Observation of the phi to pi+pi-pi+pi- Decay

TL;DR

This study measures the rare phi meson decay into four pions, observing interference effects and setting upper limits on related decay modes, using data from the CMD-2 detector near 1 GeV.

Contribution

First observation of interference pattern in phi to four-pion decay energy dependence and precise measurement of its branching ratio.

Findings

Measured Br(phi to pi+pi-pi+pi-) = (3.93 ± 1.74 ± 2.14) × 10^{-6}

Observed interference pattern near the phi meson energy

Set upper limits for phi decays to five pions and eta pi+pi-

Abstract

Using 11.6 pb^{-1} of data collected in the energy range 0.984--1.06 GeV by CMD-2 at VEPP-2M, the cross section of the reaction e+e- to pi+pi-pi+pi- has been studied. For the first time an interference pattern was observed in the energy dependence of the cross section near the phi meson. The branching ratio of the phi to pi+pi-pi+pi- decay double suppressed by the G-parity and OZI rule is measured Br(phi to pi+pi-pi+pi-) = (3.93 +- 1.74 +- 2.14) \cdot 10^{-6}. The upper limits have been placed for the decays phi to pi+pi-pi+pi-pi0 and phi to eta pi+pi- Br(phi to pi+pi-pi+pi-pi0) < 4.6 \cdot 10^{-6} 90% CL, Br(phi to eta pi+pi-) < 1.8 \cdot 10^{-5} 90% CL.