Precision measurement of the ratio BR(KS->pi+pi-e+e-) / BR(KL->pi+pi-pi0D)

Batley, J. R.; Kalmus, G. E.; Lazzeroni, C.; Munday, D. J.; Patel, M.; Slater, M. W.; Wotton, S. A.; Arcidiacono, R.; Bocquet, G.; Ceccucci, A.; 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.; Goudzovski, E.; Hristov, P.; Kekelidze, V.; Kozhuharov, V.; Litov, L.; Madigozhin, D.; Molokanova, N.; Potrebenikov, Y. U.; Stoynev, S.; Zinchenko, A.; Monnier, E.; Swallow, E. C.; 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, Andrea; Lenti, M.; Veltri, M.; Behler, M.; Eppard, K.; Eppard, M.; Hirstius, A.; Kleinknecht, K.; Koch, U.; Marouelli, P.; Masetti, L.; Moosbrugger, U.; Morales Morales, C.; Peters, A.; Wanke, R.; Winhart, A.; Dabrowski, A.; Fonseca Martin, T.; Szleper, M.; Velasco, M.; Anzivino, G.; Imbergamo, E.; Lamanna, G.; 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.; Chèze, J. B.; 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.; Goy Lopez, S.; Menichetti, E.; Pastrone, N.; Wislicki, W.; Dibon, H.; Jeitler, M.; Markytan, M.; Neuhofer, G.; Widhalm, L.

doi:10.1016/j.physletb.2010.10.008

The K S → pi+ pi- e+ e- decay mode was investigated using the data collected in 2002 by the NA48/1 Collaboration. With about 23k K S → pi+ pi- e+ e- events and 59k K L → pi+ pi- pi0D normalization decays, the K S → pi+ pi- e+ e- branching ratio relative to the K L → pi+ pi- pi0D one was determined to be BR( K S → pi+ pi- e+ e- )/BR( K L → pi+ pi- pi0D ) = (3.28 ± 0.06stat ± 0.04syst ) × 10^−2 . This result was used to set the upper limit | g(E1) / g(BR) | < 3.0 at 90% CL on the presence, in the decay amplitude, of an E1 direct emission g(E1) term relative to the dominant inner bremsstrahlung g(BR) term. The CP-violating asymmetry Aφ in the sin φ cos φ distribution of K S → pi+ pi- e+ e- events, where φ is the angle between the pi+ pi- 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 K S → pi+ pi- e+ e- decay amplitude dominated by the CP-even inner bremsstrahlung process.

Precision measurement of the ratio BR(KS->pi+pi-e+e-) / BR(KL->pi+pi-pi0D) / J. R., B., G. E., K., C., L., D. J., M., M., P., M. W., S., S. A., W., R., A., G., B., A., C., D., C., N., D., V., F., L., G., A., G., P., G., W., K., F., M., I., M., A., N., et al.. - In: PHYSICS LETTERS. SECTION B. - ISSN 0370-2693. - STAMPA. - 694:4-5(2011), pp. 301-309. [10.1016/j.physletb.2010.10.008]