N* and Delta* decays into N pi0 pi0

TL;DR

This study investigates N* and Delta* baryon resonance decays into N pi0 pi0 using photoproduction data, revealing new decay widths and patterns that challenge existing quark model predictions.

Contribution

It provides the first measurements of several partial decay widths for N* and Delta* resonances decaying into N pi0 pi0, and uncovers decay patterns not predicted by current models.

Findings

Decays into Delta(1232) pi dominate in the second resonance region.

The N(ππ)_S wave significantly contributes in the third resonance region.

P_{13}(1720) properties differ from PDG values.

Abstract

Decays of baryon resonances in the second and the third resonance region into N pi0 pi0 are studied by photoproduction of two neutral pions off protons. Partial decay widths of N* and Delta* resonances decaying into Delta(1232) pi, N(\pi\pi)_{S}, N(1440)P_{11} pi, and N(1520)D_{13} pi are determined in a partial wave analysis of this data, and data from other reactions. Several partial decay widths were not known before. Interesting decay patterns are observed which are not even qualitatively reproduced by quark model calculations. In the second resonance region, decays into Delta(1232) pi dominate clearly. The N(\pi\pi)_{S}-wave provides a significant contribution to the cross section, especially in the third resonance region. The P_{13}(1720) properties found here are at clear variance to PDG values.