The kappa in E791 data for D->K-pi-pi

TL;DR

This paper analyzes D->K-pi-pi decay data, demonstrating the necessity of a kappa resonance with an s-dependent width and showing that a point-like production model suffices, challenging previous form factor assumptions.

Contribution

It provides a combined fit to multiple datasets confirming the kappa resonance and refutes the need for a production form factor in D decays.

Findings

The kappa pole position is at 750 - i342 MeV.

The K-pi S-wave is well fitted with a kappa and Ko(1430).

Production is consistent with a point-like process, radius <0.38 fm.

Abstract

A combined fit is made to E791 data on D->K-pi-pi, LASS data on K-pi elastic scattering, and BES II data on J/Psi->K*(890)-K-pi.In all cases, the K-pi S-wave is fitted well with a kappa resonance and Ko(1430); the kappa requires an s-dependent width with an Adler zero near threshold. The pole position of the kappa is at M - iGamma/2 = (750 +30 -55) - i(342 +- 60) MeV. The E791 collaboration fitted their data using a form factor for the production process D->kappa-pi. It is shown that this form factor is not needed. The data require point-like production with an RMS radius <0.38 fm with 95 percent confidence.