Measurement of the isospin amplitude [formula omitted] in the reaction γn → ϱ0(p π−) at 7.5 GeV

Abstract

The cross-channel isospin amplitude ∣M 0 1 2 ∣ is measured in the single reaction γn → ϱ 0(p π −) at 7.5 GeV assuming the ϱ 0 dominance model. A low-mass enhancement is found for ∣M 0 1 2 ∣ 2 in the range of m(p π −) of ∼1.2 to ∼1.7 GeV. The reaction strongly violates s-channel helicity conservation but is consistent with t-channel helicity conservation. The ∣M 0 1 2 ∣ features are found to be very similar to those obtained in previous analyses of πp → π(N π) reactions.