Observation of Two New $N^{*}$ Resonances in the Decay $\psi (3686)\to p\overline{p}{\pi }^0$

Based on $106\times {10}^6\psi (3686)$ events collected with the BESIII detector at the BEPCII facility, a partial wave analysis of $\psi (3686)\to p\overline{p}{\pi }^0$ is performed. The branching fraction of this channel has been determined to be $B\mathbf{(}\psi (3686)\to p\overline{p}{\pi }^0\mathbf{)}=(1.65\pm 0.03\pm 0.15)\times {10}^{-4}$. In this decay, 7 $N^{*}$ intermediate resonances are observed. Among these, two new resonances, $N(2300)$ and $N(2570)$ are significant, one $1/2^{+}$ resonance with a mass of ${2300}_{-30-0}^{+40+109}\mathrm{MeV}/c^2$ and width of ${340}_{-30-58}^{+30+110}\mathrm{MeV}/c^2$, and one $5/2^{-}$ resonance with a mass of ${2570}_{-10-10}^{+19+34}\mathrm{MeV}/c^2$ and width of ${250}_{-24-21}^{+14+69}\mathrm{MeV}/c^2$. For the remaining 5 $N^{*}$ intermediate resonances [$N(1440)$, $N(1520)$, $N(1535)$, $N(1650)$ and $N(1720)$], the analysis yields mass and width values that are consistent with those from established resonances.

Figure 1

(a) Dalitz plot of $\psi (3686)\to p\overline{p}{\pi }^0$, the invariant mass spectra of (b) $p\overline{p}$, (c) $p{\pi }^0$, and (d) $\overline{p}{\pi }^0$. The dashed lines in (b) show the cut at the $J/\psi$ mass region. The crosses represent the experimental data, and the shaded histograms show the background from continuum process and ${\pi }^0$ sideband. The histograms in solid line show the sum of MC prediction and the background.

Figure 2

The contribution of each intermediate resonance in the $p{\pi }^0$ mass spectra. The interferences with other resonances are included. (a) contributions of $N(1440)$, $N(1520)$, $N(1535)$, and $N(1650)$; (b) contributions of $N(940)$, $N(1720)$, $N(2300)$, and $N(2570)$.