Master thesis defence by Kristoffer Levin Hansen

Title: Search for new physics in diphoton production with the ATLAS detector at the LHC

Abstract: In this thesis, we will conduct a search for physics beyond the Standard Model by introducing into it, via the effective Lagrangian approach, a new qqgamma gamma contact interaction. The effects of this new interaction on the distribution of invariant masses of diphotons will be assessed via the production of Monte Carlo simulations at two values of the associated mass scale Λ, and a corresponding Monte Carlo set for the Standard Model. These Monte Carlo sets will be subjected to full atlas detector stimulation, before they are compared with data taken by atlas during the 2012 8 TeV run of the LHC. A fully data driven back- ground estimation will be carried out on this data set. Finally, we will interpolate our Monte Carlo samples, so that we may compare a distribution corresponding to any Λ with the experimental distribution. This can be used for a maximum profile likelihood fit of Λ to data.