Test of helicity conservation and spin-parity analysis of the N∗(1700)

Abstract The diffractively produced low-mass π + π − p system isstudied in the reaction π ± p → π ± π + π − p. We observe strong N ∗ (1700) production and determine the branching fraction to π − Δ ++ to be 65 ± 15%. A spin-parity analysis (assuming J 7 2 ) yields J P = 5 2 + for the N ∗ (1700). The study of the decay angular distribution of the N ∗ (1700) indicates that helicity is conserved in the t -channel rather than in the s -channel.