Kπ vector form factor constrained by τ → Kπν <inf>τ</inf> and K<inf>l3</inf> decays

D. R. Boito, R. Escribano, M. Jamin

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33 Citations (Scopus)


Dispersive representations of the Kπ vector and scalar form factors are used to fit the spectrum of τ →; Kπ;ντ obtained by the Belle collaboration incorporating constraints from results for Kl3 decays. The slope and curvature of the vector form factor are obtained directly from the data through the use of a three-times-subtracted dispersion relation. We find λ′+ = (25.49 ± 0.31) × 10-3 and λ″+″ = (12.22 ± 0.14) × 10 -4. From the pole position on the second Riemann sheet the mass and width of the K*(892)± are found to be m K*(892)± = 892.0 ± 0.5 MeV and ΓK*(892)± = 46.5 ± 1.1 MeV. The phase-space integrals needed for Kl3 decays are calculated as well. Furthermore, the Kπ isospin-1/2 P-wave threshold parameters are derived from the phase of the vector form factor. For the scattering length and the effective range we find respectively a11/2 = (0.166 ± 0.004) m π-3 and b1/21 = (0.258 ± 0.009) m-5π. © SISSA 2010.
Original languageEnglish
Article number031
JournalJournal of High Energy Physics
Issue number9
Publication statusPublished - 10 Dec 2010


  • Phenomenological models
  • QCD phenomenology


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