Production and decay of the Δ(970) and D(1285) mesons in π^±p interactions at 16 GeV/c

The production of the Δ(970) and D(1285) mesons is observed in 6- and 7-body π^±p reactions at 16 GeV/c. The Δ(970) is found to decay into ηπ and in addition a sharp rise in the (K⁰K^±) mass distribution at threshold may be attributed to the decay of the Δ into KK. For the branching ratio (Δ → KK)/(Δ → ηπ) a lower limit of 0.08 was estimated. The D-meson is observed to decay into ρ{variant}ππ and ηππ; the ηππ mode proceeds mainly via the decay chain D → Δπ → ηππ. The branching ratios (D → ρ{variant}ππ) /ar (D → ghππ) and (D → KKπ)/(D → ηππ) < 0.26 are found. The mass M and width Γ of the Δ are 977 ± 7 MeV and 44 ± 22 MeV, respectively, while for the D-meson the ρ{variant}ππ and ηππ decay modes averaged give M = 1279 ± 5 MeV and Γ = 24 ± 18 MeV, taking into account the experimental resolution. The production mechanism of the reaction π^±p → π^±Dp is discussed. Spin and parity of the Δ(970) and D(1285) are investigated. Evidence is also found for the production of the η′(958) mespn decaying into ηππ while for the ηππ and KKπ decay modes of the E(1420) meson only indications are seen.