The first observation of the K± → π±π0e+e− rare decay by the NA48/2 experiment at CERN SPS is reported, based on ∼ 2 ×1011 K± decays recorded in 2003-2004. From a sample of 4919 candidates with 4.9% background the branching ratio in the full kinematic region is measured to be BR(K± → π±π0e+e−) = (4.24 ±0.14) ×10−6. The study of the kinematic space shows evidence for a structure dependent contribution in agreement with predictions based on Chiral Perturbation Theory. The CP-violating asymmetry between K+ → π+π0e+e− and K− → π−π0e+e− decay rates has been measured, providing an upper limit |ACP| < 4.82 ×10−2 at 90% CL. The NA48/2 combined measurement of the charged kaon semileptonic form factors, based on 4.4 million K± → π0e±νe and 2.3 million K± → π0µ±νµ events collected in 2004, is presented. This result represents the most precise form factor measurement from a combined Kl±3 analysis.
Recent results on Kaon decays from NA48/2 / Bizzeti, A.; Anzivino, G.; Arcidiacono, R.; Baldini, W.; Balev, S.; Batley, J. R.; Behler, M.; Bi-Fani, S.; Biino, C.; Bizzeti, A.; Bloch-Devaux, B.; Bocquet, G.; Cabibbo, N.; Calvetti, M.; Cartiglia, N.; Ceccucci, A.; Cenci, P.; Cerri, C.; Cheshkov, C.; Cheze, J. B.; Clemencic, M.; Collazuol, G.; Costantini, F.; Cotta Ramusino, A.; Coward, D.; Cundy, D.; Dabrowski, A.; Dalpiaz, P.; Damiani, C.; De Beer, M.; Derre, J.; Dibon, H.; Dilella, L.; Doble, N.; Eppard, K.; Falaleev, V.; Fantechi, R.; Fidecaro, M.; Fiorini, L.; Fiorini, M.; Fonseca Martin, T.; Frabetti, P. L.; Gatignon, L.; Gersabeck, E.; Gianoli, A.; Giudici, S.; Gonidec, A.; Goudzovski, E.; Goy Lopez, S.; Hita-Hochgesand, M.; Holder, M.; Hristov, P.; Iacopini, E.; Imbergamo, E.; Jeitler, M.; Kalmus, G.; Kekelidze, V.; Kleinknecht, K.; Kozhuharov, V.; Kubischta, W.; Lamanna, G.; Lazzeroni, C.; Lenti, M.; Litov, L.; Madigozhin, D.; Maier, A.; Mannelli, I.; Marchetto, F.; Marchevski, R.; Marel, G.; Markytan, M.; Marouelli, P.; Martini, M.; Masetti, L.; Mazzucato, E.; Michetti, A.; Mikulec, I.; Misheva, M.; Molokanova, N.; Monnier, E.; Moosbrugger, U.; Morales Morales, C.; Munday, D. J.; Nappi, A.; Neuhofer, G.; Norton, A.; Patel, M.; Pepe, M.; Peters, A.; Petrucci, F.; Petrucci, M. C.; Peyaud, B.; Piccini, M.; Pierazzini, G.; Polenkevich, I.; Potrebenikov, Yu.; Raggi, M.; Renk, B.; Rubin, P.; Ruggiero, G.; Savrie, M.; Scarpa, M.; Shieh, M.; Slater, M. W.; Sozzi, M.; Stoynev, S.; Swallow, E.; Szleper, M.; Valdata-Nappi, M.; Vallage, B.; Velasco, M.; Veltri, M.; Venditti, S.; Wache, M.; Wahl, H.; Walker, A.; Wanke, R.; Widhalm, L.; Winhart, A.; Winston, R.; Wood, M. D.; Wotton, S. A.; Zinchenko, A.; Ziolkowski, M.. - In: POS PROCEEDINGS OF SCIENCE. - ISSN 1824-8039. - 352:(2019), pp. N/A-N/A. (Intervento presentato al convegno 27th International Workshop on Deep-Inelastic Scattering and Related Subjects, DIS 2019 tenutosi a ita nel 2019) [10.22323/1.352.0116].
Recent results on Kaon decays from NA48/2
Bizzeti A.;
2019
Abstract
The first observation of the K± → π±π0e+e− rare decay by the NA48/2 experiment at CERN SPS is reported, based on ∼ 2 ×1011 K± decays recorded in 2003-2004. From a sample of 4919 candidates with 4.9% background the branching ratio in the full kinematic region is measured to be BR(K± → π±π0e+e−) = (4.24 ±0.14) ×10−6. The study of the kinematic space shows evidence for a structure dependent contribution in agreement with predictions based on Chiral Perturbation Theory. The CP-violating asymmetry between K+ → π+π0e+e− and K− → π−π0e+e− decay rates has been measured, providing an upper limit |ACP| < 4.82 ×10−2 at 90% CL. The NA48/2 combined measurement of the charged kaon semileptonic form factors, based on 4.4 million K± → π0e±νe and 2.3 million K± → π0µ±νµ events collected in 2004, is presented. This result represents the most precise form factor measurement from a combined Kl±3 analysis.
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