First observation and study of the K±→π0π0μ±νK^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu decay

International audienceThe NA48/2 experiment at CERN reports the first observation of the K$^{±}$ → π$^{0}$π$^{0}$μ$^{±}$ν decay based on a sample of 2437 candidates with 15% background contamination collected in 2003–2004. The decay branching ratio in the kinematic region of the squared dilepton mass above 0.03 GeV$^{2}$/c$^{4}$ is measured to be (0.65 ± 0.03) × 10$^{−6}$. The extrapolation to the full kinematic space, using a specific model, is found to be (3.45 ± 0.16) × 10$^{−6}$, in agreement with chiral perturbation theory predictions

Measurement of the form factors of charged kaon semileptonic decays

International audienceA measurement of the form factors of charged kaon semileptonic decays is presented, based on 4.4 × 10$^{6}$K$^{±}$ → π$^{0}$e$^{±}$ν$_{e}$ (K$_{e3}^{±}$ ) and 2.3 × 10$^{6}$K$^{±}$ → π$^{0}$μ±ν$_{μ}$ (K$_{μ3}^{±}$ ) decays collected in 2004 by the NA48/2 experiment. The results are obtained with improved precision as compared to earlier measurements. The combination of measurements in the K$_{e3}^{±}$ and K$_{μ3}^{±}$ modes is also presented

First observation and study of the K±→π0π0μ±νK^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu decay

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 ratio in the kinematic region of the squared dilepton mass above $0.03$~GeV$^2/c^4$ is measured to be $(0.65 \pm 0.03) \times 10^{-6}$. The extrapolation to the full kinematic space, using a specific model, is found to be $(3.45 \pm 0.17) \times 10^{-6}$, in agreement with chiral perturbation theory predictions