Neutral top-pion and $tγ(z)$ production at the HERA and THERA colliders

Abstract

In the context of top-color assisted technicolor ($TC2$) models, we calculate the contributions of the neutral top-pion $ π_{t}^{0}$ to $tγ$ and $tz$ production via the processes $ ep\to γc \to tγ$ and $ ep\to γc \to tz$ at the $HERA$ and $THERA$ colliders. Our results show that the cross sections $σ_{tγ}(s)$ and $σ_{tz}(s)$ are very small at the $HERA$ collider with $\sqrt{s}=320GeV $. However, in most of the parameter space, $σ_{tγ}(s)$ or $σ_{tz}(s)$ is in the range of about $0.1pb \sim 1 pb$ at the $THERA$ collider with $\sqrt{s}=1000GeV$.