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Batley, J.R.; Culling, A.J.; Kalmus, G.; Lazzeroni, C.; Munday, D.J.; Slater, M.W.; Wotton, S.A.; Bocquet, G.; Ceccucci, A.; Cundy, D.; Falaleev, V.; Fidecaro, M.; Gatignon, L.; Norton, A.; Maier, A.; Peters, A.; Balev, S.; Frabetti, P.L.; Goudzovski, E.; Hristov, P.; Kozhuharov, V.; Litov, L.; Madigozhin, D.; Marinova, E.; Molokanova, N.; Polenkevich, I.; Potrebenikov, Y.; Stoynev, S.; Monnier, E.; Winston, R.; Rubin, P.; Walker, A.; Baldini, W.; Dalpiaz, P.; Damiani, C.; Fiorini, M.; Gianoli, A.; Martini, M.; Savrié, M.; Scarpa, M.; Wahl, H.; Bizzeti, A.; Celeghini, E.; Iacopini, E.; Lenti, M.; Martelli, F.; Ruggiero, G.; Veltri, M.; Behler, M.; Eppard, K.; Marouelli, P.; Masetti, L.; Morales Morales, C.; Renk, B.; Wanke, R.; Winhart, A.; Coward, D.; Fonseca Martin, T.; Shieh, M.; Szleper, M.; Velasco, M.; Imbergamo, E.; Nappi, A.; Pepe, M.; Petrucci, M.C.; Raggi, M.; Valdata-Nappi, M.; Cerri, C.; Collazuol, G.; Costantini, F.; DiLella, L.; Doble, N.; Fantechi, R.; Fiorini, L.; Giudici, S.; Lamanna, G.; Mannelli, I.; Michetti, A.; Sozzi, M.; Bloch-Devaux, B.; Cheshkov, C.; Chèze, J.B.; De Beer, M.; Derré, J.; Marel, G.; Mazzucato, E.; Peyaud, B.; Holder, M.; Ziolkowski, M.; Bifani, S.; Biino, C.; Cartiglia, N.; Clemencic, M.; Goy Lopez, S.; Marchetto, F.; Dibon, H.; Markytan, M.; Mikulec, I.; Neuhofer, G.; Widhalm, L.
The European physical journal. C, Particles and fields, 04/2008, Letnik: 54, Številka: 3Journal Article
We report results from a new measurement of the K e4 decay K ± →π + π - e ± ν by the NA48/2 collaboration at the CERN SPS, based on a partial sample of more than 670 000 K e4 decays in both charged modes collected in 2003. The form factors of the hadronic current (F,G,H) and ππ phase difference (δ=δ s -δ p ) have been measured in ten independent bins of the ππ mass spectrum to investigate their variation. A sizeable acceptance at large ππ mass, a low background and a very good resolution contribute to an improved experimental accuracy, a factor two better than in the previous measurement, when extracting the ππ scattering lengths a 0 0 and a 0 2 . Under the assumption of isospin symmetry and using numerical solutions of the Roy equations, the following values are obtained in the plane (a 0 0 ,a 0 2 ): a 0 0 =0.233±0.016stat±0.007syst,a 0 2 =-0.0471±0.011stat±0.004syst. The presence of potentially large isospin effects is also considered and will allow comparison with precise predictions from Chiral Perturbation Theory.
