  The presence of large-mass resonances in the data collected at the Large
Hadron Collider would provide direct evidence of physics beyond the Standard
Model. A key challenge in current resonance searches at the LHC is the
modelling of signal--background interference effects, which can severely
distort the shape of the reconstructed invariant mass distribution relative to
the case where there is no interference. Such effects are strongly dependent on
the beyond the Standard Model theory that must be considered as unknown if one
aims to minimise any theoretical bias on the search results. In this paper, we
describe a procedure which employs a physically-motivated, model-independent
template functional form that can be used to model interference effects, both
for the characterisation of positive discoveries, and in the presentation of
null results. We illustrate the approach with the example of a scalar resonance
decaying into a pair of photons.
