Abstract
The KS→π+π-e+e- decay mode was investigated using the data collected in 2002 by the NA48/1 Collaboration. With about 23 k KS→π+π-e+e- events and 59 k KL→π+π-πD0 normalization decays, the KS→π+π-e+e- branching ratio relative to the KL→π+π-πD0 one was determined to be BR(KS→π+π-e+e-)/BR(KL→π+π-πD0)=(3.28±0.06stat±0.04syst)×10-2. This result was used to set the upper limit |gE1/gBR|<3.0 at 90% CL on the presence, in the decay amplitude, of an E1 direct emission (gE1) term relative to the dominant inner bremsstrahlung (gBR) term. The CP-violating asymmetry Aø in the sinøcosø distribution of KS→π+π-e+e- events, where ø is the angle between the π+π- and the e+e- decay planes in the kaon centre of mass, was found to be Aø=(-0.4±0.8)%, consistent with zero. These results are in good agreement with a description of the KS→π+π-e+e- decay amplitude dominated by the CP-even inner bremsstrahlung process.
Original language | English (US) |
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Pages (from-to) | 301-309 |
Number of pages | 9 |
Journal | Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics |
Volume | 694 |
Issue number | 4-5 |
DOIs | |
State | Published - Jan 3 2011 |
Keywords
- CP-violating asymmetry
- Direct emission
- Inner bremsstrahlung
- Kaon rare decay
- Neutral kaon radiative decay
ASJC Scopus subject areas
- Nuclear and High Energy Physics