A γγ collider for the 750 GeV resonant state

Recent data collected by ATLAS and CMS at 13 TeV collision energy of the LHC indicate the existence of a new resonant state ϕ with a mass of 750 GeV decaying into two photons γγ. The properties of ϕ   should be studied further at the LHC and also future colliders. Since only ϕ→γγϕ→γγ decay channel has been measured, one of the best ways to extract more information about ϕ is to use a γγ collider to produce ϕ at the resonant energy. In this work we show how a γγ collider helps to verify the existence of ϕ and to provide some of the most important information about the properties of ϕ  , such as branching fractions of ϕ→V1V2ϕ→V1V2. Here ViVi can be γ, Z  , or W±W±. We also show that by studying angular distributions of the final γ  's in γγ→ϕ→γγγγ→ϕ→γγ, one can obtain crucial information about whether this state is a spin-0 or a spin-2 state.