Measurement of the $I=1/2$ $K\ensuremath{\pi}\text{ }\mathcal{S}$-wave amplitude from Dalitz plot analyses of ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}K\overline{K}\ensuremath{\pi}$ in two-photon interactions

Measurement of the $I = 1 / 2$ $K π S$ -wave amplitude from Dalitz plot analyses of $η_{c} \to K \bar{K} π$ in two-photon interactions

J. P. Lees et al. (The BaBar Collaboration)

Phys. Rev. D 93, 012005 – Published 20 January 2016

Abstract

We study the processes $γ γ \to K_{S}^{0} K^{\pm} π^{\mp}$ and $γ γ \to K^{+} K^{-} π^{0}$ using a data sample of $519 {fb}^{- 1}$ recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy $e^{+} e^{-}$ collider at center-of-mass energies at and near the $Υ (n S)$ ( $n = 2$ , 3, 4) resonances. We observe $η_{c}$ decays to both final states and perform Dalitz plot analyses using a model-independent partial wave analysis technique. This allows a model-independent measurement of the mass-dependence of the $I = 1 / 2$ $K π S$ -wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behavior for the phase up to a mass of $1.5 GeV / c^{2}$ . In contrast, the amplitudes show very marked differences. The data require the presence of a new $a_{0} (1950)$ resonance with parameters $m = 1931 \pm 14 \pm 22 MeV / c^{2}$ and $Γ = 271 \pm 22 \pm 29 MeV$ .