The first set of proton-proton collisions at 13 TeV at the LHC showed a tantalizing hint of new physics – an excess of events with two photons produced at an invariant mass of 750 GeV. Subsequently, over 500 papers appeared on the arXiv suggesting that this signal was being caused by the decay of a new particle beyond the standard model.
In the most recent LHC data this signal has disappeared. However, the exercise of building the 750 GeV models illustrated general principles about the kinds of new physics that the LHC might discover in future. In this seminar, I will talk about drastically different theories that were proposed to underlie the diphoton process, and the tight constraints they had to satisfy in order to be consistent with this and earlier observations.