Precision measurement of the branching fractions of J/psi -> pi+pi-pi0 and psi' -> pi+pi-pi0

TL;DR

This paper precisely measures the branching fractions of J/psi and psi' decays to pi+pi-pi0, revealing different decay dynamics and intermediate states with detailed spectra and Dalitz plots.

Contribution

It provides the most precise measurements to date of these branching fractions and analyzes the decay mechanisms and intermediate states involved.

Findings

J/psi -> pi+pi-pi0 branching fraction measured as (2.137 +- 0.004 (stat.) +0.058-0.056 (syst.) +0.027-0.026 (norm.))*10-2

psi' -> pi+pi-pi0 branching fraction measured as (2.14 +- 0.03 (stat.) +0.08-0.07 (syst.) +0.09-0.08 (norm.))*10-4

J/psi decay dominated by rho(770) intermediate state, psi' decay shows di-pion mass around 2.2 GeV/c2.

Abstract

We study the decays of the J/psi and psi' mesons to pi+pi-pi0 using data samples at both resonances collected with the BES III detector in 2009. We measure the corresponding branching fractions with unprecedented precision and provide mass spectra and Dalitz plots. The branching fraction for J/psi -> pi+pi-pi0 is determined to be (2.137 +- 0.004 (stat.) +0.058-0.056 (syst.) +0.027-0.026 (norm.))*10-2, and the branching fraction for psi' -> pi+pi-pi0 is measured as (2.14 +- 0.03 (stat.) +0.08-0.07 (syst.) +0.09-0.08 (norm.))*10-4. The J/psi decay is found to be dominated by an intermediate rho(770) state, whereas the psi' decay is dominated by di-pion masses around 2.2 GeV/c2, leading to strikingly different Dalitz distributions.