  In this work we study electron side-injection and trapping in the blow-out
regime in deep plasma channels. We analyze the maximum angle of injection, for
which at least 90\% of the injected electrons are trapped. We discuss the
dependence of this angle on the electrons' initial energy and their injection
positions. In the scope of a semi-analytical blow-out model we show that the
injection position is a less critical factor for trapping if electrons are
injected into deep plasma channels. PIC simulations and analytical
approximations support our results from the semi-analytical model.
