Phenomenology of Photon-Jets
  One of the challenges of collider physics is to unambiguously associate detector based objects with the corresponding elementary physics objects. A particular example is the association of calorimeter-based objects such as "jets", identified with a standard (IR-safe) jet algorithm, with the underlying physics objects, which may be QCD-jets (arising from a scattered parton), electrons, photons and, as discussed here, photon-jets (a group of collinear photons). This separation is especially interesting in the context of Higgs searches, where the signal includes both di-photon (in the Standard Model) and di-photon-jet decays (in a variety of Beyond the Standard Model scenarios), while QCD provides an ever-present background. Here we describe the implementation of techniques from the rapidly evolving area of jet-substructure studies to not only enhance the more familiar photon-QCD separation, but also separately distinguish photon-jets, i.e., separate usual jets into three categories: single photons, photon-jets and QCD. The efficacy of these techniques for separation is illustrated through studies of simulated data. 
Stephen D. Ellis, Tuhin S. Roy, and Jakub Scholtz
hep-ph hep-ex