The KS+−e+e− decay mode was investigated using the data collected in 2002 by the NA48/1 collaboration. With about 23,k KS+−e+e− events and 59,k KL+−0D normalization decays, the KS+−e+e− branching ratio relative to the KL+−0D one was determined to be BR(KS+−e+e− )/BR(KL+−0D ) = (328006stat004syst)10−2. This result was used to set the upper limit gE1gBR30 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 calA in the sin,cosdistribution of KS+−e+e− events, where is the angle between the +− and the e+e− decay planes in the kaon centre of mass, was found to be calA=(−04pm08), consistent with zero. These results are in good agreement with a description of the KS+−e+e− decay amplitude dominated by the CP-even inner bremsstrahlung process.
Precision measurement of the ratio BR(KS --> pi+pi-e+e- )/BR(KL -->pi+pi-pi0D )
MENICHETTI, Ezio;
2010-01-01
Abstract
The KS+−e+e− decay mode was investigated using the data collected in 2002 by the NA48/1 collaboration. With about 23,k KS+−e+e− events and 59,k KL+−0D normalization decays, the KS+−e+e− branching ratio relative to the KL+−0D one was determined to be BR(KS+−e+e− )/BR(KL+−0D ) = (328006stat004syst)10−2. This result was used to set the upper limit gE1gBR30 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 calA in the sin,cosdistribution of KS+−e+e− events, where is the angle between the +− and the e+e− decay planes in the kaon centre of mass, was found to be calA=(−04pm08), consistent with zero. These results are in good agreement with a description of the KS+−e+e− decay amplitude dominated by the CP-even inner bremsstrahlung process.
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