Remarks about top quark signals at pantip colliders

Conventional top signals at pantip colliders are based on leptons from semileptonic top decays t → blν. Three aspects are briefly discussed. (i) Lepton isolation is the usual way to suppress backgrounds from b and c decays, but the unknown b→u decays are more difficult to suppress than b →c; also theoretical and experimental isolation do not always correspond. (ii) W → lν decay is the principal remaining background; there are new ways to separate top signals that exploit the associated jet multiplicity, or dileptons, or both. (iii) If unconventional decays via real charged Higgs scalars t → bH+ occur, they could suppress conventional modes; however the subsequent decay H+ → antiτ ν plausibly has a big branching fraction and could generate observable signals (events with large missing PT, isolated τ- jet or letpon, two isolated τ- jets) at present pantip colliders