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

TL;DR

This paper reports the first measurements of cross sections for specific multi-pion and pion-eta final states in electron-positron collisions from threshold to 4.5 GeV, using initial-state radiation data from BaBar.

Contribution

It provides the first-ever measurements of these cross sections and observes J/ψ and ψ(2S) decays into these states, many of which are measured for the first time.

Findings

First measurements of the cross sections for $e^+e^- o ext{multi-pion states}$.

Observation of J/ψ and ψ(2S) decays into these final states.

Identification of intermediate states like ωπ^0π^0π^0, ηπ^+π^-π^0, ωη.

Abstract

We study the processes $e^+e^-\to\pi^+\pi^-\pi^0\pi^0\pi^0\pi^0\gamma$ and $e^+e^-\to\pi^+\pi^-\pi^0\pi^0\pi^0\eta\gamma$ in which an energetic photon is radiated from the initial state. The data were collected with the BaBar detector at the SLAC National Accelerator Laboratory. About 7300 and 870 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 $e^+e^-$ 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 $e^+e^-\to\pi^+\pi^-\pi^0\pi^0\pi^0\pi^0$ and the $e^+e^-\to\pi^+\pi^-\pi^0\pi^0\pi^0\eta$ cross sections are performed. The contributions from $\omega\pi^0\pi^0\pi^0$, $\eta\pi^+\pi^-\pi^0$, $\omega\eta$, 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.