Study of N* Production from J/Psi--> p pbar eta

TL;DR

This paper reports the first partial wave analysis of N* resonances produced in J/psi decays, identifying two well-known states, S11(1535) and S11(1650), with detailed resonance parameters.

Contribution

It provides the first partial wave analysis of N* resonance production from J/psi decays, confirming known states with precise measurements.

Findings

Identification of N* resonances near 1530 MeV and 1650 MeV

Resonance parameters consistent with established S11 states

First partial wave analysis of these resonances in J/psi decays

Abstract

Data are presented on the reaction J/psi--> p pbar eta using 7.8 million J/psi triggers collected by the BEjing Spectrometer (BES). A partial wave analysis is performed. A clear enhancement near the p eta(pbar eta) threshold is observed. It is fitted with a JP=1/2- resonance with mass $M= 1530\pm 10$ MeV and width $\Gamma = 95\pm 25$ MeV. In addition, there is a peak around 1650 MeV with JP=1/2- preferred also, fitted with $M =1647\pm 20$ MeV and $\Gamma = 145^{+80}_{-45}$ MeV. These two N* resonances are believed to be the two well established states, S11(1535) and S11(1650), respectively. It is the first partial wave study of the production of these resonances from J/psi decays.