Rate
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…
Direct CP violation is studied in two pion decays of the neutral kaon. Using data collected in the first beam period in 1997, the result for the parameter Re(epsilon'/epsilon) is (18.5+/-4.5(stat)+/-5.8(syst))x10^(-4).
The direct CP violation parameter Re(epsilon'/epsilon) has been measured from the decay rates of neutral kaons into two pions using the NA48 detector at the CERN SPS. With 3.3 million KL->pi0pi0 events collected during the 1998 and 1999…
We studied the radiative muon decay $\mu^+ \to e^+\nu\bar{\nu}\gamma$ by using for the first time an almost fully polarized muon source. We identified a large sample (~13000) of these decays in a total sample of 1.8x10^14 positive muon…
The rare kaon decay program at BNL is summarized. A brief review of recent results is provided along with a discussion of prospects for the future of this program. The primary focus is the two golden modes: k+->pnn and kl->pnn. The first…
New measurements of the $\eta$ and $K^0$ masses have been performed using decays to 3$\pi^0$ with the NA48 detector at the CERN SPS. Using symmetric decays to reduce systematic effects, the results $M(\eta) = 547.843\pm0.051$ MeV/c$^2$ and…
Precision measurements of the branching ratios (BRs) for rare kaon decays can provide unique constraints on CKM unitarity and may reveal the existence of new physics. The BRs for two of these decays, $K^+\to\pi^+\nu\bar{\nu}$ and…
The NA62 experiment at CERN aims to make a precision measurement of the ultra-rare decay $K^{+} \rightarrow \pi^{+}\nu\overline{\nu}$, and relies on a differential Cherenkov detector (KTAG) to identify charged kaons at an average rate of 50…
The NA62 experiment at CERN SPS aims to measure the Branching Ratio of the very rare kaon decay K+ -> pi+ nu nubar collecting O(100) events with a 10% background to make a stringent test of the Standard Model. One of the main backgrounds to…
The NA62 experiment at CERN SPS aims to measure the Branching Ratio of the very rare kaon decay K+ -> pi+ nu nubar collecting O(100) events with a 10% background to make a stringent test of the Standard Model. One of the main backgrounds to…
We report measurements of radiative B decays with K eta gamma final states, using a data sample of 253 /fb recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB e+e- storage ring. We observe B+ -> K+ eta gamma for the…
One-prong tau decays into final states involving kaons are studied with about 161k tau+tau- events collected by the ALEPH detector from 1991 to 1995. Charged kaons are identified by dE/dx measurement, while K0L's are detected through their…
Additional evidence for the rare kaon decay K+ to pi+ neutrino-antineutrino has been found in a new data set with comparable sensitivity to the previously reported result. One new event was observed in the pion momentum region examined,…
In the first year of physics run, the E949 experiment at Brookhaven National Laboratory has already collected $1.8\times 10^{12}$ kaons stopping in the target. Additional evidence for the rare charged kaon decay $K^+\to\pi^+\nu\bar{\nu}$…
A sample of 3984 candidates of the $K^+\to\pi^+\gamma\gamma$ decay, with an estimated background of $291\pm14$ events, was collected by the NA62 experiment at CERN during 2017-2018. In order to describe the observed di-photon mass spectrum,…
We have measured the ratio R=Gamma(Ks -> pi+pi-gamma)/Gamma(Ks -> pi0pi0) with the KLOE detector at the DAFNE e+e- collider. This measurement is fully inclusive with respect to the pi+pi-gamma final state. The sample of over 10^6 two-pion…
We present measurements of B-meson decays to the final states eta'rho, eta'f0, and eta'K*, where K* stands for a vector, scalar, or tensor strange meson. We observe a significant signal or evidence for eta'rho+ and all the eta'K* channels.…
Recent results from the NA48/2 experiment are presented. The $\pi\pi$ scattering lengths $a_0^0$ and $a_0^2$ have been extracted from the cusp in the $M_{00}^2$ distribution of $K^\pm \to \pi^\pm \pi^0 \pi^0$ decays and from the $K^\pm \to…
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…
The NA48 experiment at CERN has performed a new measurement of direct CP violation, based on data taken in 1997 by simultaneously collecting K_L and K_S decays into pi0pi0 and pi+pi-. The result for the CP violating parameter…