B-]TAU(-)(X) DECAYS - FIRST CONSTRAINTS AND PHENOMENOLOGICAL IMPLICATIONS()TAU()

The study of B --> tau(+)tau(-) (X) decays can provide us with a bette r understanding of the third generation, and can be a useful probe uf physics beyond the standard model. We present a model-independent anal ysis of these decays. We classify new physics that can largely enhance the decay rates and we discuss the constraints implied by other proce sses. Experimentally, flavor-changing neutral current B decays into Gn at state tau's are still unconstrained. Searches for B decays with lar ge missing energy at CERN LEP provide the first limits. We estimate th at existing data already imply bounds on the B-d --> tau(+)tau(-), B-s --> tau(+)tau(-), and B --> X tau(+)tau(-) decay rates at the few per cent level. Although these bounds are over four orders of magnitude ab ove the standard model predictions, they provide the first constraints on some leptoquarks, and on some R-parity-violating couplings.