Measurement of $e^{+}e^{-}\rightarrow\omega\pi^{+}\pi^{-}$ cross section at $\sqrt s = $ 2.000 to 3.080 GeV

TL;DR

This study measures the cross section of the process $e^{+}e^{-} ightarrow ext{omega} ext{pi}^+ ext{pi}^-$ between 2.0 and 3.08 GeV, discovering a new structure near 2.25 GeV with improved precision and significance.

Contribution

The paper provides the first high-precision measurement of the cross section in this energy range and reports the observation of a new resonance structure near 2.25 GeV.

Findings

Observation of a structure near 2.25 GeV with 7.6σ significance.

Measurement of the resonance parameters: mass 2232 ± 19 ± 27 MeV/c², width 93 ± 53 ± 20 MeV.

Detection of a structure with mass 2200 ± 11 ± 17 MeV/c² and width 74 ± 20 ± 24 MeV with 7.9σ significance.

Abstract

A partial wave analysis on the process $e^{+}e^{-}\rightarrow\omega\pi^{+}\pi^{-}$ is performed using 647 pb$^{-1}$ of data sample collected by using the BESIII detector operating at the BEPCII storage ring at center-of-mass (c.m.) energies from 2.000 GeV to 3.080 GeV. The Born cross section of the $e^{+}e^{-}\rightarrow\omega\pi^{+}\pi^{-}$ process is measured, with precision improved by a factor of 3 compared to that of previous studies. A structure near 2.25 GeV is observed in the energy-dependent cross sections of $e^{+}e^{-}\to\omega\pi^{+}\pi^{-}$ and $\omega\pi^{0}\pi^{0}$ with a statistical significance of 7.6$\sigma$, and its determined mass and width are 2232 $\pm$ 19 $\pm$ 27 MeV$/c^{2}$ and 93 $\pm$ 53 $\pm$ 20 MeV, respectively, where the first and second uncertainties are statistical and systematic, respectively. By analyzing the cross sections of subprocesses $e^{+}e^{-}\rightarrow \omega f_{0}(500)$, $\omega f_{0}(980)$, $\omega f_{0}(1370)$, $\omega f_{2}(1270)$, and $b_{1}(1235)\pi$, a structure, with mass M = 2200 $\pm$ 11 $\pm$ 17 MeV/$c^2$ and width $\Gamma$ = 74 $\pm$ 20 $\pm$ 24 MeV, is observed with a combined statistical significance of 7.9$\sigma$. The measured resonance parameters will help to reveal the nature of vector states around 2.25 GeV.