Eur. Phys. J. A (2005) 25: 107-114
https://doi.org/10.1140/epja/i2005-10033-3

Original Article

The kappa in J/Ψ↦K⁺π

Queen Mary, University of London, E1 4NS, London, UK

^* e-mail: D.Bugg@rl.ac.uk

Received: 7 April 2005
Accepted: 16 April 2005
Published online: 24 May 2005

Abstract

BES II data for J/Ψ↦K ^*(890)Kπ reveal a strong κ peak in the Kπ S-wave near threshold. Both magnitude and phase are determined in slices of Kπ mass by interferences with strong K ₀(1430), K ₁(1270) and K ₁(1400) signals. The phase variation with mass agrees within errors with LASS data for Kπ elastic scattering. A combined fit is presented to both BES and LASS data. The fit uses a Breit-Wigner amplitude with an s-dependent width containing an Adler zero. The κ pole is at (760±20(stat)±40(syst)) - i(420±45(stat)±60(syst)) MeV. The S-wave I = 0 scattering length a ₀ = 0.23±0.04 m _π ^-1 is close to the prediction 0.19±0.02 m _π ^-1 of Chiral Perturbation Theory at O(p ⁴).