Precise measurement of the K±→π±e+e− decay

J.r. Batley, C. Lazzeroni, E. Goudzovski, A. Winhart, S. Bifani, NA48/2 collaboration

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A sample of 7253 K±→π±e+e−(γ) decay candidates with 1.0% background contamination has been collected by the NA48/2 experiment at the CERN SPS, which allowed a precise measurement of the decay properties. The branching ratio in the full kinematic range was measured to be BR=(3.11±0.12)×10−7, where the uncertainty includes also the model dependence. The shape of the form factor W(z), where z=2(Mee/MK), was parameterized according to several models, and, in particular, the slope δ of the linear form factor W(z)=W0(1+δz) was determined to be δ=2.32±0.18. A possible CP violating asymmetry of K+ and K− decay widths was investigated, and a conservative upper limit of 2.1×10−2 at 90% CL was established.
Original languageEnglish
Pages (from-to)246-254
Number of pages9
JournalPhysics Letters B
Issue number5
Publication statusPublished - 29 Jun 2009


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