Study of s- and t-channel helicity conservation in the diffractive part of the reaction π±p→ π(N π) at 16 GeV/ c

Abstract

By means of an isospin analysis of the reaction π ±p→ π(N π) at 16 GeV/ c we have determined the decay angular distributions of the N π system with I= 1 2 produced by isospin zero exchange. Helicity conservation is not observed in the t-channel for the N π mass region below 1.6 GeV, where diffraction dissociation of the proton is supposed to dominate. There are indications for approximate t-channel helicity conservation for N ∗ (1690) production. In the helicity frame, the experimental data are not in agreement with s-channel helicity conservation over the whole N π mass range investigated. Thus the diffractive process N→N π differs both from the process N→N ππ (or π→ πππ and K→K ππ) which approximately conserves t-channel helicity and from the elastic scattering N→N which conserves helicity in the s-channel.