New limit on the K{sub L}°âÏ°νν decay rate (original) (raw)
Related papers
2007
Measured ratios of decay rates for R Ke3/K2π , R Kµ3/K2π and R Kµ3/Ke3 are presented. These measurements are based on K ± decays collected in a dedicated run in 2003 by the NA48/2 experiment at CERN. The results obtained are R Ke3/K2π = 0.2496 ± 0.0009(stat) ± 0.0004(syst) and R Kµ3/K2π = 0.1637 ± 0.0006(stat) ± 0.0003(syst). Using the PDG average for the K ± → π ± π 0 normalisation mode, both values are found to be larger than the current values given by the Particle Data Book and lead to a larger magnitude of the |V us | CKM element than previously accepted. When combined with the latest Particle Data Book value of |V ud |, the result is in agreement with unitarity of the CKM matrix. In addition, a new measured value of R Kµ3/Ke3 = 0.656 ± 0.003(stat) ± 0.001(syst) is compared to the semi-empirical predictions based on the latest form factor measurements.
Proceedings of Flavor Physics and CP Violation — PoS(FPCP2016)
Rare kaon decays are sensitive probes to search for new physics beyond the standard model. This talk reviews the status of J-PARC KOTO and CERN NA62 experiments for the K → πνν decays, J-PARC E36 for the lepton number universality, and CERN LHCb experiment for K S decays.
Measurement of decay using stopped kaons
Physics Letters B, 2006
The K + → π 0 µ + νγ (K µ3γ) decay has been measured with stopped positive kaons at the KEK 12 GeV proton synchrotron. A K µ3γ sample containing 125 events was obtained. The partial branching ratio Br(K µ3γ , E γ > 30 MeV, θ µ + γ > 20 •) was found to be [2.4 ± 0.5(stat) ± 0.6(syst)] × 10 −5 , which is in good agreement with theoretical predictions. 2005 Elsevier B.V.
Recent NA48/2 results on rare kaon decays
EPJ Web of Conferences, 2019
NA48/2 results contributing to ChPT testing are presented. A sample of 1663 events of the rare decay $ K^ \pm \to \mu ^ \pm ve^ + e^ - $ has been selected with a minimume+e−effective mass of 140 MeV. The measured model independent decay rate is in agreement with ChPT predictions. The branching ratio of the $ K^ \pm \to \mu ^ \pm ve^ + e^ - $ decay, never observed so far, has been obtained from a sample of about 5000 candidates with less than 6% background, also in agreement with ChPT predictions. In addition, a most precise measurement of the charged kaon semileptonic formfactors has been obtained from 4.4 millionKe3and 2.3 millionKµ3events collected in 2004.
Rare Kaon Decays K->pi n n and KL->pi l+l
2005
Over the next years, the Flavour Physics community will be looking for inconsistencies of the Standard Model (SM) by exploiting new and precise measurements. In these ``indirect new physics'' searches, the key strategy is to concentrate on observables, which are theoretically clean and preferably suppressed in the SM. In this respect, the four golden modes K+->pi+ n n, KL->pi n n and KL->pi0 l+l- are very promising. The pollution from hadronic uncertainties in these decays is at present under control with good accuracy, thanks to the interplay between theory information (Chiral Perturbation Theory and OPE) and experimental inputs (KTeV, NA48). Their measurements might thus give rise to some unexpected scenario. Here, we briefly review the present situation for these four exclusive rare decays.
Kaon decay studies at CERN SPS in the last decades
Physics of Particles and Nuclei, 2016
This review summarizes the kaon experimental results obtained in the last 15 years on the basis of data collected at the CERN SPS with the participation of JINR physicists. These results contribute essentially to the Standard Model checks and search for its extension, fundamental symmetry violations and low-energy strong interactions theory development. A progress in the experimental technique and prospects for the future results are also discussed.
Experimental study of the decay K_{L}^{0}→π^{0}νν[over ¯]
Physical Review D, 2010
The first dedicated search for the rare neutral-kaon decay K 0 L → π 0 νν has been carried out in the E391a experiment at the KEK 12-GeV proton synchrotron. The final upper limit of 2.6 ×10 −8 at the 90% confidence level was set on the branching ratio for the decay.