W- and Z-Boson Interactions in Supersymmetric Models with Explicit R-Parity Violation

The minimal supersymmetric Standard Model with explicit R-parity nonconservation contains bilinear terms involving the left-handed lepton superfields and the Higgs chiral multiplet with hypercharge Y=+1, which cannot in general be rotated away in the presence of soft-supersymmetry- breaking interactions. These bilinear lepton-number-violating terms are found to give rise to non-zero vacuum expectation values of the scalar neutrinos. This leads to nonuniversal and flavour-violating tree-level couplings of the W and Z bosons to charged leptons and neutrinos. The parameter space of this novel scenario is systematically analyzed and further restricted by a number of laboratory, astrophysical, and cosmological constraints. The possibility that our minimal model can account for the KARMEN anomaly is examined.