The ϱ radiative decay width: a measurement at 200 GeV

Abstract The ϱ − radiative decay width has been measured by studying the production of ϱ − via the Primakoff effect by 200 GeV incident π − on Cu and Pb targets. This width was obtained by fitting the measured d σ /d t for ϱ production with the theoretical coherent differential cross section including both the electromagnetic and strong contributions. The measured radiative width value is 81 ± 4 ± 4 keV: it is consistent with the ratio Γ(ϱ → πγ)/Γ(ω → πγ) ∼ case:1 9 as expected from the vector dominance and the quark model.