Radiative decay of the Δ resonance: Analyzing powers forπ−p→→γn

Abstract

The polarized target asymmetry ${\mathit{A}}_{\mathit{N}}$ for ${\mathrm{\pi }}^{\mathrm{-}}$p→→γn has been measured by coincident detection of the γ and the neutron at several angles across the Δ resonace energy region. A high-resolution NaI γ spectrometer together with good time-of-flight information for the neutron resulted in excellent separation of this radiative capture reaction from the much higher cross-section charge exchange reaction ${\mathrm{\pi }}^{\mathrm{-}}$p→→${\mathrm{\pi }}^0$n. Statistical uncertainties are Δ${\mathit{A}}_{\mathit{N}}$=0.02-0.04, representing a significant improvement over previous results. The new data are discussed in the context of recent theoretical models.