Abstract
The importance of the H -> ZZ -> 4l "golden" channel was shown by its major role in the discovery, by the ATLAS and CMS collaborations, of a Higgs-like boson with mass near 125 GeV. We analyze the discrimination power of the matrix element method both for separating the signal from the irreducible ZZ background and for distinguishing various spin and parity hypotheses describing a signal in this channel. We show that the proper treatment of interference effects associated with permutations of identical leptons in the four electron and four muon final states plays an important role in achieving the best sensitivity in measuring the properties of the newly discovered boson. We provide a code, MEKD, that calculates kinematic discriminants based on the full leading order matrix elements and which will aid experimentalists and phenomenologists in their continuing studies of the H -> ZZ -> 4l channel.
Highlights
The CERN LHC collaborations recently reported the observation of a new bosonic particle with mass m ∼ 125 GeV1,2
MATRIX ELEMENT KINEMATIC DISCRIMINANT (MEKD), that calculates kinematic discriminants based on the full leading order matrix
For the analyses described below, we use parton-level events generated with MadGraph[54,64,65]
Summary
The CERN LHC collaborations recently reported the observation of a new bosonic particle with mass m ∼ 125 GeV1,2. The instructions on how to install and run the code are given in Appendix C This code calculates matrix elements and kinematic discriminants, natively including diagrams with swapped identical leptons (and the associated interference) in the 4e and 4μ final states, background diagrams with γ∗ propagators for the “doubly resonant” qq → ZZ → 4l process and singly resonant qq → Z → 4l production[62]. It does not use a narrow width approximation for either the Z bosons or the signal resonance
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