A sample of 7253 K±→pi±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=(Mee/MK)2, 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.

Precise measurement of the K+- --> pi+-e+e- decay

NORTON, Alan Robert;BALDINI, Wander;COTTA RAMUSINO, Angelo;DALPIAZ, Pietro;FIORINI, Massimiliano;GIANOLI, Alberto;PETRUCCI, Ferruccio Carlo;SAVRIE', Mauro;
2009

Abstract

A sample of 7253 K±→pi±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=(Mee/MK)2, 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.
2009
J. R., Batley; A. J., Culling; G., Kalmus; C., Lazzeroni; D. J., Munday; M. W., Slater; S. A., Wotton; R., Arcidiacono; G., Bocquet; N., Cabibbo; A., Ceccucci; D., Cundy; V., Falaleev; M., Fidecaro; L., Gatignon; A., Gonidec; W., Kubischta; Norton, Alan Robert; A., Maier; M., Patel; A., Peters; S., Balev; P. L., Frabetti; E., Goudzovski; P., Hristov; V., Kekelidze; V., Kozhuharov; L., Litov; D., Madigozhin; E., Marinova; N., Molokanova; I., Polenkevich; Y., Potrebenikov; S., Stoynev; A., Zinchenko; E., Monnier; E., Swallow; R., Winston; P., Rubin; A., Walker; Baldini, Wander; COTTA RAMUSINO, Angelo; Dalpiaz, Pietro; C., Damiani; Fiorini, Massimiliano; Gianoli, Alberto; M., Martini; Petrucci, Ferruccio Carlo; Savrie', Mauro; M., Scarpa; H., Wahl; A., Bizzeti; M., Calvetti; E., Celeghini; E., Iacopini; M., Lenti; F., Martelli; G., Ruggiero; M., Veltri; M., Behler; K., Eppard; K., Kleinknecht; P., Marouelli; L., Masetti; U., Moosbrugger; C., Morales Morales; B., Renk; M., Wache; R., Wanke; A., Winhart; D., Coward; A., Dabrowski; T., Fonseca Martin; M., Shieh; M., Szleper; M., Velasco; M. D., Wood; G., Anzivino; P., Cenci; E., Imbergamo; A., Nappi; M., Pepe; M. C., Petrucci; M., Piccini; M., Raggi; M., Valdata Nappi; C., Cerri; G., Collazuol; F., Costantini; L., Dilella; N., Doble; R., Fantechi; L., Fiorini; S., Giudici; G., Lamanna; I., Mannelli; A., Michetti; G., Pierazzini; M., Sozzi; B., Bloch Devaux; C., Cheshkov; J. B., Chèze; M., De Beer; J., Derré; G., Marel; E., Mazzucato; B., Peyaud; B., Vallage; M., Holder; M., Ziolkowski; S., Bifani; C., Biino; N., Cartiglia; M., Clemencic; S., Goy Lopez; F., Marchetto; H., Dibon; M., Jeitler; M., Markytan; I., Mikulec; G., Neuhofer; L., Widhalm
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