Related papers: Kaon experiments at CERN: NA48 and NA62
The decay $K^+\to\pi^+\nu\bar{\nu}$ is highly suppressed in the Standard Model (SM), while its rate can be predicted with minimal theoretical uncertainty. The branching ratio (BR) for this decay is thus a sensitive probe of the flavor…
New measurements of K_L and K_S decays from the NA48 experiment are presented. From data taken in the year 2001, the value of the K_e3 charge asymmetry has been determined to delta_L(e) = (3.317 +- 0.070(stat) +- 0.072 (syst)) x 10^-3. From…
The ratio R_K=Gamma(Ke2)/Gamma(Kmu2) provides a very powerful probe for the weak interactions structure. This ratio of decay rates is calculated with very high precision within the Standard Model but the corrections due to the presence of…
The NA48/2 experiment at CERN reports the first observation of the $K^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu$ decay based on a sample of 2437 candidates with 15% background contamination collected in 2003--2004. The decay branching…
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).
We report a first, complete lattice QCD calculation of the long-distance contribution to the $K^+\to\pi^+\nu\bar{\nu}$ decay within the standard model. This is a second-order weak process involving two four-Fermi operators that is highly…
The features of the NA62 experiment at the CERN SPS (high intensity setup, trigger system flexibility, high frequency tracking of beam particles, redundant particle identification, and high-efficiency photon vetoes) make NA62 particularly…
A system for determining the purity of liquid krypton employed in the NA62 rare kaon decay experiment at CERN was developed based on the use of a time projection chamber. The attenuation of drifting ionization electrons from absorption of…
The decay rate of $\klpgg$ has been measured with the NA48 detector at the CERN SPS. A total of 2558 $\klpgg$ candidates have been observed with a residual background of 3.2%. The branching ratio is determined to be $(1.36 \pm0.03_{(stat)}…
The NA62 experiment at the CERN SPS reports a study of a sample of $4 \times10^{9}$ tagged $\pi^0$ mesons from $K^+ \to \pi^+ \pi^0 (\gamma)$, searching for the decay of the $\pi^0$ to invisible particles. No signal is observed in excess of…
A timely and long-term programme of kaon decay measurements at a new level of precision is presented, leveraging the capabilities of the CERN Super Proton Synchrotron (SPS). The proposed programme is firmly anchored on the experience built…
This paper reviews the current status of experimental measurements of radiative kaon decays. Several experiments at BNL, CERN and FNAL have recently or will soon complete data collection; as a result, several new results are available.
Recent anomalies in the decays of $B$ mesons and the Higgs boson provide hints towards lepton flavor (universality) violating physics beyond the Standard Model. We observe that four-fermion operators which can explain the $B$-physics…
The NA48/2 experiment at CERN collected two data samples with minimum bias trigger conditions in 2003 and 2004. A measurement of the rate and dynamic properties of the rare decay $K^\pm\to\pi^\pm\gamma\gamma$ from these data sets based on…
The status of rare kaon decay experiments is reviewed. With the current generation of experiments now finishing, several exciting new results are available. New limits in the search for Lepton Flavor Violation (LFV) will be discussed, as…
Rare Kaon decays provide sensitive probes of short distance physics. Among the most promising modes are the K+ --> pi+ nu anti-nu and K(L) --> pi0 nu anti-nu modes due to their theoretical cleanness and the dedicated experiments, NA62 and…
The NA62 experiment at CERN, designed to study the ultra-rare decay $K^+ \to \pi^+\nu\overline{\nu}$, has also collected data in beam-dump mode. In this configuration, dark photons may be produced by protons dumped on an absorber and reach…
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 latest search for the rare kaon decay $K^+\to\pi^+\nu\bar\nu$ by the NA62 experiment has produced evidence for it with a branching fraction consistent with the prediction of the standard model. The new result implies that in this decay,…
We point out that, given the current experimental status of radiative kaon decays, a subclass of the ${\cal O} (p^4)$ counterterms of the weak chiral lagrangian can be determined in closed form. This involves in a decisive way the decay…