Analyzing power measurements for the (. pi. sup + ,. pi. sup 0 ) reaction on a polarized sup 13 C target

Abstract

The analyzing powers A{sub y} differential cross sections d{sigma}/d{Omega} for the reaction {sup 13}C({pi}{sup +},{pi}{sup 0}){sup 13}N have been measured for forward scattering angles at an incident pion kinetic energy of T{sub pi}{sup +} = 163 MeV by using a transversely polarized target. Analyzing powers and reaction cross sections impose stringent constrains on nuclear reaction models and can be used to test the present understanding of nuclear structure for 1p-shell nuclei. The resulting A{sub y} are compared to the predictions of first-order Distorted Wave Impulse Approximation (DWIA) calculations, which reproduce well the differential cross sections. Although there is qualitative agreement at forward angles, the quantitative agreement is poor, especially at scattering angles larger than 50{degrees}. Since the DWIA calculations do not appear to be strongly sensitive to the assumed nuclear structure model, the discrepancy in describing the analyzing powers suggests that the reaction mechanism may not yet be well understood and higher order corrections may be important. Also measured were the analyzing powers for the elementary charge exchange reaction {pi}{sup {minus}} {bar p} {yields} {pi}{degrees}n over the same angular range and at an incident pion kinetic energy of T{sub pi}{minus} = 161 MeV. The results are compared to the mostmore » recents phase shift predictions. Within the experimental uncertainties, phase shift calculations agree with the measured A{sub y} and no changes in the {pi}N phase shifts near the P{sub 33} resonance are needed to describe the data.« less