Constraining the Kπ vector form factor by τ→Kπντ and Kl3 decay data

A subtracted dispersive representation of the Kπ vector form factor, F+Kπ, is used to fit the Belle spectrum of τ→Kπντ decays incorporating constraints from results on Kl3 decays. Through the use of three subtractions, the slope and curvature of F+Kπ are obtained directly from the data yielding λ+′=(25.49±0.31)×10−3 and λ+′=(12.22±0.14)×10−4. The phase-space integrals relevant for Kl3 analyses are calculated. Additionally, from the pole position on the second Riemann sheet the mass and width of the K⁎(892)± are found to be mK⁎(892)±=892.0±0.5MeV and ΓK⁎(892)±=46.5±1.1MeV. Finally, we study the P-wave isospin-1/2 Kπ phase-shift and its threshold parameters.