New constraints onR-parity violation fromKandBsystems

Abstract
We have derived new upper limits on several products (two at a time) of lepton number violating �'-type couplings from the consideration ofS = 2 andB = 2 box graphs. Each box contains one scalar lepton and one W-boson or one charged-Higgs-boson as internal lines. Most of these bounds are more stringent than previously obtained. Some of these product couplings drive KL (and some other Bd) decays to two charged leptons at enhanced rates. Some of them can explain the rare K+ ! �+�¯ � event recently observed at BNL.