Search for a strangeonium-like structure $Z_s$ decaying into $\varphi \pi$ and a measurement of the cross section $e^{+}{e}^{-}\to \varphi \pi \pi$

Using a data sample of $e^{+}{e}^{-}$ collision data corresponding to an integrated luminosity of 108 pb${}^{-1}$ collected with the BESIII detector at a center-of-mass energy of 2.125 GeV, we study the process $e^+e^-\rightarrow \phi\pi\pi$andsearchforastrangeoniumlikestructure$Z_s$decayinginto$\phi\pi$\mathrm{.}Nosignalisobservedinthe$\phi\pi$ mass spectrum. Upper limits on the cross sections for $Z_s$ production at the 90% confidence level are determined. In addition, the cross sections of $e^{+}{e}^{-}\to \varphi {\pi }^{+}{\pi }^{-}$ and $e^{+}{e}^{-}\to \varphi {\pi }^0{\pi }^0$ at 2.125 GeV are measured to be $(436.2\pm 6.4\pm 30.1)$ pb and $(237.0\pm 8.6\pm 15.4)$ pb, respectively, where the first uncertainties are statistical and the second systematic.