R_b and R_l in MSSM without R-Parity

We examined Z\ell^+\ell^- and Zb\bar b couplings in the minimal supersymmetric model (MSSM) with explicit R-parity violating interactions. We found the top quark L-violating couplings \lambda'_{i3k} and B-violating couplings \lambda''_{3j3} could give significant contributions through the top quark loops. To accomadate the latest R_{\ell} data, \lambda'_{i3k} are suject to stringent bounds, some of which can be much stronger than the current bounds. Within the current perturbative unitarity bound of 1.25 for \lambda''_{3j3}, the R_b value in R-violating MSSM agrees well with the experimental data at $2\sigma$ level, but may lie outside the 1\sigma range depending on the involved sfermion mass.Comment: results update

Top-squark mixing effects in the supersymmetric electroweak corrections to top quark production at the Tevatron

Taking into account the mixing effects between left- and right-handed top-squarks, we calculate the genuine supersymmetric eletroweak correction to top quark production at the Tevatron in the minimal supersymmetric model. The analytic expressions of the corrections to both the parton level cross section and the total hadronic cross section are presented. Some numerical examples are also given to show the size of the corrections.Comment: 11 pages, 3 figures, available at reques