6 Measurement of the Branching Ratio of the K L → π + π − decay with the KLOE Detector
نویسندگان
چکیده
We present a measurement of the branching ratio of the CP violating decay KL→ ππ performed by the KLOE experiment at the φ factory DAΦNE. We use 328 pb of data collected in 2001 and 2002, corresponding to ∼ 150 million tagged KL mesons. We find BR(KL → ππ) = (1.963 ± 0.012stat. ± 0.017syst.) × 10. This branching ratio measurement is fully inclusive of final-state radiation. Using the above result, we determine the modulus of the amplitude ratio |η+−| to be (2.219 ± 0.013) × 10 and |ǫ| to be (2.216 ± 0.013) × 10. CP violation was discovered in 1964 through the observation of the decay KL→ ππ [1]. The value of BR(KL → ππ) is known today with high accuracy from the results of many experiments, but a recent measurement by KTeV [2] is in disagreement with the value reported by the PDG [3]. In the Standard Model, CP violation is naturally accommodated by a phase in the quark mixing matrix [4,5]. BR(KL→ππ), together with the well known values of BR(KS→ππ), τKS , and τKL, determines the modulus of the amplitude ratio |η+−| =
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