Measurement of transversal handedness in 3π diffractive production

Some years ago the concept of handedness (H) was introduced as a measure of polarization of parent partons or hadrons. It was defined as an asymmetry of a process probability W with respect to an axial vector projection and was shown to be proportional to polarization P. In this work the transversal handedness of diffractively produced pion triples π-+A→(π-π+π-)+A by π- beam 40 GeV/c from a different nucleus A is studied. It is defined as HT1=(W(Nn>0)-W(Nn<0)/W(Nn>0)+W(Nn<0))=αP where N is a normal to the production plane of the pion triple, N=(v3πxvb) (vb and v3π are velocities of the initial π- beam and the 3 pion center of mass) and n is a normal to the 'decay plane' of the triple in its center of mass. The value of the asymmetry, averaged over all nuclei is HT1=(5.96±0.21)%. The dependence of the handedness on atomic number, Feynmann variable, transversal momentum and on invariant mass of the neutral pion pair and of the pion triple were investigated. The former resembles the single spin asymmetry behavior while the latter has rich resonance structure and show clear dynamic origin of the handedness. For more details see Phys. Atom. Nucl. 63 (2000) 445; nucl-th/9901005