Signatures of Scalar Top with R-parity Breaking Coupling at HERA

In the framework of the minimal supersymmetric standard model with an R-parity breaking coupling of the scalar top quark (stop) we investigate production processes and decay properties of the stop at HERA energies. The model is characterized by a light stop possibly lighter than the other squarks. We show that the stop could be singly produced not only in the neutral current processes but also in associated processes whose final states contain some heavy flavor quarks, bottom and top quarks. These signatures would be useful to discriminate the stop from leptoquarks.