Precision studies of the Higgs boson decay channel<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>H</mml:mi><mml:mo>→</mml:mo><mml:mi>Z</mml:mi><mml:mi>Z</mml:mi><mml:mo>→</mml:mo><mml:mn>4</mml:mn><mml:mi>ℓ</mml:mi></mml:math>with MEKD

The importance of the $H\ensuremath{\rightarrow}ZZ\ensuremath{\rightarrow}4\ensuremath{\ell}$ ``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 $4e$ and $4\ensuremath{\mu}$ 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 $H\ensuremath{\rightarrow}ZZ\ensuremath{\rightarrow}4\ensuremath{\ell}$ channel.