Abstract.
The recently published E865 data on charged K_{e4} decays and \(\pi\pi\) phases are reanalyzed to extract values of the two S-wave scattering lengths, of the subthreshold parameters \(\alpha\) and \(\beta\), of the low-energy constants \(\bar{\ell}_3\) and \(\bar{\ell}_4\) as well as of the main two-flavour order parameters: \(\langle\bar uu\rangle\) and \(F_{\pi}\) in the limit \(m_u = m_d = 0\) taken at the physical value of the strange quark mass. Our analysis is exclusively based on direct experimental information on \(\pi\pi\) phases below 800 MeV and on the new solutions of the Roy equations by Ananthanarayan et al. The result is compared with the theoretical prediction relating 2a 0 0-5a 0 2 and the scalar radius of the pion, which was obtained in two-loop Chiral Perturbation Theory. A discrepancy at the 1-\(\sigma\) level is found and commented upon.
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Received: 11 December 2001 / Revised version: 28 March 2002 / Published online: 7 June 2002
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Descotes, S., Fuchs, N., Girlanda, L. et al. Analysis and interpretation of new low-energy \(\pi\pi\) scattering data. Eur. Phys. J. C 24, 469–483 (2002). https://doi.org/10.1007/s10052-002-0965-3
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DOI: https://doi.org/10.1007/s10052-002-0965-3