Study of ${\mathrm{e}}^{+}{\mathrm{e}}^{-}\to \mathrm{p}\overline{\mathrm{p}}{\pi }^0$ in the vicinity of the $\psi (3770)$

The process $e^{+}{e}^{-}\to p\overline{p}{\pi }^0$ has been studied by analyzing data collected at $\sqrt{s}=3.773\mathrm{GeV}$, at $\sqrt{s}=3.650\mathrm{GeV}$, and during a $\psi (3770)$ line shape scan with the BESIII detector at the BEPCII collider. The Born cross section of $p\overline{p}{\pi }^0$ in the vicinity of the $\psi (3770)$ is measured, and the Born cross section of $\psi (3770)\to p\overline{p}{\pi }^0$ is extracted considering interference between resonant and continuum production amplitudes. Two solutions with the same probability and a significance of $1.5\sigma$ are found. The solutions for the Born cross section of $\psi (3770)\to p\overline{p}{\pi }^0$ are $33.8\pm 1.8\pm 2.1\mathrm{pb}$ and ${0.06}_{-0.04-0.01}^{+0.10+0.01}\mathrm{pb}$ ($<0.22\mathrm{pb}$ at a 90% confidence level). Using the estimated cross section and a constant decay amplitude approximation, the cross section $\sigma (p\overline{p}\to \psi (3770){\pi }^0)$ is calculated for the kinematic situation of the planned $\overline{\mathrm{P}}\text{ANDA}$ experiment. The maximum cross section corresponding to the two solutions is expected to be less than 0.79 nb at 90% confidence level and $122\pm 10\mathrm{nb}$ at a center-of-mass energy of 5.26 GeV.

Figure 1

(a) Distribution of the invariant mass $\mathrm{M}(\overline{p}{\pi }^0)$, (b) Dalitz plot of ${\mathrm{M}}^2(p{\pi }^0)$ vs ${\mathrm{M}}^2(\overline{p}{\pi }^0)$, (c) ratio of data and phase-space distributed signal Monte Carlo (MC) for $\cos \theta$ of ${\pi }^0$ candidates, and (d) invariant mass $\mathrm{M}(p{\pi }^0)$, of all candidate events passing the event selection.

Figure 2

The calculated Born cross sections in $e^{+}{e}^{-}$ annihilation to $p\overline{p}{\pi }^0$ at different energy points and the solution of the fitting procedure. The curve of both fit solutions is identical.