Precision studies of the Higgs boson decay channel H→ZZ→4ℓ with MEKD

The importance of the H -> ZZ* -> 4l "golden" channel has recently been proven by its major role in the discovery, by the ATLAS and CMS collaborations, of an apparently Higgs-like resonance with mass near 125 GeV. Much previous phenomenological work on this channel focuses on its use in determining the spin and CP properties of a purported Higgs boson. Significantly less attention has been paid to the logically prior question of distinguishing signal from background events in this channel, which is especially important for a 125 GeV Higgs boson. We show the advantages of using a multivariate analysis, such as the Matrix Element Method (MEM) that will be discussed here, in separating the Higgs signal from the irreducible Standard Model background. We discuss a number of issues that may arise in the use of the MEM and compare existing leading order MEM-based approaches and software. We also provide a code to calculate a kinematic discriminant, KD, based on the full leading order matrix elements, which would aid experimentalists and phenomenologists in their continuing studies of the "golden" Higgs channel. The code contains the most general parameterization of the couplings of a spin zero resonance and can be used for studies of its properties as well.