## Abstract

This Letter reports on a new high precision measurement of the form factors of the K_{L} → π^{±} μ^{∓} ν_{μ} decay. The data sample of about 2.3 × 10^{6} events was recorded in 1999 by the NA48 experiment at CERN. Studying the Dalitz plot density we measured a linear, λ_{+} ^{′} = (20.5 ± 2.2_{stat} ± 2.4_{syst}) × 10^{-3}, and a quadratic, λ_{+} ^{″} = (2.6 ± 0.9_{stat} ± 1.0_{syst}) × 10^{-3} term in the power expansion of the vector form factor. No evidence was found for a second order term for the scalar form factor; the linear slope was determined to be λ_{0} = (9.5 ± 1.1_{stat} ± 0.8_{syst}) × 10^{-3}. Using a linear fit our results were: λ_{+} = (26.7 ± 0.6_{stat} ± 0.8_{syst}) × 10^{-3} and λ_{0} = (11.7 ± 0.7_{stat} ± 1.0_{syst}) × 10^{-3}. A pole fit of the form factors yields: m_{V} = (905 ± 9_{stat} ± 17_{syst}) MeV / c^{2} and m_{S} = (1400 ± 46_{stat} ± 53_{syst}) MeV / c^{2}.

Original language | English (US) |
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Pages (from-to) | 341-350 |

Number of pages | 10 |

Journal | Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics |

Volume | 647 |

Issue number | 5-6 |

DOIs | |

State | Published - Apr 19 2007 |

## Keywords

- Kaon form factors
- Kaon semileptonic decays

## ASJC Scopus subject areas

- Nuclear and High Energy Physics

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