Abstract
We report results from a new measurement of the Ke4 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 Ke4 decays in both charged modes collected in 2003. The form factors of the hadronic current (F,G,H) and ππ phase difference (δ=δs-δp) 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 a0 0 and a0 2. Under the assumption of isospin symmetry and using numerical solutions of the Roy equations, the following values are obtained in the plane (a0 0,a0 2): a0 0=0.233±0.016stat±0.007syst,a0 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.
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13.20.Eb; 13.75.Lb
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Batley, J., Culling, A., Kalmus, G. et al. New high statistics measurement of Ke4 decay form factors and ππ scattering phase shifts . Eur. Phys. J. C 54, 411–423 (2008). https://doi.org/10.1140/epjc/s10052-008-0547-0
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DOI: https://doi.org/10.1140/epjc/s10052-008-0547-0