LEP- and low energy-bounds on R-parity-violating supersymmetric Yukawa couplings

Abstract

Electroweak precision data at LEP are used to place bounds on some $\lambda'$-type ($L$-violating) and $\lambda''$-type ($B$-violating) $R$-parity violating supersymmetric Yukawa couplings. We consider one-loop corrections (triangles and self-energies) induced by these couplings to the $Z$-partial widths. The couplings involving the top quark induce stronger loop effects and hence are more strongly constrained than others. On the other hand, information on $D$- and $\tau$-decays are used to constrain some of the $\lambda'$-type couplings which are complementary to the ones constrained from LEP. Among the bounds we have derived, many are new from a phenomenological view-point.Comment: 2 pages, postscript (uucompressed), to appear in the Proceedings of the International Europhysics Conference on High Energy Physics, Brussels, 27 July - 2 August, 199