Massive quark polarization in Quantum Chromodynamics subprocesses.

摘要

It is well known that the single polarization asymmetries are large in hyperon production in contrast with naive Quantum Chromodynamics predictions. We have explored the possibility of polarization of quarks in QCD subprocesses, assuming that the quark mass can be significant at energies of interest. The fourth order contribution to the single spin asymmetry in each important subprocess for strange quark production is calculated. Mass dependence and the kinematical properties of the polarization of the strange quark in the partons' center-of-mass frame are discussed. The s-quark polarization in the hadrons' center-of-mass frame is obtained by performing the convolution integrations with the initial state parton distribution functions. A fit to the hyperon polarization is presented that reproduces the unique and striking kinematic dependence of the data. This is evidence that the ''seed'' of the polarization is in the basic scattering process and it is dominated by the gluon fusion subprocess. 31 figs.