π+ → π+π± on deuterium at Tπ+ = 283 MeV

Abstract

New experimental results on the π + d → π + π − pp and π + d → π + π + nn reactions at T π 1 = 283 MeV are presented. In-plane coincidence data were taken with the CHAOS spectrometer using pions from the M11 channel at TRIUMF. Because of the quasi-free nature of the pion-production reaction, the present study is equivalent to studying the elementary π + N → π + π ± N reactions on protons and neutrons simultaneously. These exclusive measurements provide a set of many-fold differential cross sections which are an ideal testing ground for microscopic models describing the πN → ππN reaction. The interpretation of the data relies on a model which is based on effective chiral Lagrangians to describe the piece of the reaction that includes only π's and N's, and on effective Lagrangians to account for intermediate Δ's and N ∗' s . The measured many-fold differential cross sections are used to constrain some parameters of the model (ξ, f Δ , C, g N ∗ Δπ and g N ∗Nπ ). Finally, the π + π ± invariant mass distributions display no evidence of strongly interacting pion pairs in either the I = J = 0 or the I = 2 J = 0 channels.