Energy dependence of hadron polarization in $e^+e^-\to hX$ at high energies

Abstract

The longitudinal polarization of hyperons in $e^+e^-$ annihilation at high energies depends on the longitudinal polarization of the quark produced at the $e^+e^-$ annihilation vertex whereas the spin alignment of vector mesons is independent of it. They exhibit very different energy dependences. We use the longitudinal polarization of Lambda hyperon and the spin alignment of $K^*$ as examples and present numerical results of energy dependences. We present the results at the leading twist with perturbative QCD evolutions of fragmentation functions at the leading order.