Angular asymmetries in the reactions $$\vec pp \to d\pi ^ + \eta $$ and $$\vec pn \to d\pi ^0 \eta $$ and a 0-f 0 mixing

Abstract

The reactions pp → dπ + η and pn → dπ 0 η are of special interest for investigating the a 0(980) (J P=0+) resonance in the process NN → da 0 → dπη. We study some aspects of those reactions within a general formalism and also in a concrete phenomenological model. In particular, it is shown that the presence of nonresonant (i.e., without excitation of the a 0 resonance) contributions to these reactions yields nonvanishing values for specific polarization observables, i.e., to effects like those generated by a 0 0 -f 0 mixing. An experimental determination of these observables for the reaction $$\vec pp \to d\pi ^ + \eta $$ would provide concrete information on the magnitude of those nonresonant contributions to πη production. We also discuss the possibility of extracting information about a 0 0 -f 0 mixing from the reaction $$\vec pn \to d\pi ^0 \eta $$ with a polarized proton beam.