The e+ e- --> 3(pi+pi-), 2(pi+pi-pi0) and K+K- 2(pi+pi-) Cross Sections at Center-of-Mass Energies from Production Threshold to 4.5 GeV Measured with Initial-State Radiation

TL;DR

This paper measures the cross sections of specific e+e- annihilation processes involving multiple pions and kaons over energies up to 4.5 GeV using initial-state radiation data from BaBar, providing detailed insights into hadronic production and J/psi decays.

Contribution

First measurement of these specific cross sections over a wide energy range using initial-state radiation data, including J/psi decay observations.

Findings

Cross sections measured with 6-15% uncertainty.

Observation of J/psi in all studied final states.

Branching fractions of J/psi decays into these states determined.

Abstract

We study the processes e+ e- --> 3(pi+pi-)gamma, 2(pi+pi-pi0)gamma and K+ K- 2(pi+pi-)gamma, with the photon radiated from the initial state. About 20,000, 33,000 and 4,000 fully reconstructed events, respectively, have been selected from 232 fb-1 of BaBar data. The invariant mass of the hadronic final state defines the effective e+e- center-of-mass energy, so that these data can be compared with the corresponding direct e+e- measurements. From the 3(pi+pi-), 2(pi+pi-pi0) and K+ K- 2(pi+pi-) mass spectra, the cross sections for the processes e+ e- --> 3(pi+pi-), e+ e- --> 2(pi+pi-pi0) and e+ e- --> K+ K- 2(pi+pi-) are measured for center-of-mass energies from production threshold to 4.5 GeV. The uncertainty in the cross section measurement is typically 6-15%. We observe the J/psi in all these final states and measure the corresponding branching fractions.