IFAE 2006 pp 237-241 | Cite as

Charged kaons and Vus at KLOE

  • KLOE collaboration
Conference paper


At the Frascati phi-factory Dafne e + and e beams collide in the center of mass energy of the the φ-meson which decays into anti-collinear K \( \bar K \) pairs. In the laboratory this remains approximately true because of the small crossing angle of the e + e beams. Therefore the detection of a K(\( \bar K \) ) tags the presence of a \( \bar K \) (K) of given momentum and direction. The decay products of the K ± pair define two spatially well separated regions called the tag and the signal hemispheres. Identified K decays tag a K ± beam and provide an absolute count, using the total number of tags as normalization. This procedure is a unique feature of a φ-factory and provides the means for measuring absolute branching ratios. Charged kaons are tagged using the two body decays K ± → μ± v μ and K ±π ± π 0. Since the two body decays correspond to about 85% of the charged kaon decays [4] and since BR(φK + K ) ≃ 49% [4], there are about 1.5 × 106 K + K events/pb−1. The two body decays are identified as peaks in the momentum spectrum of the secondary tracks in the kaon rest frame and in the pion mass hypothesis p*(m π) In order to minimize the impact of the trigger efficiency, the tagging kaon by itself must provide the event trigger (self-trigger).


Body Decay Decay Vertex Kaon Decay Charged Kaon Secondary Track 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Italia 2007

Authors and Affiliations

  • KLOE collaboration
    • 1
  1. 1.Università degli Studi “Federico II” e Sezione INFNNapoli

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