First observation and study of the $K^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu$ decay

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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. The 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. 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 $(3.45 \pm 0.16) \times 10^{-6}$, in agreement with chiral perturbation theory predictions. Batley, John Richard; Kalmus, George; Lazzeroni, Cristina; Munday, David John; Slater, Mark W.; Wotton, Stephen A.; Arcidiacono, Roberta; Bocquet, Ginette; Cabibbo, Nicola; Ceccucci, Augusto; Cundy, Donald; Falaleev, Valeri; Fidecaro, Maria; Gatignon, Lau; Gonidec, Allain; Kubischta, Werner; Maier, Andrew; Norton, Alan; Patel, Mitesh; Peters, Andreas Joachim; Potrebenikov, Yuri; Monnier, Emmanuel; Swallow, Earl; Winston, Roland; Rubin, Philip David; Walker, Alan; Dalpiaz, Pietro; Damiani, Chiara; Fiorini, Massimiliano; Martini, Mara; Petrucci, Ferruccio; Savrié, Mauro; Scarpa, Marcella; Wahl, Heinrich; Baldini, Wander; Cotta Ramusino, Angelo; Gianoli, Alberto; Calvetti, Mario; Celeghini, Enrico; Iacopini, Enrico; Lenti, Massimo; Ruggiero, Giuseppe; Bizzeti, Andrea; Veltri, Michele; Behler, Matthias; Eppard, Kirsten; Hita-Hochgesand, Manuel; Kleinknecht, Konrad; Marouelli, Peter; Masetti, Lucia; Moosbrugger, Ulrich; Morales Morales, Cristina; Renk, Burkhard; Wache, Martin; Wanke, 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First observation and study of the $K^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu$ decay - CERN Document Server