Dergi makalesi Açık Erişim

Measurement of the cross sections for ${e}^{+}{e}^{-}\to \eta {\pi }^{+}{\pi }^{-}$ at center-of-mass energies between 2.00 and 3.08 GeV

2023    CERN İşbirliği

Using data samples collected at center-of-mass energies between 2.000 and 3.080 GeV with the BESIII detector operating at the BEPCII collider, a partial-wave analysis is performed on the process ${e}^{+}{e}^{-}\to \eta {\pi }^{+}{\pi }^{-}$. In addition to the dominant ${e}^{+}{e}^{-}\to \rho \eta $ component, the ${e}^{+}{e}^{-}\to {a}_{2}\left(1320\right)\pi $ process is also sizable, contributing up to 24% of the total reaction. The measured cross sections of the process ${e}^{+}{e}^{-}\to \eta {\pi }^{+}{\pi }^{-}$ are systematically higher than those of BABAR by more than $3\sigma $ at center-of-mass energies between 2.000 and 2.300 GeV. In the cross section line shape for ${e}^{+}{e}^{-}\to {a}_{2}\left(1320\right)\pi $, a resonant structure is observed with a significance of $5.5\sigma $, with $M=\left(2044±31±4\right)\text{}\text{}\mathrm{MeV}/{c}^{2}$, $\Gamma =\left(163±69±24\right)\text{}\text{}\mathrm{MeV}$, and ${B}_{R}·{\Gamma }_{{e}^{+}{e}^{-}}^{R}=\left(34.6±17.1±6.0\right)\text{}\text{}\mathrm{eV}$ or $\left(137.1±73.3±2.1\right)\text{}\text{}\mathrm{eV}$. In the cross section line shape for ${e}^{+}{e}^{-}\to \rho \eta $, an evidence of a dip structure around $2180\text{}\text{}\mathrm{MeV}/{c}^{2}$ is observed with statistical significance of $3.0\sigma $.