Measurement of the $e^+e^- \to \eta\pi^+\pi^-$ cross section with the SND detector at the VEPP-2000 collider

TL;DR

This paper reports a measurement of the cross section for the process $e^+e^- o ext{eta}\pi^+\pi^-$ using the SND detector at VEPP-2000, combining results from two eta decay modes to improve accuracy.

Contribution

First measurement of the $e^+e^- o ext{eta}\pi^+\pi^-$ cross section in the $ ext{eta} o 3 ext{pi}^0$ decay mode, and combined with previous results for a more precise measurement.

Findings

Cross section measured in the $ ext{eta} o 3 ext{pi}^0$ mode agrees with previous $ ext{eta} o ext{gamma} ext{gamma}$ measurements.

Combined data provides a more accurate cross section in the energy range 1.075-2.000 GeV.

Results are consistent with existing theoretical models and previous experimental data.

Abstract

The $e^+e^- \to \eta\pi^+\pi^-$ cross section is measured at the SND detector in the $\eta$ decay mode $\eta\to 3\pi^0$. The analysis is based on the data sample with an integrated luminosity of 32.7 pb$^{-1}$ collected at the VEPP-2000 $e^+e^-$ collider in the center-of-mass energy range $\sqrt{s}=1.075-2.000$ GeV. The data obtained in the $\eta\to 3\pi^0$ decay mode are found to be in agreement with the previous SND measurements in the $\eta\to \gamma\gamma$ mode. Therefore the measurements in the two modes are combined.