ISSN - 03702693, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 1999, vol. 462, p. 371-379
First observation of the φ → π+ π- γ decay
Radiative decays of the φ meson have been studied using a data sample of about 20 million φ decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From selected e+e-→ π+π-γ events the φ → π+π-γ decay has been observed for the first time. Under the assumption that the intermediate f0(980)γ state dominates in the φ → π+π-γ decay, the corresponding branching ratio is Br(φ→f0(980)γ) = (1.93 ± 0.46 ± 0.50) × 10-4. Selected e+e-→ μ+μ-γ events were used to obtain Br(φ→ μ+μ-γ) = (1.43 ± 0.45 ± 0.14) × 10-5 for Eγ > 20 MeV. Using the same data sample, upper limits at 90% CL have been obtained for the C-violating decay of the φ: Br(φ→ ργ) < 1.2 × 10-5; and for the P- and CP-violating decay of the η: Br(η→π+π-) <3.3 × 10-4. © 1999 Published by Elsevier Science B.V. All rights reserved.