New LEP bounds on B-violating scalar couplings: R-parity violating supersymmetry or diquarks

We use the precision electroweak data at LEP to place bounds on B-violating Yukawa couplings, two theoretically appealing examples being provided by R-parity violating supersymmetry and diquarks. The couplings involving the third generation quarks are most severely constrained. These bounds are complementary to those obtained from low-energy processes.