Measurement of the $η$ -$η'$ mixing angle in $π^{-}$ and $K^{-}$ beams with GAMS-$4π$ Setup

Abstract

The results of mixing angle measurement for $η'$, $η$ mesons generated in charge exchange reactions with $π^{-}$ and $K^{-}$ beams are preseneted. When the $η'$, $η$ mesons are described in nonstrange(NS)--strange(S) quark basis the $π^{-}$ and $K^{-}$ beams allow to study $|η_{q}>$ and $|η_{s}>$ parts of the meson wave function. The cross section ratio at $t'=0$ (GeV/c)$^{2}$ in the $π^{-}$ beam is $R_π(η'/η)= 0.56 \pm 0.04$, results in mixing angle $ϕ_{P} = (36.8 \pm 1.)^{o} $. For $K^{-}$ beam the ratio is $R_{K}(η'/η)= 1.30 \pm 0.16$. It was found that gluonium content in $η'$ is $\sin^{2}ψ_{G}= 0.15 \pm 0.06$. The experiment was carried out with GAMS-4$π$ Setup.