Related papers: New physics limits from kaon decays
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,…
Kaon physics provides a unique opportunity to identify new flavour and CP violating interactions beyond the Standard Model (SM). In the SM, implied by the hierarchical structure of the CKM matrix and the GIM mechanism, flavour changing…
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 availability of high-intensity kaon beams at the J-PARC Hadron Experimental Facility and the CERN SPS North Area, together with the abundant forward production of kaons at the LHC, gives rise to unique possibilities for sensitive tests…
The NA62 experiment at CERN will measure the branching ratio of the K+ -> pi+ nu nubar decay with a precision of 10%, collecting about 100 events in two years of run. This paper will review the design of the experiment, the strategy for the…
Recent results and future prospects of the particle physics experiments with neutral and charged K-meson (kaon) decays are reviewed. Topics include CP violation, rare decays, leptons in kaon decays, tests of CPT and quantum mechanics,…
The first lattice result from the RBC and UKQCD Collaborations and improved perturbative calculations of $\varepsilon^{\prime}_K / \varepsilon_K$ have implied that the Standard-Model (SM) expectation deviates from measured values at the…
Dedicated experiments searching for lepton flavour violation can be performed very sensitively using K-decays and $\mu$-decays as well as neutrinoless double $\beta$-decay and muonium to antimuonium conversion. Although there is no…
The NA48/2 Collaboration at CERN has accumulated unprecedented statistics of rare kaon decays in the Ke4 modes: Ke4(+-) ($K^\pm \to \pi^+ \pi^- e^\pm \nu$) and Ke4(00) ($K^\pm \to \pi^0 \pi^0 e^\pm \nu$) with nearly one percent background…
A sample of 7253 $K^\pm\to\pi^\pm e^+e^-$ decay candidates with 1.0% background contamination has been collected by the NA48/2 experiment at the CERN SPS, which allowed a precise measurement of the form factor, the branching ratio, and the…
A precision test of lepton universality by measurement of the ratio RK of K-->e nu to K-->mu nu decay rates was performed using a sample of 59963 K-->e nu candidates with 8.8% background contamination collected by the CERN NA62 experiment.…
Recent results and future prospects of rare kaon-decay experiments at KEK, BNL, CERN and FNAL are reviewed. Topics include lepton flavor violation, T-violating transverse muon polarization in K+{mu3}, exotic decays, K0 -> pi0 ell+ ell-, and…
We report the recent results on rare kaon decays from the NA48/2 experiment. The precise measurement of direct photon emission (DE) in the decay K+- -> pi+- pi0 gamma and its interference (INT), with the INT amplitude being observed for the…
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 NA48/2 experiment at CERN reports the first observation of the $K^\pm \to \pi^\pm \pi^0 e^+ e^-$ decay from an exposure of $1.7 \times 10^{11}$ charged kaon decays recorded in $2003-2004$. A sample of 4919 candidates with 4.9%…
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,…
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…
Heavy neutral leptons (HNLs) appear in many extensions of the Standard Model of particle physics. In this study, we investigate to which extent the NA62 experiment at CERN could improve the existing bounds on the HNL mixing angle $|U_e|^2$…
The Fermilab KTeV experiment has searched for lepton flavor violating decays of the KL meson in three decay modes. We observe no events in the signal region for any of the modes studied, and we set the following upper limits for their…
During the last fifteen years B_{s,d} decays, B_{s,d}^0-\bar B^0_{s,d} mixings, CP-violating asymmetries S_{\psi K_S} and S_{\psi\phi} provided the dominant information about the pattern of flavour violation within the SM and its…