  We introduce a new class of infrared safe jet observables, which we refer to
as template overlaps, designed to filter targeted highly boosted particle
decays from QCD jets and other background. Template overlaps are functional
measures that quantify how well the energy flow of a physical jet matches the
flow of a boosted partonic decay. Any region of the partonic phase space for
the boosted decays defines a template. We will refer to the maximum functional
overlap found this way as the template overlap. To illustrate the method, we
test lowest-order templates designed to distinguish highly-boosted top and
Higgs decays from backgrounds produced by event generators. For the functional
overlap, we find good results with a simple construction based on a Gaussian in
energy differences within angular regions surrounding the template partons.
Although different event generators give different averages for our template
overlaps, we find in each case excellent rejection power, especially when
combined with cuts based on jet shapes. The template overlaps are capable of
systematic improvement by including higher order corrections in the template
phase space.
