  There is a strong correlation between the $p_T$ and isolation of the lepton
coming from $B$ decay. Consequently the isolated lepton background from $B$
decay goes down rapidly with increasing lepton $p_T$; and there is a $p_T$
cutoff beyond which it effectively vanishes. For the isolation cut of $E^{AC}_T
< 10$ GeV, appropriate for LHC, the lepton $p_T$ cutoff is 80 GeV. This can be
exploited to effectively eliminate the $B$ background from the like sign
dilepton channel apropriate for Majorana particle searches, as well as the
unlike sign dilepton and the single lepton channels appropriate for the top
quark search. We illustrate this with a detailed analysis of the $B$ background
in these channels along with the signals at LHC energy using both parton level
MC and ISAJET programs.
