# Measurement of the Ratio $\Gamma(K_L \to \pi^+ \pi^-)/\Gamma(K_L \to \pi\pm e \mp\nu)$ and Extraction of the CP Violation Parameter $|\eta+-|$

Abstract : We present a measurement of the ratio of the decay rates Gamma(KL -> pi+ pi-)/Gamma(KL -> pi e nu), denoted as Gamma(K2pi)/Gamma(Ke3). The analysis is based on data taken during a dedicated run in 1999 by the NA48 experiment at the CERN SPS. Using a sample of 47000 K2pi and five million Ke3 decays, we find Gamma(K2pi)/Gamma(Ke3) = (4.835 +- 0.022(stat) +- 0.016(syst)) x 10^-3. From this we derive the branching ratio of the CP violating decay KL -> pi+ pi- and the CP violation parameter |eta+-|. Excluding the CP conserving direct photon emission component KL -> pi+ pi- gamma, we obtain the results BR(KL -> pi+ pi-) = (1.941 +- 0.019) x 10^-3 and |eta+-| = (2.223 +- 0.012) x 10^-3.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00142530
Contributor : Sabine Starita <>
Submitted on : Thursday, April 19, 2007 - 3:48:25 PM
Last modification on : Tuesday, December 22, 2020 - 12:26:05 PM

### Citation

A. Bevan, R. S. Dosanjh, T. J. Gershon, B. Hay, G. E. Kalmus, et al.. Measurement of the Ratio $\Gamma(K_L \to \pi^+ \pi^-)/\Gamma(K_L \to \pi\pm e \mp\nu)$ and Extraction of the CP Violation Parameter $|\eta+-|$. Physics Letters B, Elsevier, 2007, 645, pp.26-35. ⟨10.1016/j.physletb.2006.11.071⟩. ⟨in2p3-00142530⟩

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