Top-quark production in hadron-hadron collisions and anomalous top-quark–gluon couplings

We discuss the influence of anomalous tt¯G couplings on total and differential tt¯ production cross sections in hadron-hadron collisions. We study in detail the effects of a chromoelectric and a chromomagnetic dipole moment ${\mathit{d}}_{\mathit{t}}^{\prime }$ and ${\mathrm{\mu }}_{\mathit{t}}^{\prime }$ of the top quark. We estimate the values of ${\mathit{d}}_{\mathit{t}}^{\prime }$ and ${\mathrm{\mu }}_{\mathit{t}}^{\prime }$ which are allowed by the present Fermilab Tevatron experimental results on top-quark production in pp¯ collisions. In the ${\mathrm{\mu }}_{\mathit{t}}^{\prime }$-${\mathit{d}}_{\mathit{t}}^{\prime }$ plane, we find a whole region where the anomalous couplings give a zero net contribution to the total top-quark production rate. In differential cross sections, the anomalous moments have to be quite sizable to give measurable effects. A chromoelectric dipole moment of the top quark violates CP invariance. We discuss a CP-odd observable O${\mathrm{^}}_{\mathit{L}}$ which allows for a direct search for CP violation in top-quark production. We find that the presence of a chromomagnetic moment ${\mathrm{\mu }}_{\mathit{t}}^{\prime }$ can influence the sensitivity of O${\mathrm{^}}_{\mathit{L}}$ to ${\mathit{d}}_{\mathit{t}}^{\prime }$ considerably. © 1996 The American Physical Society.