Single quark polarization in quantum chromodynamics subprocesses

Abstract

It is well known that the single-polarization asymmetries vanish in QCD with massless quarks. But, heavy quarks with a nonzero mass should be transversely polarized due to the breakdown of the helicity conservation. In this paper we give the exact fourth-order perturbative QCD predictions for the transverse polarization from all QCD subprocesses, q+q\ensuremath{'}\ensuremath{\rightarrow}q+q\ensuremath{'}, q+g\ensuremath{\rightarrow}q+g, g+g\ensuremath{\rightarrow}q+q\ifmmode\bar\else\textasciimacron\fi{}, and q+q\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}q\ensuremath{'}+q\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{'}, which are significant for heavy quark production, with a description of the method of calculation. The kinematical dependence of the polarization is discussed. Top quark polarization from gluon fusion and quark annihilation processes, which are the important subprocesses at high energies, is estimated and its significance is discussed. \textcopyright{} 1996 The American Physical Society.