Top-quark pair production via polarized and unpolarized protons in the supersymmetric QCD

The QCD corrections to the top-quark pair production via both polarized and unpolarized gluon fusion in $pp$ collisions are calculated in the Minimal Supersymmetric Model(MSSM). We find the MSSM QCD corrections can reach 4% and may be observable in future precise experiments. Furthermore, we studied the CP violation in the MSSM, our results show that the CP violating parameter is sensitive to the masses of SUSY particles (It becomes zero, when the c.m. energy is less than twice the masses of both gluino and stop quarks.) and may reach $10^{-3}$.