Speaker
Evgueni Goudzovski
(University of Birmingham)
Description
The NA48/2 collaboration has accumulated more than one million charged kaon decays to $\pi^+ \pi^- e^\pm \nu$ $(K_{e4}^{+-})$ leading to an improved determination of the branching ratio by a factor of 3 and detailed form factors and $\pi \pi$ scattering studies. Concurrently, about 60000 charged kaon decays to $\pi^0 \pi^0 e^\pm \nu$ $(K_{e4}^{00})$ have been analyzed, increasing the world available statistics by several orders of magnitude. Background contamination at percent level and very good $\pi^0$ reconstruction allow the first accurate measurements of the branching ratio and decay form factor. The achieved precision makes possible the observation of subtle effects such as $\pi^+ \pi^-$ to $\pi^0 \pi^0$ charge exchange scattering below the $2 m_{\pi^+}$ threshold. Decay properties of both Ke4 modes bring new precise inputs to Low Energy QCD studies and can provide stringent tests of Chiral Perturbation Theory predictions.
Primary authors
Dr
Brigitte Bloch-Devaux
(Universita e INFN (IT))
Spasimir Balev
(CERN)
