Partial wave analysis of J/psi to p pbar pi0

TL;DR

This paper performs a detailed partial wave analysis of J/psi to p pbar pi0 decays using a large data sample, identifying a missing N* resonance and measuring various properties of nucleon excited states.

Contribution

It provides the first observation of a missing N* resonance in J/psi decays and measures its properties, advancing understanding of nucleon excitations.

Findings

Observation of a new N* resonance at 2040 MeV/c^2

Determination of the branching fraction for J/psi to p pbar pi0

Measurement of masses, widths, and spin-parities of N* states

Abstract

Using a sample of 58 million $J/\psi$ events collected with the BESII detector at the BEPC, more than 100,000 $J/\psi \to p\bar p \pi^0$ events are selected, and a detailed partial wave analysis is performed. The branching fraction is determined to be $Br(J/\psi \to p \bar p \pi^0)=(1.33 \pm 0.02 \pm 0.11) \times 10^{-3}$. A long-sought `missing' $N^*$, first observed in $J/\psi \to p \bar n \pi^-$, is observed in this decay too, with mass and width of $2040_{-4}^{+3}\pm 25$ MeV/c$^2$ and $230_{-8}^{+8}\pm 52$ MeV/c$^2$, respectively. Its spin-parity favors ${3/2}^+$. The masses, widths, and spin-parities of other $N^*$ states are obtained as well.