Extraction of CP Properties of the H(125) Boson Discovered in Proton-Proton Collisions at $\sqrt{s}$ = 7 and 8 TeV with the CMS Detector at the LHC

In this thesis we build a novel analysis framework to perform the direct extraction ofall possible effective Higgs boson couplings to the neutral electroweak gauge bosonsin the H → ZZ (∗) → 4 channel also referred to as the golden channel. We use analytic expressions of the full decay differential cross sections for the H → V V → 4process, and the dominant irreducible standard model q q → 4 background where¯4 = 2e2µ, 4e, 4µ. Detector effects are included through an explicit convolution ofthese analytic expressions with transfer functions that model the detector responsesas well as acceptance and efficiency effects. Using the full set of decay observables, weconstruct an unbinned 8-dimensional detector level likelihood function which is continuous in the effective couplings, and includes systematics. All potential anomalouscouplings of HV V where V = Z, γ are considered, allowing for general CP even/oddadmixtures and any possible phases. We measure the CP -odd mixing between thetree-level HZZ coupling and higher order CP -odd couplings to be compatible withzero, and in the range [−0.40, 0.43], and the mixing between HZZ tree-level couplingand higher order CP -even coupling to be in the ranges [−0.66, −0.57] ∪ [−0.15, 1.00];namely compatible with a standard model Higgs. We discuss the expected precisionin determining the various HV V couplings in future LHC runs. A powerful and atfirst glance surprising prediction of the analysis is that with 100-400 fb−1 , the goldenchannel will be able to start probing the couplings of the Higgs boson to diphotons inthe 4 channel. We discuss the implications and further optimization of the methodsfor the next LHC runs.