With the data samples taken at center-of-mass energies from 2.00 to 3.08 GeV with the BESIII detector at the BEPCII collider, a partial wave analysis on the $e^{ +}e^{ -}\rightarrow\pi^{ +}\pi^{ -}\pi^{ 0}$ process is performed. The Born cross sections for $e^{ +}e^{ -}\rightarrow\pi^{ +}\pi^{ -}\pi^{ 0}$ and its intermediate processes $e^{ +}e^{ -}\rightarrow\rho\pi$ and $\rho(1450)\pi$ are measured as functions of $\sqrt{ s}$. The results for $e^{ +}e^{ -}\rightarrow\pi^{ +}\pi^{ -}\pi^{ 0}$ are consistent with previous results measured with the initial state radiation method within one standard deviation, and improve the uncertainty by a factor of ten. By fitting the line shapes of the Born cross sections for the $e^{ +}e^{ -}\rightarrow\rho\pi$ and $\rho(1450)\pi$, a structure with mass $M = 2119\pm11\pm15\ { \rm MeV}/c^2$ and width $\Gamma=69\pm30\pm5 { \rm MeV}$ is observed with a significance of $5.9\sigma$, where the first uncertainties are statistical and the second ones are systematic. This structure can be intepreteted as an excited $\omega$ state.
Categories: hep-ex