πℓ2, Kℓ3and K0−K0 constraints on leptoquarks and supersymmetric particles

Mass bounds from different processes for charged Higgs particles, for pseudoscalar leptoquarks occurring in dynamically broken theories, for vector leptoquarks occurring in the Pati-Salam type of grand unified theories and for the exotic particles of supersymmetric theories are studied. The processes considered are the π → eν to π → μν branching ratio, the CP-violating K?3 decay parameters, and the CP-violating part of the K_L ? K_S mass difference. The π → eν to π → μν branching ratio sets the most stringent bounds, 0.5 TeV for charged Higgs particles, 1 TeV for pseudoscalar leptoquarks, 125 TeV for vector leptoquarks and 0.1–1 TeV for the supersymmetric partners of ordinary particles. The π?2 branching ratio should be sensitive at the present experimental accuracy to the effects of pseudoscalar leptoquarks.