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

The collaboration
Phys.Rev.D 93 (2016) 012005, 2016.

Abstract (data abstract)
SLAC-PEP2. We study the processes $\gamma \gamma \to K^0_s K^{\pm}\pi^{\mp}$ and $\gamma \gamma \to K^+ K^- \pi^0$ 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 $\Upsilon(nS)$ ($n = 2,3,4$) resonances. We observe $\eta_c$ 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 $I=1/2$ $K \pi$ $\mathcal{S}$-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behaviour 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 $\Gamma=271 \pm 22 \pm 29 \$MeV.

• #### Table 1

Data from Table 5

10.17182/hepdata.76968.v1/t1

Measured amplitude and phase values for the $I=1/2$ $K \pi$ $\mathcal{S}$-wave as functions of mass obtained from the Model Independent...

• #### Table 2

Data from Table 5

10.17182/hepdata.76968.v1/t2

Measured amplitude and phase values for the $I=1/2$ $K \pi$ $\mathcal{S}$-wave as functions of mass obtained from the Model Independent...