Leptoquark Pair Production at $ep$ Colliders

The pair production cross section for scalar and vector leptoquarks at $ep$ colliders is calculated for the case of photon–gluon fusion. In a model independent analysis we consider the most general $C$ and $P$ conserving couplings of gluons and photons to both scalar and vector leptoquarks described by an effective low–energy Lagangian which obeys $U(1{)}_{em}\times SU(3{)}_c$ invariance. Numerical predictions are given for the kinematical regime at HERA and LEP~$\otimes$~LHC.