  We study the possibility of detecting New Physics (NP) phenomena at the LHC
through a new search strategy looking at the monotop (top plus missing energy)
signature which is common to a variety of NP models. We focus on the leptonic
top decay mode and study the discovery or exclusion reach of the 2012 LHC data
for three example models. Contrary to the hadronic mode, in this case the
problematic QCD multijet background can be safely neglected. We find that the
key kinematic variable to suppress most of the remaining SM backgrounds is the
transverse mass of the charged lepton and missing energy. In fact, one could
expect that the single-top production measurements already address the monotop
signature in this mode. This is however not the case because in the SM
single-top production the transverse mass has an end point determined by the W
mass, while the NP signals typically have an additional source of missing
energy. We compare, under the same conditions, our monotop search strategy with
existing single-top measurements and find a considerable improvement in the
monotop signature reach.
