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Batley, J.R.; Kalmus, G.E.; Lazzeroni, C.; Patel, M.; Slater, M.W.; Wotton, S.A.; Arcidiacono, R.; Bocquet, G.; Cundy, D.; Doble, N.; Falaleev, V.; Gatignon, L.; Gonidec, A.; Grafström, P.; Kubischta, W.; Marchetto, F.; Mikulec, I.; Norton, A.; Panzer-Steindel, B.; Rubin, P.; Wahl, H.; Hristov, P.; Kekelidze, V.; Kozhuharov, V.; Litov, L.; Madigozhin, D.; Molokanova, N.; Potrebenikov, Yu; Zinchenko, A.; Monnier, E.; Winston, R.; Sacco, R.; Walker, A.; Baldini, W.; Dalpiaz, P.; Frabetti, P.L.; Gianoli, A.; Martini, M.; Petrucci, F.; Savrié, M.; Scarpa, M.; Calvetti, M.; Collazuol, G.; Iacopini, E.; Ruggiero, G.; Bizzeti, A.; Lenti, M.; Veltri, M.; Behler, M.; Eppard, K.; Eppard, M.; Hirstius, A.; Kleinknecht, K.; Koch, U.; Marouelli, P.; Masetti, L.; Moosbrugger, U.; Peters, A.; Wanke, R.; Winhart, A.; Dabrowski, A.; Velasco, M.; Anzivino, G.; Imbergamo, E.; Lubrano, P.; Michetti, A.; Nappi, A.; Piccini, M.; Valdata-Nappi, M.; Cenci, P.; Pepe, M.; Petrucci, M.C.; Cerri, C.; Fantechi, R.; Mannelli, I.; Costantini, F.; Fiorini, L.; Giudici, S.; Pierazzini, G.; Sozzi, M.; Cheshkov, C.; De Beer, M.; Debu, P.; Gouge, G.; Marel, G.; Mazzucato, E.; Peyaud, B.; Vallage, B.; Holder, M.; Maier, A.; Ziolkowski, M.; Biino, C.; Cartiglia, N.; Clemencic, M.; Lopez, S. Goy; Menichetti, E.; Pastrone, N.; Wislicki, W.; Dibon, H.; Jeitler, M.
Physics letters. B, 01/2011, Letnik: 694, Številka: 4-5Journal Article
The KS→π+π−e+e− decay mode was investigated using the data collected in 2002 by the NA48/1 Collaboration. With about 23 k KS→π+π−e+e− events and 59 k KL→π+π−πD0 normalization decays, the KS→π+π−e+e− branching ratio relative to the KL→π+π−πD0 one was determined to be BR(KS→π+π−e+e−)/BR(KL→π+π−πD0)=(3.28±0.06stat±0.04syst)×10−2. This result was used to set the upper limit |gE1/gBR|<3.0 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 Aϕ in the sinϕcosϕ distribution of KS→π+π−e+e− events, where ϕ is the angle between the π+π− and the e+e− decay planes in the kaon centre of mass, was found to be Aϕ=(−0.4±0.8)%, consistent with zero. These results are in good agreement with a description of the KS→π+π−e+e− decay amplitude dominated by the CP-even inner bremsstrahlung process.
