Spin Alignment of Vector Mesons in Polarized and Unpolarized High Energy Reactions

Abstract

Recent e+e- annihilation experiments show a striking spin alignment of vector mesons produced in the fragmentation of a polarized quark.We show that these data imply a simple relation between the polarization of the anti-quark, which is produced in the fragmentation process to combine with the fragmenting quark to form the meson, and that of the fragmenting quark. After having obtained a good fit to the e+e- data, we extend the calculations to lepton-nucleon and nucleon-nucleon collisions with polarized beams. We also discuss the relation between the spin alignment of vector meson in unpolarized hadron-hadron collisions and the single-spin left-right asymmetry. We make predictions for the polarization of the vector mesons in these reactions which can be checked by future experiments.