What can be learned from the Belle spectrum for the decay τ~-→ντ KSπ~-

摘要

A theoretical description of the differential decay spectrum for the decay τ- → ντ KSπ-, which isbased on the contributing Kπ vector and scalar form factors F Kπ+ (s) and F Kπ0 (s) being calculatedin the framework of resonance chiral theory (RχT), additionally imposing constraints from dispersionrelations as well as short distance QCD, provides a good representation of a recent measurementof the spectrum by the Belle Collaboration. Our fit allows to deduce the total branching fractionBτ- →ντ KSπ- = 0.427 ± 0.024 by integrating the spectrum, as well as the K- resonance parametersMK- = 895.3 ± 0.2 MeV and ΓK- = 47.5 ± 0.4 MeV, where the last two errors are statistical only.From our fits, we confirm that the scalar form factor F Kπ0 (s) is required to provide a good description,but we were unable to further constrain this contribution. Finally, from our results for the vector formfactor F Kπ+ (s), we update the corresponding slope and curvature parameters λ+ = (25.2 ± 0.3) × 10-3and λ~+ = (12.9±0.3)×10-4, respectively.