Study of the reactions $e^+e^-\to2(\pi^+\pi^-)\pi^0\pi^0\pi^0$ and $e^+e^-\to2(\pi^+\pi^-)\pi^0\pi^0\eta$ at center-of-mass energies from threshold to 4.5 GeV using initial-state radiation

TL;DR

This paper measures the cross sections of specific multi-pion and eta final states in electron-positron collisions from threshold to 4.5 GeV using initial-state radiation, providing first-time measurements and observing charmonium states.

Contribution

It presents the first measurements of the $e^+e^-$ to multi-pion and eta final state cross sections over a wide energy range, including observations of $J/A$ and $ (2S)$ states and their branching fractions.

Findings

First measurements of these cross sections.

Observation of $J/\psi$ and $\psi(2S)$ in the final states.

Many branching fractions measured for the first time.

Abstract

We study the processes $e^+e^-\to 2(\pi^+\pi^-)\pi^0\pi^0\pi^0\gamma$ and $2(\pi^+\pi^-)\pi^0\pi^0\eta\gamma$ in which an energetic photon is radiated from the initial state. The data were collected with the \babar~ detector at SLAC. About 14\,000 and 4700 events, respectively, are selected from a data sample corresponding to an integrated luminosity of 469 fb^{-1}. The invariant mass of the hadronic final state defines the effective \epem center-of-mass energy. The center-of-mass energies range from threshold to 4.5 GeV. From the mass spectra, the first ever measurements of the $e^+e^-\to 2(\pi^+\pi^-)\pi^0\pi^0\pi^0$ and the $e^+e^-\to2(\pi^+\pi^-)\pi^0\pi^0\eta$ cross sections are performed. The contributions from $\omega\pi^+\pi^-\pi^0\pi^0$, $\eta2(\pi^+\pi^-)$, and other intermediate states are presented. We observe the $J/\psi$ and $\psi(2S)$ in most of these final states and measure the corresponding branching fractions, many of them for the first time.