1. New high statistics measurement of Ke4 decay form factors and ππ scattering phase shifts
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P. L. Frabetti, P. Marouelli, A. Michetti, P. Rubin, E. Iacopini, G. Marel, W. Baldini, B. Renk, Andrea Bizzeti, M. Holder, F. Marchetto, R. Fantechi, Milene Calvetti, Simone Bifani, H. Dibon, S. Balev, M. Martini, Mauro Raggi, Michael Ziolkowski, L. Widhalm, U. Moosbrugger, S. Stoynev, E. Marinova, J.B. Cheze, M. Veltri, Luca Fiorini, E. Monnier, G. Neuhofer, A. Maier, A. Norton, Roland Winston, Maulik R. Patel, P. F. Dalpiaz, Massimiliano Fiorini, H. D. Wahl, C. Morales Morales, D.C. Cundy, M. Fidecaro, Rainer Wanke, M. Pepe, G. Kalmus, A. Peters, Manfred Jeitler, S. Goy Lopez, B. Peyaud, G.M. Pierazzini, G. Ruggiero, V. Falaleev, Konrad Kleinknecht, I. Mannelli, N. A. Molokanova, G. Anzivino, M. Szleper, A. Gonidec, Cristina Biino, Ivan Mikulec, M. Scarpa, K. Eppard, D. Coward, Augusto Ceccucci, C. Cheshkov, A. J. Culling, E. C. Swallow, G. Collazuol, M. Valdata-Nappi, A. Cotta Ramusino, W. Kubischta, Evgueni Goudzovski, S. Giudici, D. J. Munday, A. Nappi, E. Imbergamo, B. Vallage, Peter Zahariev Hristov, Mayda Velasco, M. Sozzi, G. Lamanna, Fabrizio Petrucci, Lucia Masetti, S. A. Wotton, Vladimir Kekelidze, M. Slater, L. DiLella, Leander Litov, Enrico Celeghini, M. Wache, D. T. Madigozhin, A. Dabrowski, M. C. Petrucci, E. Mazzucato, Alan W. Walker, M. Markytan, M. Lenti, A. I. Zinchenko, A. Gianoli, Nicola Cabibbo, V. Kozhuharov, M. Savrie, B. Bloch-Devaux, M. De Beer, M. Behler, N. Doble, C. Damiani, Jacqueline Batley, I. Polenkevich, C. Cerri, M. D. Wood, G. Bocquet, Yu. Potrebenikov, F. Martelli, Nicolo Cartiglia, Cristina Lazzeroni, F. Costantini, M. Shieh, A. Winhart, T. Fonseca Martin, Mauro Piccini, Marco Clemencic, Lau Gatignon, P. Cenci, J. Derre, Roberta Arcidiacono, Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and NA48
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DIRECT CP-VIOLATION ,Particle physics ,Chiral perturbation theory ,Meson ,Physics and Astronomy (miscellaneous) ,BEAM ,01 natural sciences ,Nuclear physics ,Particle decay ,Effective mass (solid-state physics) ,Pion ,teoria perturbativa chirale ,SEARCH ,0103 physical sciences ,EQUATION ,[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex] ,decadimenti mesoni K ,scattering lengths ,Engineering (miscellaneous) ,010306 general physics ,mesons ,Elastic scattering ,Physics ,mesoni K ,decadimento Ke4 ,fattori di forma ,pion pion scattering ,PHOTOS MONTE-CARLO ,KE4 DECAYS ,Kaon decay ,pions ,010308 nuclear & particles physics ,13.20.Eb ,13.75.Lb ,Form factor (quantum field theory) ,Isospin ,NA48 ,Particle Physics - Experiment - Abstract
We report results from a new measurement of the $K_{e4}$ decay $K^{\pm} \rightarrow \pi^{+}\pi^{-}e^{\pm}\nu$ by the NA48/2 collaboration at the CERN SPS, based on a partial sample of more than 670000 $K_{e4}$ decays in both charged modes collected in 2003. The form factors of the hadronic current (F, G, H) and $\pi\pi$ phase difference ($\delta=\delta_{s}-\delta_{p}$) have been measured in ten independent bins of the $\pi\pi$ mass spectrum to investigate the variation. A sizeable acceptance at large $\pi\pi$ 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 $\pi\pi$ scattering lengths $a^{0}_{0}$ and $a^{2}_{0}$. Under the assumption of isospin symmetry and using numerical solutions of the Roy equations, the following values are obtained in the plane ($a^{0}_{0}, a^{2}_{0}): a^{0}_{0}=0.233 \pm 0.016_{stat} \pm 0.007_{syst}, a^{2}_{0}=-0.0471 \pm 0.011_{stat} \pm 0.004_{syst}$. The presence of potentially large isospin effects is also considered and will allow comparison with precise predictions from Chiral Perturbation Theory.
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