Observation of psi(3770)--> pi pi J/psi and Measurement of Gamma_{ee}[psi(2S)]

TL;DR

This paper reports the observation of psi(3770) decays into J/psi with pion pairs and measures the electronic width of psi(2S) using data from the CLEO detector at CESR.

Contribution

First observation of psi(3770) decays to J/psi with pion pairs and measurement of Gamma_{ee} for psi(2S).

Findings

Branching fractions for psi(3770) decays to pi+pi-J/psi, pi0pi0-J/psi, and eta-J/psi.

Significance levels of observed decay signals.

Measured Gamma_{ee} of psi(2S).

Abstract

We observe signals for the decays psi(3770)--> X J/psi from data acquired with the CLEO detector operating at the CESR e^+e^- collider with sqrt{s}=3773 MeV. We measure the following branching fractions B(psi(3770)--> XJ/psi) and significances: (189 +- 20 +- 20) x 10^-5 (11.6sigma) for X=pi^+pi^-, (80 +- 25 +- 16) x 10^-5 (3.4sigma) for X=pi^0pi^0, and (87 +- 33 +- 22) x 10^-5 (3.5sigma) for X=eta, where the errors are statistical and systematic, respectively. The radiative return process e^+e^- -->gamma psi(2S) populates the same event sample and is used to measure Gamma_{ee}[psi(2S)]=(2.54 +- 0.03 +- 0.11) keV.